After commit dcb0b5575d ("tracing: Remove TRACE_EVENT_FL_USE_CALL_FILTER
logic"), no one's going to set the TRACE_EVENT_FL_FILTERED or change the
call->filter, so remove related logic.
Link: https://lore.kernel.org/20240911010026.2302849-1-zhengyejian@huaweicloud.com
Signed-off-by: Zheng Yejian <zhengyejian@huaweicloud.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
There is another found exception that the "timerlat/1" thread was
scheduled on CPU0, and lead to timer corruption finally:
```
ODEBUG: init active (active state 0) object: ffff888237c2e108 object type: hrtimer hint: timerlat_irq+0x0/0x220
WARNING: CPU: 0 PID: 426 at lib/debugobjects.c:518 debug_print_object+0x7d/0xb0
Modules linked in:
CPU: 0 UID: 0 PID: 426 Comm: timerlat/1 Not tainted 6.11.0-rc7+ #45
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
RIP: 0010:debug_print_object+0x7d/0xb0
...
Call Trace:
<TASK>
? __warn+0x7c/0x110
? debug_print_object+0x7d/0xb0
? report_bug+0xf1/0x1d0
? prb_read_valid+0x17/0x20
? handle_bug+0x3f/0x70
? exc_invalid_op+0x13/0x60
? asm_exc_invalid_op+0x16/0x20
? debug_print_object+0x7d/0xb0
? debug_print_object+0x7d/0xb0
? __pfx_timerlat_irq+0x10/0x10
__debug_object_init+0x110/0x150
hrtimer_init+0x1d/0x60
timerlat_main+0xab/0x2d0
? __pfx_timerlat_main+0x10/0x10
kthread+0xb7/0xe0
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2d/0x40
? __pfx_kthread+0x10/0x10
ret_from_fork_asm+0x1a/0x30
</TASK>
```
After tracing the scheduling event, it was discovered that the migration
of the "timerlat/1" thread was performed during thread creation. Further
analysis confirmed that it is because the CPU online processing for
osnoise is implemented through workers, which is asynchronous with the
offline processing. When the worker was scheduled to create a thread, the
CPU may has already been removed from the cpu_online_mask during the offline
process, resulting in the inability to select the right CPU:
T1 | T2
[CPUHP_ONLINE] | cpu_device_down()
osnoise_hotplug_workfn() |
| cpus_write_lock()
| takedown_cpu(1)
| cpus_write_unlock()
[CPUHP_OFFLINE] |
cpus_read_lock() |
start_kthread(1) |
cpus_read_unlock() |
To fix this, skip online processing if the CPU is already offline.
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20240924094515.3561410-4-liwei391@huawei.com
Fixes: c8895e271f ("trace/osnoise: Support hotplug operations")
Signed-off-by: Wei Li <liwei391@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
stop_kthread() is the offline callback for "trace/osnoise:online", since
commit 5bfbcd1ee5 ("tracing/timerlat: Add interface_lock around clearing
of kthread in stop_kthread()"), the following ABBA deadlock scenario is
introduced:
T1 | T2 [BP] | T3 [AP]
osnoise_hotplug_workfn() | work_for_cpu_fn() | cpuhp_thread_fun()
| _cpu_down() | osnoise_cpu_die()
mutex_lock(&interface_lock) | | stop_kthread()
| cpus_write_lock() | mutex_lock(&interface_lock)
cpus_read_lock() | cpuhp_kick_ap() |
As the interface_lock here in just for protecting the "kthread" field of
the osn_var, use xchg() instead to fix this issue. Also use
for_each_online_cpu() back in stop_per_cpu_kthreads() as it can take
cpu_read_lock() again.
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20240924094515.3561410-3-liwei391@huawei.com
Fixes: 5bfbcd1ee5 ("tracing/timerlat: Add interface_lock around clearing of kthread in stop_kthread()")
Signed-off-by: Wei Li <liwei391@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
osnoise_hotplug_workfn() is the asynchronous online callback for
"trace/osnoise:online". It may be congested when a CPU goes online and
offline repeatedly and is invoked for multiple times after a certain
online.
This will lead to kthread leak and timer corruption. Add a check
in start_kthread() to prevent this situation.
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20240924094515.3561410-2-liwei391@huawei.com
Fixes: c8895e271f ("trace/osnoise: Support hotplug operations")
Signed-off-by: Wei Li <liwei391@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This pull request contains the following branches:
context_tracking.15.08.24a: Rename context tracking state related
symbols and remove references to "dynticks" in various context
tracking state variables and related helpers; force
context_tracking_enabled_this_cpu() to be inlined to avoid
leaving a noinstr section.
csd.lock.15.08.24a: Enhance CSD-lock diagnostic reports; add an API
to provide an indication of ongoing CSD-lock stall.
nocb.09.09.24a: Update and simplify RCU nocb code to handle
(de-)offloading of callbacks only for offline CPUs; fix RT
throttling hrtimer being armed from offline CPU.
rcutorture.14.08.24a: Remove redundant rcu_torture_ops get_gp_completed
fields; add SRCU ->same_gp_state and ->get_comp_state
functions; add generic test for NUM_ACTIVE_*RCU_POLL* for
testing RCU and SRCU polled grace periods; add CFcommon.arch
for arch-specific Kconfig options; print number of update types
in rcu_torture_write_types();
add rcutree.nohz_full_patience_delay testing to the TREE07
scenario; add a stall_cpu_repeat module parameter to test
repeated CPU stalls; add argument to limit number of CPUs a
guest OS can use in torture.sh;
rcustall.09.09.24a: Abbreviate RCU CPU stall warnings during CSD-lock
stalls; Allow dump_cpu_task() to be called without disabling
preemption; defer printing stall-warning backtrace when holding
rcu_node lock.
srcu.12.08.24a: Make SRCU gp seq wrap-around faster; add KCSAN checks
for concurrent updates to ->srcu_n_exp_nodelay and
->reschedule_count which are used in heuristics governing
auto-expediting of normal SRCU grace periods and
grace-period-state-machine delays; mark idle SRCU-barrier
callbacks to help identify stuck SRCU-barrier callback.
rcu.tasks.14.08.24a: Remove RCU Tasks Rude asynchronous APIs as they
are no longer used; stop testing RCU Tasks Rude asynchronous
APIs; fix access to non-existent percpu regions; check
processor-ID assumptions during chosen CPU calculation for
callback enqueuing; update description of rtp->tasks_gp_seq
grace-period sequence number; add rcu_barrier_cb_is_done()
to identify whether a given rcu_barrier callback is stuck;
mark idle Tasks-RCU-barrier callbacks; add
*torture_stats_print() functions to print detailed
diagnostics for Tasks-RCU variants; capture start time of
rcu_barrier_tasks*() operation to help distinguish a hung
barrier operation from a long series of barrier operations.
rcu_scaling_tests.15.08.24a:
refscale: Add a TINY scenario to support tests of Tiny RCU
and Tiny SRCU; Optimize process_durations() operation;
rcuscale: Dump stacks of stalled rcu_scale_writer() instances;
dump grace-period statistics when rcu_scale_writer() stalls;
mark idle RCU-barrier callbacks to identify stuck RCU-barrier
callbacks; print detailed grace-period and barrier diagnostics
on rcu_scale_writer() hangs for Tasks-RCU variants; warn if
async module parameter is specified for RCU implementations
that do not have async primitives such as RCU Tasks Rude;
make all writer tasks report upon hang; tolerate repeated
GFP_KERNEL failure in rcu_scale_writer(); use special allocator
for rcu_scale_writer(); NULL out top-level pointers to heap
memory to avoid double-free bugs on modprobe failures; maintain
per-task instead of per-CPU callbacks count to avoid any issues
with migration of either tasks or callbacks; constify struct
ref_scale_ops.
fixes.12.08.24a: Use system_unbound_wq for kfree_rcu work to avoid
disturbing isolated CPUs.
misc.11.08.24a: Warn on unexpected rcu_state.srs_done_tail state;
Better define "atomic" for list_replace_rcu() and
hlist_replace_rcu() routines; annotate struct
kvfree_rcu_bulk_data with __counted_by().
-----BEGIN PGP SIGNATURE-----
iHUEABYIAB0WIQSi2tPIQIc2VEtjarIAHS7/6Z0wpQUCZt8+8wAKCRAAHS7/6Z0w
pTqoAPwPN//tlEoJx2PRs6t0q+nD1YNvnZawPaRmdzgdM8zJogD+PiSN+XhqRr80
jzyvMDU4Aa0wjUNP3XsCoaCxo7L/lQk=
=bZ9z
-----END PGP SIGNATURE-----
Merge tag 'rcu.release.v6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux
Pull RCU updates from Neeraj Upadhyay:
"Context tracking:
- rename context tracking state related symbols and remove references
to "dynticks" in various context tracking state variables and
related helpers
- force context_tracking_enabled_this_cpu() to be inlined to avoid
leaving a noinstr section
CSD lock:
- enhance CSD-lock diagnostic reports
- add an API to provide an indication of ongoing CSD-lock stall
nocb:
- update and simplify RCU nocb code to handle (de-)offloading of
callbacks only for offline CPUs
- fix RT throttling hrtimer being armed from offline CPU
rcutorture:
- remove redundant rcu_torture_ops get_gp_completed fields
- add SRCU ->same_gp_state and ->get_comp_state functions
- add generic test for NUM_ACTIVE_*RCU_POLL* for testing RCU and SRCU
polled grace periods
- add CFcommon.arch for arch-specific Kconfig options
- print number of update types in rcu_torture_write_types()
- add rcutree.nohz_full_patience_delay testing to the TREE07 scenario
- add a stall_cpu_repeat module parameter to test repeated CPU stalls
- add argument to limit number of CPUs a guest OS can use in
torture.sh
rcustall:
- abbreviate RCU CPU stall warnings during CSD-lock stalls
- Allow dump_cpu_task() to be called without disabling preemption
- defer printing stall-warning backtrace when holding rcu_node lock
srcu:
- make SRCU gp seq wrap-around faster
- add KCSAN checks for concurrent updates to ->srcu_n_exp_nodelay and
->reschedule_count which are used in heuristics governing
auto-expediting of normal SRCU grace periods and
grace-period-state-machine delays
- mark idle SRCU-barrier callbacks to help identify stuck
SRCU-barrier callback
rcu tasks:
- remove RCU Tasks Rude asynchronous APIs as they are no longer used
- stop testing RCU Tasks Rude asynchronous APIs
- fix access to non-existent percpu regions
- check processor-ID assumptions during chosen CPU calculation for
callback enqueuing
- update description of rtp->tasks_gp_seq grace-period sequence
number
- add rcu_barrier_cb_is_done() to identify whether a given
rcu_barrier callback is stuck
- mark idle Tasks-RCU-barrier callbacks
- add *torture_stats_print() functions to print detailed diagnostics
for Tasks-RCU variants
- capture start time of rcu_barrier_tasks*() operation to help
distinguish a hung barrier operation from a long series of barrier
operations
refscale:
- add a TINY scenario to support tests of Tiny RCU and Tiny
SRCU
- optimize process_durations() operation
rcuscale:
- dump stacks of stalled rcu_scale_writer() instances and
grace-period statistics when rcu_scale_writer() stalls
- mark idle RCU-barrier callbacks to identify stuck RCU-barrier
callbacks
- print detailed grace-period and barrier diagnostics on
rcu_scale_writer() hangs for Tasks-RCU variants
- warn if async module parameter is specified for RCU implementations
that do not have async primitives such as RCU Tasks Rude
- make all writer tasks report upon hang
- tolerate repeated GFP_KERNEL failure in rcu_scale_writer()
- use special allocator for rcu_scale_writer()
- NULL out top-level pointers to heap memory to avoid double-free
bugs on modprobe failures
- maintain per-task instead of per-CPU callbacks count to avoid any
issues with migration of either tasks or callbacks
- constify struct ref_scale_ops
Fixes:
- use system_unbound_wq for kfree_rcu work to avoid disturbing
isolated CPUs
Misc:
- warn on unexpected rcu_state.srs_done_tail state
- better define "atomic" for list_replace_rcu() and
hlist_replace_rcu() routines
- annotate struct kvfree_rcu_bulk_data with __counted_by()"
* tag 'rcu.release.v6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (90 commits)
rcu: Defer printing stall-warning backtrace when holding rcu_node lock
rcu/nocb: Remove superfluous memory barrier after bypass enqueue
rcu/nocb: Conditionally wake up rcuo if not already waiting on GP
rcu/nocb: Fix RT throttling hrtimer armed from offline CPU
rcu/nocb: Simplify (de-)offloading state machine
context_tracking: Tag context_tracking_enabled_this_cpu() __always_inline
context_tracking, rcu: Rename rcu_dyntick trace event into rcu_watching
rcu: Update stray documentation references to rcu_dynticks_eqs_{enter, exit}()
rcu: Rename rcu_momentary_dyntick_idle() into rcu_momentary_eqs()
rcu: Rename rcu_implicit_dynticks_qs() into rcu_watching_snap_recheck()
rcu: Rename dyntick_save_progress_counter() into rcu_watching_snap_save()
rcu: Rename struct rcu_data .exp_dynticks_snap into .exp_watching_snap
rcu: Rename struct rcu_data .dynticks_snap into .watching_snap
rcu: Rename rcu_dynticks_zero_in_eqs() into rcu_watching_zero_in_eqs()
rcu: Rename rcu_dynticks_in_eqs_since() into rcu_watching_snap_stopped_since()
rcu: Rename rcu_dynticks_in_eqs() into rcu_watching_snap_in_eqs()
rcu: Rename rcu_dynticks_eqs_online() into rcu_watching_online()
context_tracking, rcu: Rename rcu_dynticks_curr_cpu_in_eqs() into rcu_is_watching_curr_cpu()
context_tracking, rcu: Rename rcu_dynticks_task*() into rcu_task*()
refscale: Constify struct ref_scale_ops
...
To fix some critical section races, the interface_lock was added to a few
locations. One of those locations was above where the interface_lock was
declared, so the declaration was moved up before that usage.
Unfortunately, where it was placed was inside a CONFIG_TIMERLAT_TRACER
ifdef block. As the interface_lock is used outside that config, this broke
the build when CONFIG_OSNOISE_TRACER was enabled but
CONFIG_TIMERLAT_TRACER was not.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Helena Anna" <helena.anna.dubel@intel.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Cc: Tomas Glozar <tglozar@redhat.com>
Link: https://lore.kernel.org/20240909103231.23a289e2@gandalf.local.home
Fixes: e6a53481da ("tracing/timerlat: Only clear timer if a kthread exists")
Reported-by: "Bityutskiy, Artem" <artem.bityutskiy@intel.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The timerlat interface will get and put the task that is part of the
"kthread" field of the osn_var to keep it around until all references are
released. But here's a race in the "stop_kthread()" code that will call
put_task_struct() on the kthread if it is not a kernel thread. This can
race with the releasing of the references to that task struct and the
put_task_struct() can be called twice when it should have been called just
once.
Take the interface_lock() in stop_kthread() to synchronize this change.
But to do so, the function stop_per_cpu_kthreads() needs to change the
loop from for_each_online_cpu() to for_each_possible_cpu() and remove the
cpu_read_lock(), as the interface_lock can not be taken while the cpu
locks are held. The only side effect of this change is that it may do some
extra work, as the per_cpu variables of the offline CPUs would not be set
anyway, and would simply be skipped in the loop.
Remove unneeded "return;" in stop_kthread().
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Tomas Glozar <tglozar@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Link: https://lore.kernel.org/20240905113359.2b934242@gandalf.local.home
Fixes: e88ed227f6 ("tracing/timerlat: Add user-space interface")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The timerlat tracer can use user space threads to check for osnoise and
timer latency. If the program using this is killed via a SIGTERM, the
threads are shutdown one at a time and another tracing instance can start
up resetting the threads before they are fully closed. That causes the
hrtimer assigned to the kthread to be shutdown and freed twice when the
dying thread finally closes the file descriptors, causing a use-after-free
bug.
Only cancel the hrtimer if the associated thread is still around. Also add
the interface_lock around the resetting of the tlat_var->kthread.
Note, this is just a quick fix that can be backported to stable. A real
fix is to have a better synchronization between the shutdown of old
threads and the starting of new ones.
Link: https://lore.kernel.org/all/20240820130001.124768-1-tglozar@redhat.com/
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Link: https://lore.kernel.org/20240905085330.45985730@gandalf.local.home
Fixes: e88ed227f6 ("tracing/timerlat: Add user-space interface")
Reported-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The start_kthread() and stop_thread() code was not always called with the
interface_lock held. This means that the kthread variable could be
unexpectedly changed causing the kthread_stop() to be called on it when it
should not have been, leading to:
while true; do
rtla timerlat top -u -q & PID=$!;
sleep 5;
kill -INT $PID;
sleep 0.001;
kill -TERM $PID;
wait $PID;
done
Causing the following OOPS:
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 5 UID: 0 PID: 885 Comm: timerlatu/5 Not tainted 6.11.0-rc4-test-00002-gbc754cc76d1b-dirty #125 a533010b71dab205ad2f507188ce8c82203b0254
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:hrtimer_active+0x58/0x300
Code: 48 c1 ee 03 41 54 48 01 d1 48 01 d6 55 53 48 83 ec 20 80 39 00 0f 85 30 02 00 00 49 8b 6f 30 4c 8d 75 10 4c 89 f0 48 c1 e8 03 <0f> b6 3c 10 4c 89 f0 83 e0 07 83 c0 03 40 38 f8 7c 09 40 84 ff 0f
RSP: 0018:ffff88811d97f940 EFLAGS: 00010202
RAX: 0000000000000002 RBX: ffff88823c6b5b28 RCX: ffffed10478d6b6b
RDX: dffffc0000000000 RSI: ffffed10478d6b6c RDI: ffff88823c6b5b28
RBP: 0000000000000000 R08: ffff88823c6b5b58 R09: ffff88823c6b5b60
R10: ffff88811d97f957 R11: 0000000000000010 R12: 00000000000a801d
R13: ffff88810d8b35d8 R14: 0000000000000010 R15: ffff88823c6b5b28
FS: 0000000000000000(0000) GS:ffff88823c680000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000561858ad7258 CR3: 000000007729e001 CR4: 0000000000170ef0
Call Trace:
<TASK>
? die_addr+0x40/0xa0
? exc_general_protection+0x154/0x230
? asm_exc_general_protection+0x26/0x30
? hrtimer_active+0x58/0x300
? __pfx_mutex_lock+0x10/0x10
? __pfx_locks_remove_file+0x10/0x10
hrtimer_cancel+0x15/0x40
timerlat_fd_release+0x8e/0x1f0
? security_file_release+0x43/0x80
__fput+0x372/0xb10
task_work_run+0x11e/0x1f0
? _raw_spin_lock+0x85/0xe0
? __pfx_task_work_run+0x10/0x10
? poison_slab_object+0x109/0x170
? do_exit+0x7a0/0x24b0
do_exit+0x7bd/0x24b0
? __pfx_migrate_enable+0x10/0x10
? __pfx_do_exit+0x10/0x10
? __pfx_read_tsc+0x10/0x10
? ktime_get+0x64/0x140
? _raw_spin_lock_irq+0x86/0xe0
do_group_exit+0xb0/0x220
get_signal+0x17ba/0x1b50
? vfs_read+0x179/0xa40
? timerlat_fd_read+0x30b/0x9d0
? __pfx_get_signal+0x10/0x10
? __pfx_timerlat_fd_read+0x10/0x10
arch_do_signal_or_restart+0x8c/0x570
? __pfx_arch_do_signal_or_restart+0x10/0x10
? vfs_read+0x179/0xa40
? ksys_read+0xfe/0x1d0
? __pfx_ksys_read+0x10/0x10
syscall_exit_to_user_mode+0xbc/0x130
do_syscall_64+0x74/0x110
? __pfx___rseq_handle_notify_resume+0x10/0x10
? __pfx_ksys_read+0x10/0x10
? fpregs_restore_userregs+0xdb/0x1e0
? fpregs_restore_userregs+0xdb/0x1e0
? syscall_exit_to_user_mode+0x116/0x130
? do_syscall_64+0x74/0x110
? do_syscall_64+0x74/0x110
? do_syscall_64+0x74/0x110
entry_SYSCALL_64_after_hwframe+0x71/0x79
RIP: 0033:0x7ff0070eca9c
Code: Unable to access opcode bytes at 0x7ff0070eca72.
RSP: 002b:00007ff006dff8c0 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: 0000000000000000 RBX: 0000000000000005 RCX: 00007ff0070eca9c
RDX: 0000000000000400 RSI: 00007ff006dff9a0 RDI: 0000000000000003
RBP: 00007ff006dffde0 R08: 0000000000000000 R09: 00007ff000000ba0
R10: 00007ff007004b08 R11: 0000000000000246 R12: 0000000000000003
R13: 00007ff006dff9a0 R14: 0000000000000007 R15: 0000000000000008
</TASK>
Modules linked in: snd_hda_intel snd_intel_dspcfg snd_intel_sdw_acpi snd_hda_codec snd_hwdep snd_hda_core
---[ end trace 0000000000000000 ]---
This is because it would mistakenly call kthread_stop() on a user space
thread making it "exit" before it actually exits.
Since kthreads are created based on global behavior, use a cpumask to know
when kthreads are running and that they need to be shutdown before
proceeding to do new work.
Link: https://lore.kernel.org/all/20240820130001.124768-1-tglozar@redhat.com/
This was debugged by using the persistent ring buffer:
Link: https://lore.kernel.org/all/20240823013902.135036960@goodmis.org/
Note, locking was originally used to fix this, but that proved to cause too
many deadlocks to work around:
https://lore.kernel.org/linux-trace-kernel/20240823102816.5e55753b@gandalf.local.home/
Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: "Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Link: https://lore.kernel.org/20240904103428.08efdf4c@gandalf.local.home
Fixes: e88ed227f6 ("tracing/timerlat: Add user-space interface")
Reported-by: Tomas Glozar <tglozar@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, replace "dyntick_idle" into "eqs" to drop the dyntick
reference.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Change the default threshold for osnoise to 1us, so that any noise
equal or above this value is recorded. Let the user set a higher
threshold if necessary.
Link: https://lore.kernel.org/linux-trace-kernel/Zmb-QhiiiI6jM9To@uudg.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Suggested-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Reviewed-by: Clark Williams <williams@redhat.com>
Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@redhat.com>
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Going a step further, we propose a way to use any user-space
workload as the task waiting for the timerlat timer. This is done
via a per-CPU file named osnoise/cpu$id/timerlat_fd file.
The tracef_fd allows a task to open at a time. When a task reads
the file, the timerlat timer is armed for future osnoise/timerlat_period_us
time. When the timer fires, it prints the IRQ latency and
wakes up the user-space thread waiting in the timerlat_fd.
The thread then starts to run, executes the timerlat measurement, prints
the thread scheduling latency and returns to user-space.
When the thread rereads the timerlat_fd, the tracer will print the
user-ret(urn) latency, which is an additional metric.
This additional metric is also traced by the tracer and can be used, for
example of measuring the context switch overhead from kernel-to-user and
user-to-kernel, or the response time for an arbitrary execution in
user-space.
The tracer supports one thread per CPU, the thread must be pinned to
the CPU, and it cannot migrate while holding the timerlat_fd. The reason
is that the tracer is per CPU (nothing prohibits the tracer from
allowing migrations in the future). The tracer monitors the migration
of the thread and disables the tracer if detected.
The timerlat_fd is only available for opening/reading when timerlat
tracer is enabled, and NO_OSNOISE_WORKLOAD is set.
The simplest way to activate this feature from user-space is:
-------------------------------- %< -----------------------------------
int main(void)
{
char buffer[1024];
int timerlat_fd;
int retval;
long cpu = 0; /* place in CPU 0 */
cpu_set_t set;
CPU_ZERO(&set);
CPU_SET(cpu, &set);
if (sched_setaffinity(gettid(), sizeof(set), &set) == -1)
return 1;
snprintf(buffer, sizeof(buffer),
"/sys/kernel/tracing/osnoise/per_cpu/cpu%ld/timerlat_fd",
cpu);
timerlat_fd = open(buffer, O_RDONLY);
if (timerlat_fd < 0) {
printf("error opening %s: %s\n", buffer, strerror(errno));
exit(1);
}
for (;;) {
retval = read(timerlat_fd, buffer, 1024);
if (retval < 0)
break;
}
close(timerlat_fd);
exit(0);
}
-------------------------------- >% -----------------------------------
When disabling timerlat, if there is a workload holding the timerlat_fd,
the SIGKILL will be sent to the thread.
Link: https://lkml.kernel.org/r/69fe66a863d2792ff4c3a149bf9e32e26468bb3a.1686063934.git.bristot@kernel.org
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: William White <chwhite@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
In the case of all tracing instances being off, sleep for the entire
period.
Q: Why not kill all threads so?
A: It is valid and useful to start the threads with tracing off.
For example, rtla disables tracing, starts the tracer, applies the
scheduling setup to the threads, e.g., sched priority and cgroup,
and then begin tracing with all set.
Skipping the period helps to speed up rtla setup and save the
trace after a stop tracing.
Link: https://lkml.kernel.org/r/aa4dd9b7e76fcb63901fe5407e15ec002b318599.1686063934.git.bristot@kernel.org
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: William White <chwhite@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Currently, osnoise/timerlat threads run with PF_NO_SETAFFINITY set.
It works well, however, cgroups do not allow PF_NO_SETAFFINITY threads
to be accepted, and this creates a limitation to osnoise/timerlat.
To avoid this limitation, disable migration of the threads as soon
as they start to run, and then clean the PF_NO_SETAFFINITY flag (still)
used during thread creation.
If for some reason a thread migration is requested, e.g., via
sched_settafinity, the tracer thread will notice and exit.
Link: https://lkml.kernel.org/r/8ba8bc9c15b3ea40cf73cf67a9bc061a264609f0.1686063934.git.bristot@kernel.org
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: William White <chwhite@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
While testing rtla timerlat auto analysis, I reach a condition where
the interface was not receiving tracing data. I was able to manually
reproduce the problem with these steps:
# echo 0 > tracing_on # disable trace
# echo 1 > osnoise/stop_tracing_us # stop trace if timerlat irq > 1 us
# echo timerlat > current_tracer # enable timerlat tracer
# sleep 1 # wait... that is the time when rtla
# apply configs like prio or cgroup
# echo 1 > tracing_on # start tracing
# cat trace
# tracer: timerlat
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / _-=> migrate-disable
# |||| / delay
# ||||| ACTIVATION
# TASK-PID CPU# ||||| TIMESTAMP ID CONTEXT LATENCY
# | | | ||||| | | | |
NOTHING!
Then, trying to enable tracing again with echo 1 > tracing_on resulted
in no change: the trace was still not tracing.
This problem happens because the timerlat IRQ hits the stop tracing
condition while tracing is off, and do not wake up the timerlat thread,
so the timerlat threads are kept sleeping forever, resulting in no
trace, even after re-enabling the tracer.
Avoid this condition by always waking up the threads, even after stopping
tracing, allowing the tracer to return to its normal operating after
a new tracing on.
Link: https://lore.kernel.org/linux-trace-kernel/1ed8f830638b20a39d535d27d908e319a9a3c4e2.1683822622.git.bristot@kernel.org
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: stable@vger.kernel.org
Fixes: a955d7eac1 ("trace: Add timerlat tracer")
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
o MAINTAINERS files additions and changes.
o Fix hotplug warning in nohz code.
o Tick dependency changes by Zqiang.
o Lazy-RCU shrinker fixes by Zqiang.
o rcu-tasks stall reporting improvements by Neeraj.
o Initial changes for renaming of k[v]free_rcu() to its new k[v]free_rcu_mightsleep()
name for robustness.
o Documentation Updates:
o Significant changes to srcu_struct size.
o Deadlock detection for srcu_read_lock() vs synchronize_srcu() from Boqun.
o rcutorture and rcu-related tool, which are targeted for v6.4 from Boqun's tree.
o Other misc changes.
-----BEGIN PGP SIGNATURE-----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=Rgbj
-----END PGP SIGNATURE-----
Merge tag 'rcu.6.4.april5.2023.3' of git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux
Pull RCU updates from Joel Fernandes:
- Updates and additions to MAINTAINERS files, with Boqun being added to
the RCU entry and Zqiang being added as an RCU reviewer.
I have also transitioned from reviewer to maintainer; however, Paul
will be taking over sending RCU pull-requests for the next merge
window.
- Resolution of hotplug warning in nohz code, achieved by fixing
cpu_is_hotpluggable() through interaction with the nohz subsystem.
Tick dependency modifications by Zqiang, focusing on fixing usage of
the TICK_DEP_BIT_RCU_EXP bitmask.
- Avoid needless calls to the rcu-lazy shrinker for CONFIG_RCU_LAZY=n
kernels, fixed by Zqiang.
- Improvements to rcu-tasks stall reporting by Neeraj.
- Initial renaming of k[v]free_rcu() to k[v]free_rcu_mightsleep() for
increased robustness, affecting several components like mac802154,
drbd, vmw_vmci, tracing, and more.
A report by Eric Dumazet showed that the API could be unknowingly
used in an atomic context, so we'd rather make sure they know what
they're asking for by being explicit:
https://lore.kernel.org/all/20221202052847.2623997-1-edumazet@google.com/
- Documentation updates, including corrections to spelling,
clarifications in comments, and improvements to the srcu_size_state
comments.
- Better srcu_struct cache locality for readers, by adjusting the size
of srcu_struct in support of SRCU usage by Christoph Hellwig.
- Teach lockdep to detect deadlocks between srcu_read_lock() vs
synchronize_srcu() contributed by Boqun.
Previously lockdep could not detect such deadlocks, now it can.
- Integration of rcutorture and rcu-related tools, targeted for v6.4
from Boqun's tree, featuring new SRCU deadlock scenarios, test_nmis
module parameter, and more
- Miscellaneous changes, various code cleanups and comment improvements
* tag 'rcu.6.4.april5.2023.3' of git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux: (71 commits)
checkpatch: Error out if deprecated RCU API used
mac802154: Rename kfree_rcu() to kvfree_rcu_mightsleep()
rcuscale: Rename kfree_rcu() to kfree_rcu_mightsleep()
ext4/super: Rename kfree_rcu() to kfree_rcu_mightsleep()
net/mlx5: Rename kfree_rcu() to kfree_rcu_mightsleep()
net/sysctl: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
lib/test_vmalloc.c: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
tracing: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
misc: vmw_vmci: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
drbd: Rename kvfree_rcu() to kvfree_rcu_mightsleep()
rcu: Protect rcu_print_task_exp_stall() ->exp_tasks access
rcu: Avoid stack overflow due to __rcu_irq_enter_check_tick() being kprobe-ed
rcu-tasks: Report stalls during synchronize_srcu() in rcu_tasks_postscan()
rcu: Permit start_poll_synchronize_rcu_expedited() to be invoked early
rcu: Remove never-set needwake assignment from rcu_report_qs_rdp()
rcu: Register rcu-lazy shrinker only for CONFIG_RCU_LAZY=y kernels
rcu: Fix missing TICK_DEP_MASK_RCU_EXP dependency check
rcu: Fix set/clear TICK_DEP_BIT_RCU_EXP bitmask race
rcu/trace: use strscpy() to instead of strncpy()
tick/nohz: Fix cpu_is_hotpluggable() by checking with nohz subsystem
...
The kvfree_rcu() macro's single-argument form is deprecated. Therefore
switch to the new kvfree_rcu_mightsleep() variant. The goal is to
avoid accidental use of the single-argument forms, which can introduce
functionality bugs in atomic contexts and latency bugs in non-atomic
contexts.
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
osnoise/timerlat tracers are reporting new max latency on instances
where the tracing is off, creating inconsistencies between the max
reported values in the trace and in the tracing_max_latency. Thus
only report new tracing_max_latency on active tracing instances.
Link: https://lkml.kernel.org/r/ecd109fde4a0c24ab0f00ba1e9a144ac19a91322.1680104184.git.bristot@kernel.org
Cc: stable@vger.kernel.org
Fixes: dae181349f ("tracing/osnoise: Support a list of trace_array *tr")
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
timerlat is not reporting a new tracing_max_latency for the thread
latency. The reason is that it is not calling notify_new_max_latency()
function after the new thread latency is sampled.
Call notify_new_max_latency() after computing the thread latency.
Link: https://lkml.kernel.org/r/16e18d61d69073d0192ace07bf61e405cca96e9c.1680104184.git.bristot@kernel.org
Cc: stable@vger.kernel.org
Fixes: dae181349f ("tracing/osnoise: Support a list of trace_array *tr")
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
smatch reports several similar warnings
kernel/trace/trace_osnoise.c:220:1: warning:
symbol '__pcpu_scope_per_cpu_osnoise_var' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:243:1: warning:
symbol '__pcpu_scope_per_cpu_timerlat_var' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:335:14: warning:
symbol 'interface_lock' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:2242:5: warning:
symbol 'timerlat_min_period' was not declared. Should it be static?
kernel/trace/trace_osnoise.c:2243:5: warning:
symbol 'timerlat_max_period' was not declared. Should it be static?
These variables are only used in trace_osnoise.c, so it should be static
Link: https://lore.kernel.org/linux-trace-kernel/20230309150414.4036764-1-trix@redhat.com
Signed-off-by: Tom Rix <trix@redhat.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
list_for_each_entry_rcu() has built-in RCU and lock checking.
Pass cond argument to list_for_each_entry_rcu() to silence false lockdep
warning when CONFIG_PROVE_RCU_LIST is enabled.
Execute as follow:
[tracing]# echo osnoise > current_tracer
[tracing]# echo 1 > tracing_on
[tracing]# echo 0 > tracing_on
The trace_types_lock is held when osnoise_tracer_stop() or
timerlat_tracer_stop() are called in the non-RCU read side section.
So, pass lockdep_is_held(&trace_types_lock) to silence false lockdep
warning.
Link: https://lkml.kernel.org/r/20221227023036.784337-1-nashuiliang@gmail.com
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: dae181349f ("tracing/osnoise: Support a list of trace_array *tr")
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The osnoise workload runs with preemption and IRQs enabled in such
a way as to allow all sorts of noise to disturb osnoise's execution.
hwlat tracer has a similar workload but works with irq disabled,
allowing only NMIs and the hardware to generate noise.
While thinking about adding an options file to hwlat tracer to
allow the system to panic, and other features I was thinking
to add, like having a tracepoint at each noise detection, it
came to my mind that is easier to make osnoise and also do
hardware latency detection than making hwlat "feature compatible"
with osnoise.
Other points are:
- osnoise already has an independent cpu file.
- osnoise has a more intuitive interface, e.g., runtime/period vs.
window/width (and people often need help remembering what it is).
- osnoise: tracepoints
- osnoise stop options
- osnoise options file itself
Moreover, the user-space side (in rtla) is simplified by reusing the
existing osnoise code.
Finally, people have been asking me about using osnoise for hw latency
detection, and I have to explain that it was sufficient but not
necessary. These options make it sufficient and necessary.
Adding a Suggested-by Clark, as he often asked me about this
possibility.
Link: https://lkml.kernel.org/r/d9c6c19135497054986900f94c8e47410b15316a.1670623111.git.bristot@kernel.org
Cc: Suggested-by: Clark Williams <williams@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Often the latency observed in a CPU is not caused by the work being done
in the CPU itself, but by work done on another CPU that causes the
hardware to stall all CPUs. In this case, it is interesting to know
what is happening on ALL CPUs, and the best way to do this is via
crash dump analysis.
Add the PANIC_ON_STOP option to osnoise/timerlat tracers. The default
behavior is having this option off. When enabled by the user, the system
will panic after hitting a stop tracing condition.
This option was motivated by a real scenario that Juri Lelli and I
were debugging.
Link: https://lkml.kernel.org/r/249ce4287c6725543e6db845a6e0df621dc67db5.1670623111.git.bristot@kernel.org
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Bagas Sanjaya <bagasdotme@gmail.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Make osnoise_options static, as reported by the kernel test robot.
Link: https://lkml.kernel.org/r/63255826485400d7a2270e9c5e66111079671e7a.1670228712.git.bristot@kernel.org
Reported-by: kernel test robot <lkp@intel.com>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Add the tracing/osnoise/options file to control
osnoise/timerlat tracer features. It is a single
file to contain multiple features, similar to
the sched/features file.
Reading the file displays a list of options. Writing
the OPTION_NAME enables it, writing NO_OPTION_NAME disables
it.
The DEAFULTS is a particular option that resets the options
to the default ones.
It uses a bitmask to keep track of the status of the option. When
needed, we can add a list of static keys, but for now
it does not justify the memory increase.
Link: https://lkml.kernel.org/r/f8d34aefdb225d2603fcb4c02a120832a0cd3339.1668692096.git.bristot@kernel.org
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The duration type is a 64 long value, not an int. This was
causing some long noise to report wrong values.
Change the duration to a 64 bits value.
Link: https://lkml.kernel.org/r/a93d8a8378c7973e9c609de05826533c9e977939.1668692096.git.bristot@kernel.org
Cc: stable@vger.kernel.org
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Fixes: bce29ac9ce ("trace: Add osnoise tracer")
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
There is a recursive lock on the cpu_hotplug_lock.
In kernel/trace/trace_osnoise.c:<start/stop>_per_cpu_kthreads:
- start_per_cpu_kthreads calls cpus_read_lock() and if
start_kthreads returns a error it will call stop_per_cpu_kthreads.
- stop_per_cpu_kthreads then calls cpus_read_lock() again causing
deadlock.
Fix this by calling cpus_read_unlock() before calling
stop_per_cpu_kthreads. This behavior can also be seen in commit
f46b16520a ("trace/hwlat: Implement the per-cpu mode").
This error was noticed during the LTP ftrace-stress-test:
WARNING: possible recursive locking detected
--------------------------------------------
sh/275006 is trying to acquire lock:
ffffffffb02f5400 (cpu_hotplug_lock){++++}-{0:0}, at: stop_per_cpu_kthreads
but task is already holding lock:
ffffffffb02f5400 (cpu_hotplug_lock){++++}-{0:0}, at: start_per_cpu_kthreads
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(cpu_hotplug_lock);
lock(cpu_hotplug_lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
3 locks held by sh/275006:
#0: ffff8881023f0470 (sb_writers#24){.+.+}-{0:0}, at: ksys_write
#1: ffffffffb084f430 (trace_types_lock){+.+.}-{3:3}, at: rb_simple_write
#2: ffffffffb02f5400 (cpu_hotplug_lock){++++}-{0:0}, at: start_per_cpu_kthreads
Link: https://lkml.kernel.org/r/20220919144932.3064014-1-npache@redhat.com
Fixes: c8895e271f ("trace/osnoise: Support hotplug operations")
Signed-off-by: Nico Pache <npache@redhat.com>
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
- The majority of the changes are for fixes and clean ups.
Noticeable changes:
- Rework trace event triggers code to be easier to interact with.
- Support for embedding bootconfig with the kernel (as suppose to having it
embedded in initram). This is useful for embedded boards without initram
disks.
- Speed up boot by parallelizing the creation of tracefs files.
- Allow absolute ring buffer timestamps handle timestamps that use more than
59 bits.
- Added new tracing clock "TAI" (International Atomic Time)
- Have weak functions show up in available_filter_function list as:
__ftrace_invalid_address___<invalid-offset>
instead of using the name of the function before it.
-----BEGIN PGP SIGNATURE-----
iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCYpOgXRQccm9zdGVkdEBn
b29kbWlzLm9yZwAKCRAp5XQQmuv6qjkKAQDbpemxvpFyJlZqT8KgEIXubu+ag2/q
p0XDHaPS0zF9OQEAjTxg6GMEbnFYl6fzxZtOoEbiaQ7ppfdhRI8t6sSMVA8=
=+nDD
-----END PGP SIGNATURE-----
Merge tag 'trace-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing updates from Steven Rostedt:
"The majority of the changes are for fixes and clean ups.
Notable changes:
- Rework trace event triggers code to be easier to interact with.
- Support for embedding bootconfig with the kernel (as suppose to
having it embedded in initram). This is useful for embedded boards
without initram disks.
- Speed up boot by parallelizing the creation of tracefs files.
- Allow absolute ring buffer timestamps handle timestamps that use
more than 59 bits.
- Added new tracing clock "TAI" (International Atomic Time)
- Have weak functions show up in available_filter_function list as:
__ftrace_invalid_address___<invalid-offset> instead of using the
name of the function before it"
* tag 'trace-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (52 commits)
ftrace: Add FTRACE_MCOUNT_MAX_OFFSET to avoid adding weak function
tracing: Fix comments for event_trigger_separate_filter()
x86/traceponit: Fix comment about irq vector tracepoints
x86,tracing: Remove unused headers
ftrace: Clean up hash direct_functions on register failures
tracing: Fix comments of create_filter()
tracing: Disable kcov on trace_preemptirq.c
tracing: Initialize integer variable to prevent garbage return value
ftrace: Fix typo in comment
ftrace: Remove return value of ftrace_arch_modify_*()
tracing: Cleanup code by removing init "char *name"
tracing: Change "char *" string form to "char []"
tracing/timerlat: Do not wakeup the thread if the trace stops at the IRQ
tracing/timerlat: Print stacktrace in the IRQ handler if needed
tracing/timerlat: Notify IRQ new max latency only if stop tracing is set
kprobes: Fix build errors with CONFIG_KRETPROBES=n
tracing: Fix return value of trace_pid_write()
tracing: Fix potential double free in create_var_ref()
tracing: Use strim() to remove whitespace instead of doing it manually
ftrace: Deal with error return code of the ftrace_process_locs() function
...
There is no need to wakeup the timerlat/ thread if stop tracing is hit
at the timerlat's IRQ handler.
Return before waking up timerlat's thread.
Link: https://lkml.kernel.org/r/b392356c91b56aedd2b289513cc56a84cf87e60d.1652175637.git.bristot@kernel.org
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
If print_stack and stop_tracing_us are set, and stop_tracing_us is hit
with latency higher than or equal to print_stack, print the
stack at the IRQ handler as it is useful to define the root cause for
the IRQ latency.
Link: https://lkml.kernel.org/r/fd04530ce98ae9270e41bb124ee5bf67b05ecfed.1652175637.git.bristot@kernel.org
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Currently, the notification of a new max latency is sent from
timerlat's IRQ handler anytime a new max latency is found.
While this behavior is not wrong, the send IPI overhead itself
will increase the thread latency and that is not the desired
effect (tracing overhead).
Moreover, the thread will notify a new max latency again because
the thread latency as it is always higher than the IRQ latency
that woke it up.
The only case in which it is helpful to notify a new max latency
from IRQ is when stop tracing (for the IRQ) is set, as in this
case, the thread will not be dispatched.
Notify a new max latency from the IRQ handler only if stop tracing is
set for the IRQ handler.
Link: https://lkml.kernel.org/r/2c2d9a56c0886c8402ba320de32856cbbb10c2bb.1652175637.git.bristot@kernel.org
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Ingo Molnar <mingo@redhat.com>
Reported-by: Clark Williams <williams@redhat.com>
Fixes: a955d7eac1 ("trace: Add timerlat tracer")
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Commit fa2c3254d7 (sched/tracing: Don't re-read p->state when emitting
sched_switch event, 2022-01-20) added a new prev_state argument to the
sched_switch tracepoint, before the prev task_struct pointer.
This reordering of arguments broke BPF programs that use the raw
tracepoint (e.g. tp_btf programs). The type of the second argument has
changed and existing programs that assume a task_struct* argument
(e.g. for bpf_task_storage access) will now fail to verify.
If we instead append the new argument to the end, all existing programs
would continue to work and can conditionally extract the prev_state
argument on supported kernel versions.
Fixes: fa2c3254d7 (sched/tracing: Don't re-read p->state when emitting sched_switch event, 2022-01-20)
Signed-off-by: Delyan Kratunov <delyank@fb.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lkml.kernel.org/r/c8a6930dfdd58a4a5755fc01732675472979732b.camel@fb.com
At the moment running osnoise on a nohz_full CPU or uncontested FIFO
priority and a PREEMPT_RCU kernel might have the side effect of
extending grace periods too much. This will entice RCU to force a
context switch on the wayward CPU to end the grace period, all while
introducing unwarranted noise into the tracer. This behaviour is
unavoidable as overly extending grace periods might exhaust the system's
memory.
This same exact problem is what extended quiescent states (EQS) were
created for, conversely, rcu_momentary_dyntick_idle() emulates them by
performing a zero duration EQS. So let's make use of it.
In the common case rcu_momentary_dyntick_idle() is fairly inexpensive:
atomically incrementing a local per-CPU counter and doing a store. So it
shouldn't affect osnoise's measurements (which has a 1us granularity),
so we'll call it unanimously.
The uncommon case involve calling rcu_momentary_dyntick_idle() after
having the osnoise process:
- Receive an expedited quiescent state IPI with preemption disabled or
during an RCU critical section. (activates rdp->cpu_no_qs.b.exp
code-path).
- Being preempted within in an RCU critical section and having the
subsequent outermost rcu_read_unlock() called with interrupts
disabled. (t->rcu_read_unlock_special.b.blocked code-path).
Neither of those are possible at the moment, and are unlikely to be in
the future given the osnoise's loop design. On top of this, the noise
generated by the situations described above is unavoidable, and if not
exposed by rcu_momentary_dyntick_idle() will be eventually seen in
subsequent rcu_read_unlock() calls or schedule operations.
Link: https://lkml.kernel.org/r/20220307180740.577607-1-nsaenzju@redhat.com
Cc: stable@vger.kernel.org
Fixes: bce29ac9ce ("trace: Add osnoise tracer")
Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Nicolas reported that using:
# trace-cmd record -e all -M 10 -p osnoise --poll
Resulted in the following kernel warning:
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1217 at kernel/tracepoint.c:404 tracepoint_probe_unregister+0x280/0x370
[...]
CPU: 0 PID: 1217 Comm: trace-cmd Not tainted 5.17.0-rc6-next-20220307-nico+ #19
RIP: 0010:tracepoint_probe_unregister+0x280/0x370
[...]
CR2: 00007ff919b29497 CR3: 0000000109da4005 CR4: 0000000000170ef0
Call Trace:
<TASK>
osnoise_workload_stop+0x36/0x90
tracing_set_tracer+0x108/0x260
tracing_set_trace_write+0x94/0xd0
? __check_object_size.part.0+0x10a/0x150
? selinux_file_permission+0x104/0x150
vfs_write+0xb5/0x290
ksys_write+0x5f/0xe0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7ff919a18127
[...]
---[ end trace 0000000000000000 ]---
The warning complains about an attempt to unregister an
unregistered tracepoint.
This happens on trace-cmd because it first stops tracing, and
then switches the tracer to nop. Which is equivalent to:
# cd /sys/kernel/tracing/
# echo osnoise > current_tracer
# echo 0 > tracing_on
# echo nop > current_tracer
The osnoise tracer stops the workload when no trace instance
is actually collecting data. This can be caused both by
disabling tracing or disabling the tracer itself.
To avoid unregistering events twice, use the existing
trace_osnoise_callback_enabled variable to check if the events
(and the workload) are actually active before trying to
deactivate them.
Link: https://lore.kernel.org/all/c898d1911f7f9303b7e14726e7cc9678fbfb4a0e.camel@redhat.com/
Link: https://lkml.kernel.org/r/938765e17d5a781c2df429a98f0b2e7cc317b022.1646823913.git.bristot@kernel.org
Cc: stable@vger.kernel.org
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Fixes: 2fac8d6486 ("tracing/osnoise: Allow multiple instances of the same tracer")
Reported-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
As of commit
c6e7bd7afa ("sched/core: Optimize ttwu() spinning on p->on_cpu")
the following sequence becomes possible:
p->__state = TASK_INTERRUPTIBLE;
__schedule()
deactivate_task(p);
ttwu()
READ !p->on_rq
p->__state=TASK_WAKING
trace_sched_switch()
__trace_sched_switch_state()
task_state_index()
return 0;
TASK_WAKING isn't in TASK_REPORT, so the task appears as TASK_RUNNING in
the trace event.
Prevent this by pushing the value read from __schedule() down the trace
event.
Reported-by: Abhijeet Dharmapurikar <adharmap@quicinc.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20220120162520.570782-2-valentin.schneider@arm.com
osnoise's runtime and period are in the microseconds scale, but it is
currently sleeping in the millisecond's scale. This behavior roots in the
usage of hwlat as the skeleton for osnoise.
Make osnoise to sleep in the microseconds scale. Also, move the sleep to
a specialized function.
Link: https://lkml.kernel.org/r/302aa6c7bdf2d131719b22901905e9da122a11b2.1645197336.git.bristot@kernel.org
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
New:
- The Real Time Linux Analysis (RTLA) tool is added to the tools directory.
- Can safely filter on user space pointers with: field.ustring ~ "match-string"
- eprobes can now be filtered like any other event.
- trace_marker(_raw) now uses stream_open() to allow multiple threads to safely
write to it. Note, this could possibly break existing user space, but we will
not know until we hear about it, and then can revert the change if need be.
- New field in events to display when bottom halfs are disabled.
- Sorting of the ftrace functions are now done at compile time instead of
at bootup.
Infrastructure changes to support future efforts:
- Added __rel_loc type for trace events. Similar to __data_loc but the offset
to the dynamic data is based off of the location of the descriptor and not
the beginning of the event. Needed for user defined events.
- Some simplification of event trigger code.
- Make synthetic events process its callback better to not hinder other
event callbacks that are registered. Needed for user defined events.
And other small fixes and clean ups.
-
-----BEGIN PGP SIGNATURE-----
iIoEABYIADIWIQRRSw7ePDh/lE+zeZMp5XQQmuv6qgUCYeGvcxQccm9zdGVkdEBn
b29kbWlzLm9yZwAKCRAp5XQQmuv6qrZtAP9ICjJxX54MTErElhhUL/NFLV7wqhJi
OIAgmp6jGVRqPAD+JxQtBnGH+3XMd71ioQkTfQ1rp+jBz2ERBj2DmELUAg0=
=zmda
-----END PGP SIGNATURE-----
Merge tag 'trace-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing updates from Steven Rostedt:
"New:
- The Real Time Linux Analysis (RTLA) tool is added to the tools
directory.
- Can safely filter on user space pointers with: field.ustring ~
"match-string"
- eprobes can now be filtered like any other event.
- trace_marker(_raw) now uses stream_open() to allow multiple threads
to safely write to it. Note, this could possibly break existing
user space, but we will not know until we hear about it, and then
can revert the change if need be.
- New field in events to display when bottom halfs are disabled.
- Sorting of the ftrace functions are now done at compile time
instead of at bootup.
Infrastructure changes to support future efforts:
- Added __rel_loc type for trace events. Similar to __data_loc but
the offset to the dynamic data is based off of the location of the
descriptor and not the beginning of the event. Needed for user
defined events.
- Some simplification of event trigger code.
- Make synthetic events process its callback better to not hinder
other event callbacks that are registered. Needed for user defined
events.
And other small fixes and cleanups"
* tag 'trace-v5.17' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (50 commits)
tracing: Add ustring operation to filtering string pointers
rtla: Add rtla timerlat hist documentation
rtla: Add rtla timerlat top documentation
rtla: Add rtla timerlat documentation
rtla: Add rtla osnoise hist documentation
rtla: Add rtla osnoise top documentation
rtla: Add rtla osnoise man page
rtla: Add Documentation
rtla/timerlat: Add timerlat hist mode
rtla: Add timerlat tool and timelart top mode
rtla/osnoise: Add the hist mode
rtla/osnoise: Add osnoise top mode
rtla: Add osnoise tool
rtla: Helper functions for rtla
rtla: Real-Time Linux Analysis tool
tracing/osnoise: Properly unhook events if start_per_cpu_kthreads() fails
tracing: Remove duplicate warnings when calling trace_create_file()
tracing/kprobes: 'nmissed' not showed correctly for kretprobe
tracing: Add test for user space strings when filtering on string pointers
tracing: Have syscall trace events use trace_event_buffer_lock_reserve()
...
If start_per_cpu_kthreads() called from osnoise_workload_start() returns
error, event hooks are left in broken state: unhook_irq_events() called
but unhook_thread_events() and unhook_softirq_events() not called, and
trace_osnoise_callback_enabled flag not cleared.
On the next tracer enable, hooks get not installed due to
trace_osnoise_callback_enabled flag.
And on the further tracer disable an attempt to remove non-installed
hooks happened, hitting a WARN_ON_ONCE() in tracepoint_remove_func().
Fix the error path by adding the missing part of cleanup.
While at this, introduce osnoise_unhook_events() to avoid code
duplication between this error path and normal tracer disable.
Link: https://lkml.kernel.org/r/20220109153459.3701773-1-nikita.yushchenko@virtuozzo.com
Cc: stable@vger.kernel.org
Fixes: bce29ac9ce ("trace: Add osnoise tracer")
Acked-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Nikita Yushchenko <nikita.yushchenko@virtuozzo.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Instead of invoking a synchronize_rcu() to free a pointer
after a grace period we can directly make use of new API
that does the same but in more efficient way.
Link: https://lkml.kernel.org/r/20211124110308.2053-10-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Remove CONFIG_PREEMPT_RT from inside functions, avoiding
compilation problems in the future.
Link: https://lkml.kernel.org/r/37ee0881b033cdc513efc84ebea26cf77880c8c2.1635702894.git.bristot@kernel.org
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: linux-rt-users@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Remove CONFIG_STACKTRACE from inside functions, avoiding
compilation problems in the future.
Link: https://lkml.kernel.org/r/3465cca2f28e1ba602a1fc8bdb28d12950b5226e.1635702894.git.bristot@kernel.org
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: linux-rt-users@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Currently, the user can start only one instance of timerlat/osnoise
tracers and the tracers cannot run in parallel.
As starting point to add more flexibility, let's allow the same tracer to
run on different trace instances. The workload will start when the first
trace_array (instance) is registered and stop when the last instance
is unregistered.
So, while this patch allows the same tracer to run in multiple
instances (e.g., two instances running osnoise), it still does not allow
instances of timerlat and osnoise in parallel (e.g., one timerlat and
osnoise). That is because the osnoise: events have different behavior
depending on which tracer is enabled (osnoise or timerlat). Enabling
the parallel usage of these two tracers is in my TODO list.
Link: https://lkml.kernel.org/r/38c8f14b613492a4f3f938d9d3bf0b063b72f0f0.1635702894.git.bristot@kernel.org
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: linux-rt-users@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Remove CONFIG_TIMERLAT_TRACER from inside functions, avoiding
compilation problems in the future.
Link: https://lkml.kernel.org/r/8245abb5a112d249f5da6c1df499244ad9e647bc.1635702894.git.bristot@kernel.org
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: linux-rt-users@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
osnoise/timerlat were built to run a single instance, and for this,
a single variable is enough to store the current struct trace_array
*tr with information about the tracing instance. This is done via
the *osnoise_trace variable. A trace_array represents a trace instance.
In preparation to support multiple instances, replace the
*osnoise_trace variable with an RCU protected list of instances.
The operations that refer to an instance now propagate to all
elements of the list (all instances).
Also, replace the osnoise_busy variable with a check if the list
has elements (busy).
No functional change is expected with this patch, i.e., only one
instance is allowed yet.
Link: https://lkml.kernel.org/r/91d006e889b9a5d1ff258fe6077f021ae3f26372.1635702894.git.bristot@kernel.org
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Clark Williams <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: linux-rt-users@vger.kernel.org
Cc: linux-trace-devel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
