Provide functions nbcon_device_try_acquire() and
nbcon_device_release() which will try to acquire the nbcon
console ownership with NBCON_PRIO_NORMAL and mark it unsafe for
handover/takeover.
These functions are to be used together with the device-specific
locking when performing non-printing activities on the console
device. They will allow synchronization against the
atomic_write() callback which will be serialized, for higher
priority contexts, only by acquiring the console context
ownership.
Pitfalls:
The API requires to be called in a context with migration
disabled because it uses per-CPU variables internally.
The context is set unsafe for a takeover all the time. It
guarantees full serialization against any atomic_write() caller
except for the final flush in panic() which might try an unsafe
takeover.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-14-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
Console drivers typically have to deal with access to the
hardware via user input/output (such as an interactive login
shell) and output of kernel messages via printk() calls.
They use some classic driver-specific locking mechanism in most
situations. But console->write_atomic() callbacks, used by nbcon
consoles, are synchronized only by acquiring the console
context.
The synchronization via the console context ownership is possible
only when the console driver is registered. It is when a
particular device driver is connected with a particular console
driver.
The two synchronization mechanisms must be synchronized between
each other. It is tricky because the console context ownership
is quite special. It might be taken over by a higher priority
context. Also CPU migration must be disabled. The most tricky
part is to (dis)connect these two mechanisms during the console
(un)registration.
Use the driver-specific locking callbacks: device_lock(),
device_unlock(). They allow taking the device-specific lock
while the device is being (un)registered by the related console
driver.
For example, these callbacks lock/unlock the port lock for
serial port drivers.
Note that the driver-specific locking is only needed during
(un)register if it is an nbcon console with the write_atomic()
callback implemented. If write_atomic() is not implemented, the
driver should never attempt to access the hardware without
first acquiring its driver-specific lock.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-10-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
The return value of write_atomic() does not provide any useful
information. On the contrary, it makes things more complicated
for the caller to appropriately deal with the information.
Change write_atomic() to not have a return value. If the
message did not get printed due to loss of ownership, the
caller will notice this on its own. If ownership was not lost,
it will be assumed that the driver successfully printed the
message and the sequence number for that console will be
incremented.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-7-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
The functions nbcon_owner_matches() and nbcon_waiter_matches()
use a minimal set of data to determine if a context matches.
The existing kerneldoc and comments were not clear enough and
caused the printk folks to re-prove that the functions are
indeed reliable in all cases.
Update and expand the explanations so that it is clear that the
implementations are sufficient for all cases.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-6-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
Add validation that printk_deferred_enter()/_exit() are called in
non-migration contexts.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-5-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
If a non-boot console is registering and boot consoles exist,
the consoles are flushed before being unregistered. This allows
the non-boot console to continue where the boot console left
off.
If for whatever reason flushing fails, the lowest seq found from
any of the enabled boot consoles is used. Until now con->seq was
checked. However, if it is an nbcon boot console, the function
nbcon_seq_read() must be used to read seq because con->seq is
not updated for nbcon consoles.
Check if it is an nbcon boot console and if so call
nbcon_seq_read() to read seq.
Also, avoid usage of con->seq as temporary storage of the
starting record. Instead, rename console_init_seq() to
get_init_console_seq() and just return the value. For nbcon
consoles set the sequence via nbcon_seq_force(), for legacy
consoles set con->seq.
The cleaned design should make sure that the value stays and is
set before the console is added to the console list. It also
unifies the sequence number initialization for legacy and nbcon
consoles.
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Link: https://lore.kernel.org/r/20240820063001.36405-4-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
Rather than splitting the nbcon allocation and initialization into
two pieces, perform all initialization in nbcon_alloc(). Later,
the initial sequence is calculated and can be explicitly set using
nbcon_seq_force(). This removes the need for the strong rules of
nbcon_init() that even included a BUG_ON().
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-3-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
kernel/printk/printk.c:284:5: sparse: sparse: context imbalance in
'console_srcu_read_lock' - wrong count at exit
include/linux/srcu.h:301:9: sparse: sparse: context imbalance in
'console_srcu_read_unlock' - unexpected unlock
Fixes: 6c4afa79147e ("printk: Prepare for SRCU console list protection")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/r/20240820063001.36405-2-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
Calling va_start / va_end multiple times is undefined and causes
problems with certain compiler / platforms.
Change alloc_ordered_workqueue_lockdep_map to a macro and updated
__alloc_workqueue to take a va_list argument.
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
use_parent_ecpus is used to track whether the children are using the
parent's effective_cpus. When a parent's effective_cpus is changed
due to changes in a child partition's effective_xcpus, any child
using parent'effective_cpus must call update_cpumasks_hier. However,
if a child is not a valid partition, it is sufficient to determine
whether to call update_cpumasks_hier based on whether the child's
effective_cpus is going to change. To make the code more succinct,
it is suggested to remove use_parent_ecpus.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Both fetch_xcpus and user_xcpus functions are used to retrieve the value
of exclusive_cpus. If exclusive_cpus is not set, cpus_allowed is the
implicit value used as exclusive in a local partition. I can not imagine
a scenario where effective_xcpus is not empty when exclusive_cpus is
empty. Therefore, I suggest removing the fetch_xcpus function.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
When enable a remote partition, I found that:
cd /sys/fs/cgroup/
mkdir test
mkdir test/test1
echo +cpuset > cgroup.subtree_control
echo +cpuset > test/cgroup.subtree_control
echo 3 > test/test1/cpuset.cpus
echo root > test/test1/cpuset.cpus.partition
cat test/test1/cpuset.cpus.partition
root invalid (Parent is not a partition root)
The parent of a remote partition could not be a root. This is due to the
emtpy effective_xcpus. It would be better to prompt the message "invalid
cpu list in cpuset.cpus.exclusive".
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
When soft interrupt actions are called, they are passed a pointer to the
struct softirq action which contains the action's function pointer.
This pointer isn't useful, as the action callback already knows what
function it is. And since each callback handles a specific soft interrupt,
the callback also knows which soft interrupt number is running.
No soft interrupt action callback actually uses this parameter, so remove
it from the function pointer signature. This clarifies that soft interrupt
actions are global routines and makes it slightly cheaper to call them.
Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/all/20240815171549.3260003-1-csander@purestorage.com
The unification of irq_domain_create_legacy() missed the fact that
interrupts must be associated even when the Linux interrupt number provided
in the first_irq argument is 0.
This breaks all call sites of irq_domain_create_legacy() which supply 0 as
the first_irq argument.
Enforce the association for legacy domains in __irq_domain_instantiate() to
cure this.
[ tglx: Massaged it slightly. ]
Fixes: 70114e7f7585 ("irqdomain: Simplify simple and legacy domain creation")
Reported-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by Matti Vaittinen <mazziesaccount@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Link: https://lore.kernel.org/all/c3379142-10bc-4f14-b8ac-a46927aeac38@gmail.com
iounmap() on x86 occasionally fails to unmap because the provided valid
ioremap address is not below high_memory. It turned out that this
happens due to KASLR.
KASLR uses the full address space between PAGE_OFFSET and vaddr_end to
randomize the starting points of the direct map, vmalloc and vmemmap
regions. It thereby limits the size of the direct map by using the
installed memory size plus an extra configurable margin for hot-plug
memory. This limitation is done to gain more randomization space
because otherwise only the holes between the direct map, vmalloc,
vmemmap and vaddr_end would be usable for randomizing.
The limited direct map size is not exposed to the rest of the kernel, so
the memory hot-plug and resource management related code paths still
operate under the assumption that the available address space can be
determined with MAX_PHYSMEM_BITS.
request_free_mem_region() allocates from (1 << MAX_PHYSMEM_BITS) - 1
downwards. That means the first allocation happens past the end of the
direct map and if unlucky this address is in the vmalloc space, which
causes high_memory to become greater than VMALLOC_START and consequently
causes iounmap() to fail for valid ioremap addresses.
MAX_PHYSMEM_BITS cannot be changed for that because the randomization
does not align with address bit boundaries and there are other places
which actually require to know the maximum number of address bits. All
remaining usage sites of MAX_PHYSMEM_BITS have been analyzed and found
to be correct.
Cure this by exposing the end of the direct map via PHYSMEM_END and use
that for the memory hot-plug and resource management related places
instead of relying on MAX_PHYSMEM_BITS. In the KASLR case PHYSMEM_END
maps to a variable which is initialized by the KASLR initialization and
otherwise it is based on MAX_PHYSMEM_BITS as before.
To prevent future hickups add a check into add_pages() to catch callers
trying to add memory above PHYSMEM_END.
Fixes: 0483e1fa6e09 ("x86/mm: Implement ASLR for kernel memory regions")
Reported-by: Max Ramanouski <max8rr8@gmail.com>
Reported-by: Alistair Popple <apopple@nvidia.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-By: Max Ramanouski <max8rr8@gmail.com>
Tested-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Alistair Popple <apopple@nvidia.com>
Reviewed-by: Kees Cook <kees@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/87ed6soy3z.ffs@tglx
The comment in cgroup_file_write is missing some interfaces, such as
'cgroup.threads'. All delegatable files are listed in
'/sys/kernel/cgroup/delegate', so update the comment in cgroup_file_write.
Besides, add a statement that files outside the namespace shouldn't be
visible from inside the delegated namespace.
tj: Reflowed text for consistency.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Merge tag 'printk-for-6.11-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk fix from Petr Mladek:
- Do not block printk on non-panic CPUs when they are dumping
backtraces
* tag 'printk-for-6.11-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk/panic: Allow cpu backtraces to be written into ringbuffer during panic
the others pertain to post-6.10 issues.
As usual with these merges, singletons and doubletons all over the place,
no identifiable-by-me theme. Please see the lovingly curated changelogs
to get the skinny.
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Merge tag 'mm-hotfixes-stable-2024-08-17-19-34' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull misc fixes from Andrew Morton:
"16 hotfixes. All except one are for MM. 10 of these are cc:stable and
the others pertain to post-6.10 issues.
As usual with these merges, singletons and doubletons all over the
place, no identifiable-by-me theme. Please see the lovingly curated
changelogs to get the skinny"
* tag 'mm-hotfixes-stable-2024-08-17-19-34' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
mm/migrate: fix deadlock in migrate_pages_batch() on large folios
alloc_tag: mark pages reserved during CMA activation as not tagged
alloc_tag: introduce clear_page_tag_ref() helper function
crash: fix riscv64 crash memory reserve dead loop
selftests: memfd_secret: don't build memfd_secret test on unsupported arches
mm: fix endless reclaim on machines with unaccepted memory
selftests/mm: compaction_test: fix off by one in check_compaction()
mm/numa: no task_numa_fault() call if PMD is changed
mm/numa: no task_numa_fault() call if PTE is changed
mm/vmalloc: fix page mapping if vm_area_alloc_pages() with high order fallback to order 0
mm/memory-failure: use raw_spinlock_t in struct memory_failure_cpu
mm: don't account memmap per-node
mm: add system wide stats items category
mm: don't account memmap on failure
mm/hugetlb: fix hugetlb vs. core-mm PT locking
mseal: fix is_madv_discard()
- Fix crashes on 85xx with some configs since the recent hugepd rework.
- Fix boot warning with hugepages and CONFIG_DEBUG_VIRTUAL on some platforms.
- Don't enable offline cores when changing SMT modes, to match existing
userspace behaviour.
Thanks to: Christophe Leroy, Dr. David Alan Gilbert, Guenter Roeck, Nysal Jan
K.A, Shrikanth Hegde, Thomas Gleixner, Tyrel Datwyler.
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Merge tag 'powerpc-6.11-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux
Pull powerpc fixes from Michael Ellerman:
- Fix crashes on 85xx with some configs since the recent hugepd rework.
- Fix boot warning with hugepages and CONFIG_DEBUG_VIRTUAL on some
platforms.
- Don't enable offline cores when changing SMT modes, to match existing
userspace behaviour.
Thanks to Christophe Leroy, Dr. David Alan Gilbert, Guenter Roeck, Nysal
Jan K.A, Shrikanth Hegde, Thomas Gleixner, and Tyrel Datwyler.
* tag 'powerpc-6.11-2' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
powerpc/topology: Check if a core is online
cpu/SMT: Enable SMT only if a core is online
powerpc/mm: Fix boot warning with hugepages and CONFIG_DEBUG_VIRTUAL
powerpc/mm: Fix size of allocated PGDIR
soc: fsl: qbman: remove unused struct 'cgr_comp'
When submitting more than 2^32 padata objects to padata_do_serial, the
current sorting implementation incorrectly sorts padata objects with
overflowed seq_nr, causing them to be placed before existing objects in
the reorder list. This leads to a deadlock in the serialization process
as padata_find_next cannot match padata->seq_nr and pd->processed
because the padata instance with overflowed seq_nr will be selected
next.
To fix this, we use an unsigned integer wrap around to correctly sort
padata objects in scenarios with integer overflow.
Fixes: bfde23ce200e ("padata: unbind parallel jobs from specific CPUs")
Cc: <stable@vger.kernel.org>
Co-developed-by: Christian Gafert <christian.gafert@rohde-schwarz.com>
Signed-off-by: Christian Gafert <christian.gafert@rohde-schwarz.com>
Co-developed-by: Max Ferger <max.ferger@rohde-schwarz.com>
Signed-off-by: Max Ferger <max.ferger@rohde-schwarz.com>
Signed-off-by: Van Giang Nguyen <vangiang.nguyen@rohde-schwarz.com>
Acked-by: Daniel Jordan <daniel.m.jordan@oracle.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
- Prevent a NULL pointer dereference in the error path of RTLA tool
- Fix an infinite loop bug when reading from the ring buffer when closed.
If there's a thread trying to read the ring buffer and it gets closed
by another thread, the one reading will go into an infinite loop
when the buffer is empty instead of exiting back to user space.
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Merge tag 'trace-v6.11-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
Pull tracing fixes from Steven Rostedt:
"A couple of fixes for tracing:
- Prevent a NULL pointer dereference in the error path of RTLA tool
- Fix an infinite loop bug when reading from the ring buffer when
closed. If there's a thread trying to read the ring buffer and it
gets closed by another thread, the one reading will go into an
infinite loop when the buffer is empty instead of exiting back to
user space"
* tag 'trace-v6.11-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
rtla/osnoise: Prevent NULL dereference in error handling
tracing: Return from tracing_buffers_read() if the file has been closed
On RISCV64 Qemu machine with 512MB memory, cmdline "crashkernel=500M,high"
will cause system stall as below:
Zone ranges:
DMA32 [mem 0x0000000080000000-0x000000009fffffff]
Normal empty
Movable zone start for each node
Early memory node ranges
node 0: [mem 0x0000000080000000-0x000000008005ffff]
node 0: [mem 0x0000000080060000-0x000000009fffffff]
Initmem setup node 0 [mem 0x0000000080000000-0x000000009fffffff]
(stall here)
commit 5d99cadf1568 ("crash: fix x86_32 crash memory reserve dead loop
bug") fix this on 32-bit architecture. However, the problem is not
completely solved. If `CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX` on
64-bit architecture, for example, when system memory is equal to
CRASH_ADDR_LOW_MAX on RISCV64, the following infinite loop will also
occur:
-> reserve_crashkernel_generic() and high is true
-> alloc at [CRASH_ADDR_LOW_MAX, CRASH_ADDR_HIGH_MAX] fail
-> alloc at [0, CRASH_ADDR_LOW_MAX] fail and repeatedly
(because CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX).
As Catalin suggested, do not remove the ",high" reservation fallback to
",low" logic which will change arm64's kdump behavior, but fix it by
skipping the above situation similar to commit d2f32f23190b ("crash: fix
x86_32 crash memory reserve dead loop").
After this patch, it print:
cannot allocate crashkernel (size:0x1f400000)
Link: https://lkml.kernel.org/r/20240812062017.2674441-1-ruanjinjie@huawei.com
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Dave Young <dyoung@redhat.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
With CONFIG_LTO_CLANG=y, the compiler may add .llvm.<hash> suffix to
function names to avoid duplication. APIs like kallsyms_lookup_name()
and kallsyms_on_each_match_symbol() tries to match these symbol names
without the .llvm.<hash> suffix, e.g., match "c_stop" with symbol
c_stop.llvm.17132674095431275852. This turned out to be problematic
for use cases that require exact match, for example, livepatch.
Fix this by making the APIs to match symbols exactly.
Also cleanup kallsyms_selftests accordingly.
Signed-off-by: Song Liu <song@kernel.org>
Fixes: 8cc32a9bbf29 ("kallsyms: strip LTO-only suffixes from promoted global functions")
Tested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20240807220513.3100483-3-song@kernel.org
Signed-off-by: Kees Cook <kees@kernel.org>
The "rcu_dyntick" naming convention has been turned into "rcu_watching" for
all helpers now, align the trace event to that.
To add to the confusion, the strings passed to the trace event are now
reversed: when RCU "starts" the dyntick / EQS state, it "stops" watching.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.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>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, drop the dyntick reference and update the name of this helper
to express that it rechecks rdp->watching_snap after an earlier
rcu_watching_snap_save().
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, and the 'dynticks' prefix can be dropped without losing any
meaning.
Suggested-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, and the snapshot helpers are now prefix by
"rcu_watching". Reflect that change into the storage variables for these
snapshots.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, and the snapshot helpers are now prefix by
"rcu_watching". Reflect that change into the storage variables for these
snapshots.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, reflect that change in the related helpers.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, the dynticks prefix can go.
While at it, this helper is only meant to be called after failing an
earlier call to rcu_watching_snap_in_eqs(), document this in the comments
and add a WARN_ON_ONCE() for good measure.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, reflect that change in the related helpers.
While at it, update a comment that still refers to rcu_dynticks_snap(),
which was removed by commit:
7be2e6323b9b ("rcu: Remove full memory barrier on RCU stall printout")
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, reflect that change in the related helpers.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, reflect that change in the related helpers.
Note that "watching" is the opposite of "in EQS", so the negation is lifted
out of the helper and into the callsites.
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
RCU_WATCHING, and the 'dynticks' prefix can be dropped without losing any
meaning.
While at it, flip the suffixes of these helpers. We are not telling
that we are entering dynticks mode from an RCU-task perspective anymore; we
are telling that we are exiting RCU-tasks because we are in eqs mode.
[ neeraj.upadhyay: Incorporate Frederic Weisbecker feedback. ]
Suggested-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
rt_mutex_handle_deadlock() is called with rt_mutex::wait_lock held. In the
good case it returns with the lock held and in the deadlock case it emits a
warning and goes into an endless scheduling loop with the lock held, which
triggers the 'scheduling in atomic' warning.
Unlock rt_mutex::wait_lock in the dead lock case before issuing the warning
and dropping into the schedule for ever loop.
[ tglx: Moved unlock before the WARN(), removed the pointless comment,
massaged changelog, added Fixes tag ]
Fixes: 3d5c9340d194 ("rtmutex: Handle deadlock detection smarter")
Signed-off-by: Roland Xu <mu001999@outlook.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/ME0P300MB063599BEF0743B8FA339C2CECC802@ME0P300MB0635.AUSP300.PROD.OUTLOOK.COM
'struct ref_scale_ops' are not modified in these drivers.
Constifying this structure moves some data to a read-only section, so
increase overall security.
On a x86_64, with allmodconfig:
Before:
======
text data bss dec hex filename
34231 4167 736 39134 98de kernel/rcu/refscale.o
After:
=====
text data bss dec hex filename
35175 3239 736 39150 98ee kernel/rcu/refscale.o
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Tested-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The current rcu_scale_writer() asynchronous grace-period testing uses a
per-CPU counter to track the number of outstanding callbacks. This is
subject to CPU-imbalance errors when tasks migrate from one CPU to another
between the time that the counter is incremented and the callback is
queued, and additionally in kernels configured such that callbacks can
be invoked on some CPU other than the one that queued it.
This commit therefore arranges for per-task callback counts, thus avoiding
any issues with migration of either tasks or callbacks.
Reported-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Currently, if someone modprobes and rmmods rcuscale successfully, but
the next run errors out during the modprobe, non-NULL pointers to freed
memory will remain. If the run after that also errors out during the
modprobe, there will be double-free bugs.
This commit therefore NULLs out top-level pointers to memory that has
just been freed.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The rcu_scale_writer() function needs only a fixed number of rcu_head
structures per kthread, which means that a trivial allocator suffices.
This commit therefore uses an llist-based allocator using a fixed array of
structures per kthread. This allows aggressive testing of RCU performance
without stressing the slab allocators.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Under some conditions, kmalloc(GFP_KERNEL) allocations have been
observed to repeatedly fail. This situation has been observed to
cause one of the rcu_scale_writer() instances to loop indefinitely
retrying memory allocation for an asynchronous grace-period primitive.
The problem is that if memory is short, all the other instances will
allocate all available memory before the looping task is awakened from
its rcu_barrier*() call. This in turn results in hangs, so that rcuscale
fails to complete.
This commit therefore removes the tight retry loop, so that when this
condition occurs, the affected task is still passing through the full
loop with its full set of termination checks. This spreads the risk
of indefinite memory-allocation retry failures across all instances of
rcu_scale_writer() tasks, which in turn prevents the hangs.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
This commit causes all writer tasks to provide a brief report after a
hang has been reported, spaced at one-second intervals.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Currently, if the rcuscale module's async module parameter is specified
for RCU implementations that do not have async primitives such as RCU
Tasks Rude (which now lacks a call_rcu_tasks_rude() function), there
will be a series of splats due to calls to a NULL pointer. This commit
therefore warns of this situation, but switches to non-async testing.
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The commit 2d7f00b2f0130 ("rcu: Suppress smp_processor_id() complaint
in synchronize_rcu_expedited_wait()") disabled preemption around
dump_cpu_task() to suppress warning on its usage within preemtible context.
Calling dump_cpu_task() doesn't required to be in non-preemptible context
except for suppressing the smp_processor_id() warning.
As the smp_processor_id() is evaluated along with in_hardirq()
to check if it's in interrupt context, this patch removes the need
for its preemtion disablement by reordering the condition so that
smp_processor_id() only gets evaluated when it's in interrupt context.
Signed-off-by: Ryo Takakura <takakura@valinux.co.jp>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
During CSD-lock stalls, the additional information output by expedited
RCU CPU stall warnings is usually redundant, flooding the console for
not good reason. However, this has been the way things work for a few
years. This commit therefore uses rcutree.csd_lock_suppress_rcu_stall
kernel boot parameter that causes expedited RCU CPU stall warnings to
be abbreviated to a single line when there is at least one CPU that has
been stuck waiting for CSD lock for more than five seconds.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
This commit extracts the RCU CPU stall-warning report code from
synchronize_rcu_expedited_wait() and places it in a new function named
synchronize_rcu_expedited_stall(). This is strictly a code-movement
commit. A later commit will use this reorganization to avoid printing
expedited RCU CPU stall warnings while there are ongoing CSD-lock stall
reports.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
During CSD-lock stalls, the additional information output by RCU CPU
stall warnings is usually redundant, flooding the console for not good
reason. However, this has been the way things work for a few years.
This commit therefore adds an rcutree.csd_lock_suppress_rcu_stall kernel
boot parameter that causes RCU CPU stall warnings to be abbreviated to
a single line when there is at least one CPU that has been stuck waiting
for CSD lock for more than five seconds.
To make this abbreviated message happen with decent probability:
tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 8 \
--configs "2*TREE01" --kconfig "CONFIG_CSD_LOCK_WAIT_DEBUG=y" \
--bootargs "csdlock_debug=1 rcutorture.stall_cpu=200 \
rcutorture.stall_cpu_holdoff=120 rcutorture.stall_cpu_irqsoff=1 \
rcutree.csd_lock_suppress_rcu_stall=1 \
rcupdate.rcu_exp_cpu_stall_timeout=5000" --trust-make
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
About 40% of all csd_lock warnings observed in our fleet appear to
be due to sched_clock() going backward in time (usually only a little
bit), resulting in ts0 being larger than ts2.
When the local CPU is at fault, we should print out a message reflecting
that, rather than trying to get the remote CPU's stack trace.
Signed-off-by: Rik van Riel <riel@surriel.com>
Tested-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Currently, the CSD-lock diagnostics in CONFIG_CSD_LOCK_WAIT_DEBUG=y
kernels are emitted at five-second intervals. Although this has proven
to be a good time interval for the first diagnostic, if the target CPU
keeps interrupts disabled for way longer than five seconds, the ratio
of useful new information to pointless repetition increases considerably.
Therefore, back off the time period for repeated reports of the same
incident, increasing linearly with the number of reports and logarithmicly
with the number of online CPUs.
[ paulmck: Apply Dan Carpenter feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Imran Khan <imran.f.khan@oracle.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Leonardo Bras <leobras@redhat.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Reviewed-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
