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Tracing updates for 6.13:

Browse Source 
- Add trace flag for NEED_RESCHED_LAZY
 
   Now that NEED_RESCHED_LAZY is upstream, add it to the status bits of the
   common_flags. This will now show when the NEED_RESCHED_LAZY flag is set that
   is used for debugging latency issues in the kernel via a trace.
 
 - Remove leftover "__idx" variable when SRCU was removed from the tracepoint
   code
 
 - Add rcu_tasks_trace guard
 
   To add a guard() around the tracepoint code, a rcu_tasks_trace guard needs
   to be created first.
 
 - Remove __DO_TRACE() macro and just call __DO_TRACE_CALL() directly
 
   The DO_TRACE() macro has conditional locking depending on what was passed
   into the macro parameters. As the guts of the macro has been moved to
   __DO_TRACE_CALL() to handle static call logic, there's no reason to keep
   the __DO_TRACE() macro around. It is better to just do the locking in
   place without the conditionals and call __DO_TRACE_CALL() from those
   locations. The "cond" passed in can also be moved out of that macro.
   This simplifies the code.
 
 - Remove the "cond" from the system call tracepoint macros
 
   The "cond" variable was added to allow some tracepoints to check a
   condition within the static_branch (jump/nop) logic. The system calls do
   not need this. Removing it simplifies the code.
 
 - Replace scoped_guard() with just guard() in the tracepoint logic
 
   guard() works just as well as scoped_guard() in the tracepoint logic and
   the scoped_guard() causes some issues.
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Merge tag 'trace-v6.13-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull more tracing updates from Steven Rostedt:

 - Add trace flag for NEED_RESCHED_LAZY

   Now that NEED_RESCHED_LAZY is upstream, add it to the status bits of
   the common_flags. This will now show when the NEED_RESCHED_LAZY flag
   is set that is used for debugging latency issues in the kernel via a
   trace.

 - Remove leftover "__idx" variable when SRCU was removed from the
   tracepoint code

 - Add rcu_tasks_trace guard

   To add a guard() around the tracepoint code, a rcu_tasks_trace guard
   needs to be created first.

 - Remove __DO_TRACE() macro and just call __DO_TRACE_CALL() directly

   The DO_TRACE() macro has conditional locking depending on what was
   passed into the macro parameters. As the guts of the macro has been
   moved to __DO_TRACE_CALL() to handle static call logic, there's no
   reason to keep the __DO_TRACE() macro around.

   It is better to just do the locking in place without the conditionals
   and call __DO_TRACE_CALL() from those locations. The "cond" passed in
   can also be moved out of that macro. This simplifies the code.

 - Remove the "cond" from the system call tracepoint macros

   The "cond" variable was added to allow some tracepoints to check a
   condition within the static_branch (jump/nop) logic. The system calls
   do not need this. Removing it simplifies the code.

 - Replace scoped_guard() with just guard() in the tracepoint logic

   guard() works just as well as scoped_guard() in the tracepoint logic
   and the scoped_guard() causes some issues.

* tag 'trace-v6.13-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  tracing: Use guard() rather than scoped_guard()
  tracing: Remove cond argument from __DECLARE_TRACE_SYSCALL
  tracing: Remove conditional locking from __DO_TRACE()
  rcupdate_trace: Define rcu_tasks_trace lock guard
  tracing: Remove __idx variable from __DO_TRACE
  tracing: Move it_func[0] comment to the relevant context
  tracing: Record task flag NEED_RESCHED_LAZY.
This commit is contained in:
Linus Torvalds 2024-11-28 11:46:13 -08:00
commit 7af08b57bc
6 changed files with 55 additions and 53 deletions
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4
Documentation/trace/ftrace.rst
View File

@ -1033,9 +1033,13 @@ explains which is which.
irqs-off: 'd' interrupts are disabled. '.' otherwise.
need-resched:
- 'B' all, TIF_NEED_RESCHED, PREEMPT_NEED_RESCHED and TIF_RESCHED_LAZY is set,
- 'N' both TIF_NEED_RESCHED and PREEMPT_NEED_RESCHED is set,
- 'n' only TIF_NEED_RESCHED is set,
- 'p' only PREEMPT_NEED_RESCHED is set,
- 'L' both PREEMPT_NEED_RESCHED and TIF_RESCHED_LAZY is set,
- 'b' both TIF_NEED_RESCHED and TIF_RESCHED_LAZY is set,
- 'l' only TIF_RESCHED_LAZY is set
- '.' otherwise.
hardirq/softirq:

5
include/linux/rcupdate_trace.h
View File

@ -10,6 +10,7 @@
#include <linux/sched.h>
#include <linux/rcupdate.h>
#include <linux/cleanup.h>
extern struct lockdep_map rcu_trace_lock_map;
@ -98,4 +99,8 @@ static inline void rcu_read_lock_trace(void) { BUG(); }
static inline void rcu_read_unlock_trace(void) { BUG(); }
#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
DEFINE_LOCK_GUARD_0(rcu_tasks_trace,
rcu_read_lock_trace(),
rcu_read_unlock_trace())
#endif /* __LINUX_RCUPDATE_TRACE_H */

1
include/linux/trace_events.h
View File

@ -184,6 +184,7 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status);
enum trace_flag_type {
TRACE_FLAG_IRQS_OFF = 0x01,
TRACE_FLAG_NEED_RESCHED_LAZY = 0x02,
TRACE_FLAG_NEED_RESCHED = 0x04,
TRACE_FLAG_HARDIRQ = 0x08,
TRACE_FLAG_SOFTIRQ = 0x10,

82
include/linux/tracepoint.h
View File

@ -209,36 +209,6 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
#define __DO_TRACE_CALL(name, args) __traceiter_##name(NULL, args)
#endif /* CONFIG_HAVE_STATIC_CALL */
/*
* it_func[0] is never NULL because there is at least one element in the array
* when the array itself is non NULL.
*
* With @syscall=0, the tracepoint callback array dereference is
* protected by disabling preemption.
* With @syscall=1, the tracepoint callback array dereference is
* protected by Tasks Trace RCU, which allows probes to handle page
* faults.
*/
#define __DO_TRACE(name, args, cond, syscall) \
do { \
int __maybe_unused __idx = 0; \
\
if (!(cond)) \
return; \
\
if (syscall) \
rcu_read_lock_trace(); \
else \
preempt_disable_notrace(); \
\
__DO_TRACE_CALL(name, TP_ARGS(args)); \
\
if (syscall) \
rcu_read_unlock_trace(); \
else \
preempt_enable_notrace(); \
} while (0)
/*
* Declare an exported function that Rust code can call to trigger this
* tracepoint. This function does not include the static branch; that is done
@ -262,7 +232,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
* site if it is not watching, as it will need to be active when the
* tracepoint is enabled.
*/
#define __DECLARE_TRACE_COMMON(name, proto, args, cond, data_proto) \
#define __DECLARE_TRACE_COMMON(name, proto, args, data_proto) \
extern int __traceiter_##name(data_proto); \
DECLARE_STATIC_CALL(tp_func_##name, __traceiter_##name); \
extern struct tracepoint __tracepoint_##name; \
@ -297,41 +267,43 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
}
#define __DECLARE_TRACE(name, proto, args, cond, data_proto) \
__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), cond, PARAMS(data_proto)) \
__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto)) \
static inline void __rust_do_trace_##name(proto) \
{ \
__DO_TRACE(name, \
TP_ARGS(args), \
TP_CONDITION(cond), 0); \
if (cond) { \
guard(preempt_notrace)(); \
__DO_TRACE_CALL(name, TP_ARGS(args)); \
} \
} \
static inline void trace_##name(proto) \
{ \
if (static_branch_unlikely(&__tracepoint_##name.key)) \
__DO_TRACE(name, \
TP_ARGS(args), \
TP_CONDITION(cond), 0); \
if (static_branch_unlikely(&__tracepoint_##name.key)) { \
if (cond) { \
guard(preempt_notrace)(); \
__DO_TRACE_CALL(name, TP_ARGS(args)); \
} \
} \
if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \
WARN_ONCE(!rcu_is_watching(), \
"RCU not watching for tracepoint"); \
} \
}
#define __DECLARE_TRACE_SYSCALL(name, proto, args, cond, data_proto) \
__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), cond, PARAMS(data_proto)) \
#define __DECLARE_TRACE_SYSCALL(name, proto, args, data_proto) \
__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto)) \
static inline void __rust_do_trace_##name(proto) \
{ \
__DO_TRACE(name, \
TP_ARGS(args), \
TP_CONDITION(cond), 1); \
guard(rcu_tasks_trace)(); \
__DO_TRACE_CALL(name, TP_ARGS(args)); \
} \
static inline void trace_##name(proto) \
{ \
might_fault(); \
if (static_branch_unlikely(&__tracepoint_##name.key)) \
__DO_TRACE(name, \
TP_ARGS(args), \
TP_CONDITION(cond), 1); \
if (IS_ENABLED(CONFIG_LOCKDEP) && (cond)) { \
if (static_branch_unlikely(&__tracepoint_##name.key)) { \
guard(rcu_tasks_trace)(); \
__DO_TRACE_CALL(name, TP_ARGS(args)); \
} \
if (IS_ENABLED(CONFIG_LOCKDEP)) { \
WARN_ONCE(!rcu_is_watching(), \
"RCU not watching for tracepoint"); \
} \
@ -341,6 +313,9 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
* We have no guarantee that gcc and the linker won't up-align the tracepoint
* structures, so we create an array of pointers that will be used for iteration
* on the tracepoints.
*
* it_func[0] is never NULL because there is at least one element in the array
* when the array itself is non NULL.
*/
#define __DEFINE_TRACE_EXT(_name, _ext, proto, args) \
static const char __tpstrtab_##_name[] \
@ -412,7 +387,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
#else /* !TRACEPOINTS_ENABLED */
#define __DECLARE_TRACE(name, proto, args, cond, data_proto) \
#define __DECLARE_TRACE_COMMON(name, proto, args, data_proto) \
static inline void trace_##name(proto) \
{ } \
static inline int \
@ -436,7 +411,11 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
return false; \
}
#define __DECLARE_TRACE_SYSCALL __DECLARE_TRACE
#define __DECLARE_TRACE(name, proto, args, cond, data_proto) \
__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto))
#define __DECLARE_TRACE_SYSCALL(name, proto, args, data_proto) \
__DECLARE_TRACE_COMMON(name, PARAMS(proto), PARAMS(args), PARAMS(data_proto))
#define DEFINE_TRACE_FN(name, reg, unreg, proto, args)
#define DEFINE_TRACE_SYSCALL(name, reg, unreg, proto, args)
@ -502,7 +481,6 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
#define DECLARE_TRACE_SYSCALL(name, proto, args) \
__DECLARE_TRACE_SYSCALL(name, PARAMS(proto), PARAMS(args), \
cpu_online(raw_smp_processor_id()), \
PARAMS(void *__data, proto))
#define TRACE_EVENT_FLAGS(event, flag)

2
kernel/trace/trace.c
View File

@ -2552,6 +2552,8 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status)
trace_flags |= TRACE_FLAG_NEED_RESCHED;
if (test_preempt_need_resched())
trace_flags |= TRACE_FLAG_PREEMPT_RESCHED;
if (IS_ENABLED(CONFIG_ARCH_HAS_PREEMPT_LAZY) && tif_test_bit(TIF_NEED_RESCHED_LAZY))
trace_flags |= TRACE_FLAG_NEED_RESCHED_LAZY;
return (trace_flags << 16) | (min_t(unsigned int, pc & 0xff, 0xf)) |
(min_t(unsigned int, migration_disable_value(), 0xf)) << 4;
}

14
kernel/trace/trace_output.c
View File

@ -462,17 +462,29 @@ int trace_print_lat_fmt(struct trace_seq *s, struct trace_entry *entry)
bh_off ? 'b' :
'.';
switch (entry->flags & (TRACE_FLAG_NEED_RESCHED |
switch (entry->flags & (TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_NEED_RESCHED_LAZY |
TRACE_FLAG_PREEMPT_RESCHED)) {
case TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_NEED_RESCHED_LAZY | TRACE_FLAG_PREEMPT_RESCHED:
need_resched = 'B';
break;
case TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_PREEMPT_RESCHED:
need_resched = 'N';
break;
case TRACE_FLAG_NEED_RESCHED_LAZY | TRACE_FLAG_PREEMPT_RESCHED:
need_resched = 'L';
break;
case TRACE_FLAG_NEED_RESCHED | TRACE_FLAG_NEED_RESCHED_LAZY:
need_resched = 'b';
break;
case TRACE_FLAG_NEED_RESCHED:
need_resched = 'n';
break;
case TRACE_FLAG_PREEMPT_RESCHED:
need_resched = 'p';
break;
case TRACE_FLAG_NEED_RESCHED_LAZY:
need_resched = 'l';
break;
default:
need_resched = '.';
break;