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| author | pengdonglin <pengdonglin@xiaomi.com> | 2025-05-12 17:42:45 +0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-05-22 14:08:25 +0200 |
| commit | deea40f26b9ded46a9e6e50103dc103453725f56 (patch) | |
| tree | e6ea698f72c7801df3d46d6aa875bde86690a374 | |
| parent | 466ef37d5545d2b6a633c5316cf349f5b6942c3c (diff) | |
| download | linux-deea40f26b9ded46a9e6e50103dc103453725f56.tar.gz linux-deea40f26b9ded46a9e6e50103dc103453725f56.tar.bz2 linux-deea40f26b9ded46a9e6e50103dc103453725f56.zip | |
ftrace: Fix preemption accounting for stacktrace trigger command
commit e333332657f615ac2b55aa35565c4a882018bbe9 upstream.
When using the stacktrace trigger command to trace syscalls, the
preemption count was consistently reported as 1 when the system call
event itself had 0 (".").
For example:
root@ubuntu22-vm:/sys/kernel/tracing/events/syscalls/sys_enter_read
$ echo stacktrace > trigger
$ echo 1 > enable
sshd-416 [002] ..... 232.864910: sys_read(fd: a, buf: 556b1f3221d0, count: 8000)
sshd-416 [002] ...1. 232.864913: <stack trace>
=> ftrace_syscall_enter
=> syscall_trace_enter
=> do_syscall_64
=> entry_SYSCALL_64_after_hwframe
The root cause is that the trace framework disables preemption in __DO_TRACE before
invoking the trigger callback.
Use the tracing_gen_ctx_dec() that will accommodate for the increase of
the preemption count in __DO_TRACE when calling the callback. The result
is the accurate reporting of:
sshd-410 [004] ..... 210.117660: sys_read(fd: 4, buf: 559b725ba130, count: 40000)
sshd-410 [004] ..... 210.117662: <stack trace>
=> ftrace_syscall_enter
=> syscall_trace_enter
=> do_syscall_64
=> entry_SYSCALL_64_after_hwframe
Cc: stable@vger.kernel.org
Fixes: ce33c845b030c ("tracing: Dump stacktrace trigger to the corresponding instance")
Link: https://lore.kernel.org/20250512094246.1167956-1-dolinux.peng@gmail.com
Signed-off-by: pengdonglin <dolinux.peng@gmail.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | kernel/trace/trace_events_trigger.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c index 106f9813841a..d56e208f5cb8 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -1244,7 +1244,7 @@ stacktrace_trigger(struct event_trigger_data *data, struct trace_event_file *file = data->private_data; if (file) - __trace_stack(file->tr, tracing_gen_ctx(), STACK_SKIP); + __trace_stack(file->tr, tracing_gen_ctx_dec(), STACK_SKIP); else trace_dump_stack(STACK_SKIP); } |