From: pengdonglin <pengdong...@xiaomi.com>
While using the stacktrace filter command to trace ksys_read, I noticed
that the preemption count was consistently reported as 1, which seemed
incorrect:
$ echo ksys_read:stacktrace > set_ftrace_filter
<...>-453 [004] ...1. 38.308956: <stack trace>
=> ksys_read
=> do_syscall_64
=> entry_SYSCALL_64_after_hwframe
The root cause is that the trace framework disables preemption when
invoking the filter command callback in function_trace_probe_call:
preempt_disable_notrace();
probe_ops->func(ip, parent_ip, probe_opsbe->tr, probe_ops, probe->data);
preempt_enable_notrace();
This patch uses tracing_gen_ctx_dec() to obtain the correct preemption
count within the callback, resulting in accurate reporting:
$ echo ksys_read:stacktrace > set_ftrace_filter
<...>-410 [006] ..... 31.420396: <stack trace>
=> ksys_read
=> do_syscall_64
=> entry_SYSCALL_64_after_hwframe
Signed-off-by: pengdonglin <dolinux.p...@gmail.com>
---
kernel/trace/trace_functions.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index 98ccf3f00c51..4e37a0f6aaa3 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -633,11 +633,7 @@ ftrace_traceoff(unsigned long ip, unsigned long parent_ip,
static __always_inline void trace_stack(struct trace_array *tr)
{
- unsigned int trace_ctx;
-
- trace_ctx = tracing_gen_ctx();
-
- __trace_stack(tr, trace_ctx, FTRACE_STACK_SKIP);
+ __trace_stack(tr, tracing_gen_ctx_dec(), FTRACE_STACK_SKIP);
}
static void
--
2.25.1
