6.6-stable review patch. If anyone has any objections, please let me know.
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From: pengdonglin pengdonglin@xiaomi.com
commit 11aff32439df6ca5b3b891b43032faf88f4a6a29 upstream.
The preemption count of the stacktrace filter command to trace ksys_read is consistently 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();
Use tracing_gen_ctx_dec() to account for the preempt_disable_notrace(), which will output the correct preemption count:
$ echo ksys_read:stacktrace > set_ftrace_filter
<...>-410 [006] ..... 31.420396: <stack trace> => ksys_read => do_syscall_64 => entry_SYSCALL_64_after_hwframe
Cc: stable@vger.kernel.org Fixes: 36590c50b2d07 ("tracing: Merge irqflags + preempt counter.") Link: https://lore.kernel.org/20250512094246.1167956-2-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 --- kernel/trace/trace_functions.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-)
--- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c @@ -561,11 +561,7 @@ ftrace_traceoff(unsigned long ip, unsign
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