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ftrace: Disable preemption in the tracepoint callbacks handling filtered pids

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When function trace PID filtering is enabled, the function tracer will
attach a callback to the fork tracepoint as well as the exit tracepoint
that will add the forked child PID to the PID filtering list as well as
remove the PID that is exiting.

Commit a46023d561 ("tracing: Guard __DECLARE_TRACE() use of
__DO_TRACE_CALL() with SRCU-fast") removed the disabling of preemption
when calling tracepoint callbacks.

The callbacks used for the PID filtering accounting depended on preemption
being disabled, and now the trigger a "suspicious RCU usage" warning message.

Make them explicitly disable preemption.

Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20260302213546.156e3e4f@gandalf.local.home
Fixes: a46023d561 ("tracing: Guard __DECLARE_TRACE() use of __DO_TRACE_CALL() with SRCU-fast")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
This commit is contained in:
Steven Rostedt 2026-03-02 21:35:46 -05:00 • committed by Steven Rostedt (Google)
parent 0a663b764d
commit cc337974cd
1 changed files with 2 additions and 0 deletions
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2
kernel/trace/ftrace.c
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@ -8611,6 +8611,7 @@ ftrace_pid_follow_sched_process_fork(void *data,
struct trace_pid_list *pid_list;
struct trace_array *tr = data;
guard(preempt)();
pid_list = rcu_dereference_sched(tr->function_pids);
trace_filter_add_remove_task(pid_list, self, task);
@ -8624,6 +8625,7 @@ ftrace_pid_follow_sched_process_exit(void *data, struct task_struct *task)
struct trace_pid_list *pid_list;
struct trace_array *tr = data;
guard(preempt)();
pid_list = rcu_dereference_sched(tr->function_pids);
trace_filter_add_remove_task(pid_list, NULL, task);