From 3ca55ca225d7627e76fcfe2894740c4f615ff2e0 Mon Sep 17 00:00:00 2001 From: Andrii Nakryiko Date: Wed, 2 Apr 2025 11:09:25 -0700 Subject: exit: move and extend sched_process_exit() tracepoint It is useful to be able to access current->mm at task exit to, say, record a bunch of VMA information right before the task exits (e.g., for stack symbolization reasons when dealing with short-lived processes that exit in the middle of profiling session). Currently, trace_sched_process_exit() is triggered after exit_mm() which resets current->mm to NULL making this tracepoint unsuitable for inspecting and recording task's mm_struct-related data when tracing process lifetimes. There is a particularly suitable place, though, right after taskstats_exit() is called, but before we do exit_mm() and other exit_*() resource teardowns. taskstats performs a similar kind of accounting that some applications do with BPF, and so co-locating them seems like a good fit. So that's where trace_sched_process_exit() is moved with this patch. Also, existing trace_sched_process_exit() tracepoint is notoriously missing `group_dead` flag that is certainly useful in practice and some of our production applications have to work around this. So plumb `group_dead` through while at it, to have a richer and more complete tracepoint. Note that we can't use sched_process_template anymore, and so we use TRACE_EVENT()-based tracepoint definition. But all the field names and order, as well as assign and output logic remain intact. We just add one extra field at the end in backwards-compatible way. [andrii@kernel.org: document sched_process_exit and sched_process_template relation] Link: https://lkml.kernel.org/r/20250403174120.4087794-1-andrii@kernel.org Link: https://lkml.kernel.org/r/20250402180925.90914-1-andrii@kernel.org Signed-off-by: Andrii Nakryiko Acked-by: Steven Rostedt (Google) Acked-by: Oleg Nesterov Suggested-by: Ingo Molnar Cc: Alexander Potapenko Cc: Christian Brauner Cc: "Masami Hiramatsu (Google)" Cc: Mathieu Desnoyers Cc: Michal Hocko Signed-off-by: Andrew Morton --- kernel/exit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/exit.c b/kernel/exit.c index 1b51dc099f1e..f1db86dcbeb1 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -936,12 +936,12 @@ void __noreturn do_exit(long code) tsk->exit_code = code; taskstats_exit(tsk, group_dead); + trace_sched_process_exit(tsk, group_dead); exit_mm(); if (group_dead) acct_process(); - trace_sched_process_exit(tsk); exit_sem(tsk); exit_shm(tsk); -- cgit v1.2.3