[PATCH v2] exit: add exit_code to trace_sched_process_exit and move it earlier in do_exit()

[wenyang.linux@foxmail.com]

From: Wen Yang <wenyang.linux@foxmail.com>

Currently coredump_task_exit() takes some time to wait for the generation
of the dump file. But if the user-space wants to receive a notification
as soon as possible it maybe inconvenient.

Add exit_code to the TP trace_sched_process_exit() and move it earlier in
do_exit(). This way a user-space monitor could detect the exits and
potentially make some preparations in advance.

Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Wen Yang <wenyang.linux@foxmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org
---
 include/trace/events/sched.h | 28 +++++++++++++++++++++++++---
 kernel/exit.c                |  2 +-
 2 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index dbb01b4b7451..c2e8655fd453 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -330,9 +330,31 @@ DEFINE_EVENT(sched_process_template, sched_process_free,
 /*
  * Tracepoint for a task exiting:
  */
-DEFINE_EVENT(sched_process_template, sched_process_exit,
-	     TP_PROTO(struct task_struct *p),
-	     TP_ARGS(p));
+TRACE_EVENT(sched_process_exit,
+
+	TP_PROTO(struct task_struct *task, long code),
+
+	TP_ARGS(task, code),
+
+	TP_STRUCT__entry(
+		__array(	char,	comm,	TASK_COMM_LEN	)
+		__field(	pid_t,	pid			)
+		__field(	int,	prio			)
+		__field(	long,	code			)
+	),
+
+	TP_fast_assign(
+		memcpy(__entry->comm, task->comm, TASK_COMM_LEN);
+		__entry->pid		= task->pid;
+		__entry->prio		= task->prio;
+		__entry->code		= code;
+	),
+
+	TP_printk("comm=%s pid=%d prio=%d exit_code=0x%lx",
+		  __entry->comm, __entry->pid, __entry->prio,
+		  __entry->code)
+);
+
 
 /*
  * Tracepoint for waiting on task to unschedule:
diff --git a/kernel/exit.c b/kernel/exit.c
index 493647fd7c07..48b6ed7f7760 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -826,6 +826,7 @@ void __noreturn do_exit(long code)
 
 	WARN_ON(tsk->plug);
 
+	trace_sched_process_exit(tsk, code);
 	kcov_task_exit(tsk);
 	kmsan_task_exit(tsk);
 
@@ -866,7 +867,6 @@ void __noreturn do_exit(long code)
 
 	if (group_dead)
 		acct_process();
-	trace_sched_process_exit(tsk);
 
 	exit_sem(tsk);
 	exit_shm(tsk);
-- 
2.25.1