From: Wen Yang <[email protected]>
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.
Commit 2d4bcf886e42 ("exit: Remove profile_task_exit & profile_munmap")
simplified the code, but also removed profile_task_exit(), which may
prevent third-party kernel modules from detecting process exits timely.
Add the new trace_sched_profile_task_exit() this way a user-space monitor
could detect the exits and potentially make some preparations in advance.
Signed-off-by: Wen Yang <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
---
include/trace/events/sched.h | 28 ++++++++++++++++++++++++++++
kernel/exit.c | 1 +
2 files changed, 29 insertions(+)
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index dbb01b4b7451..750b2f0bdf69 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -341,6 +341,34 @@ DEFINE_EVENT(sched_process_template, sched_wait_task,
TP_PROTO(struct task_struct *p),
TP_ARGS(p));
+/*
+ * Tracepoint for profiling a task that is starting to exit:
+ */
+TRACE_EVENT(sched_profile_task_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 a waiting task:
*/
diff --git a/kernel/exit.c b/kernel/exit.c
index 493647fd7c07..f675f879a1b2 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_profile_task_exit(tsk, code);
kcov_task_exit(tsk);
kmsan_task_exit(tsk);
--
2.25.1
On 2024-02-22 11:04, [email protected] wrote:
> From: Wen Yang <[email protected]>
>
> 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.
>
> Commit 2d4bcf886e42 ("exit: Remove profile_task_exit & profile_munmap")
> simplified the code, but also removed profile_task_exit(), which may
> prevent third-party kernel modules from detecting process exits timely.
>
> Add the new trace_sched_profile_task_exit() this way a user-space monitor
> could detect the exits and potentially make some preparations in advance.
I don't see any explanation justifying adding an extra tracepoint
rather than just moving trace_sched_process_exit() earlier in do_exit().
Why is moving trace_sched_process_exit() earlier in do_exit() an issue,
considering that any tracer interested in knowing the point where a task
is really reclaimed (from zombie state) is trace_sched_process_free()
called from delayed_put_task_struct() ?
Thanks,
Mathieu
>
> Signed-off-by: Wen Yang <[email protected]>
> Cc: Oleg Nesterov <[email protected]>
> Cc: Steven Rostedt <[email protected]>
> Cc: Masami Hiramatsu <[email protected]>
> Cc: Mathieu Desnoyers <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: Mel Gorman <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: [email protected]
> ---
> include/trace/events/sched.h | 28 ++++++++++++++++++++++++++++
> kernel/exit.c | 1 +
> 2 files changed, 29 insertions(+)
>
> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
> index dbb01b4b7451..750b2f0bdf69 100644
> --- a/include/trace/events/sched.h
> +++ b/include/trace/events/sched.h
> @@ -341,6 +341,34 @@ DEFINE_EVENT(sched_process_template, sched_wait_task,
> TP_PROTO(struct task_struct *p),
> TP_ARGS(p));
>
> +/*
> + * Tracepoint for profiling a task that is starting to exit:
> + */
> +TRACE_EVENT(sched_profile_task_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 a waiting task:
> */
> diff --git a/kernel/exit.c b/kernel/exit.c
> index 493647fd7c07..f675f879a1b2 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_profile_task_exit(tsk, code);
> kcov_task_exit(tsk);
> kmsan_task_exit(tsk);
>
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
On 2024/2/23 00:25, Mathieu Desnoyers wrote:
> On 2024-02-22 11:04, [email protected] wrote:
>> From: Wen Yang <[email protected]>
>>
>> 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.
>>
>> Commit 2d4bcf886e42 ("exit: Remove profile_task_exit & profile_munmap")
>> simplified the code, but also removed profile_task_exit(), which may
>> prevent third-party kernel modules from detecting process exits timely.
>>
>> Add the new trace_sched_profile_task_exit() this way a user-space monitor
>> could detect the exits and potentially make some preparations in advance.
>
> I don't see any explanation justifying adding an extra tracepoint
> rather than just moving trace_sched_process_exit() earlier in do_exit().
>
> Why is moving trace_sched_process_exit() earlier in do_exit() an issue,
> considering that any tracer interested in knowing the point where a task
> is really reclaimed (from zombie state) is trace_sched_process_free()
> called from delayed_put_task_struct() ?
>
> Thanks,
>
> Mathieu
>
Thanks.
We will make the modifications according to your suggestions.
--
Best wishes,
Wen
>>
>> Signed-off-by: Wen Yang <[email protected]>
>> Cc: Oleg Nesterov <[email protected]>
>> Cc: Steven Rostedt <[email protected]>
>> Cc: Masami Hiramatsu <[email protected]>
>> Cc: Mathieu Desnoyers <[email protected]>
>> Cc: Ingo Molnar <[email protected]>
>> Cc: Mel Gorman <[email protected]>
>> Cc: Peter Zijlstra <[email protected]>
>> Cc: [email protected]
>> ---
>> include/trace/events/sched.h | 28 ++++++++++++++++++++++++++++
>> kernel/exit.c | 1 +
>> 2 files changed, 29 insertions(+)
>>
>> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
>> index dbb01b4b7451..750b2f0bdf69 100644
>> --- a/include/trace/events/sched.h
>> +++ b/include/trace/events/sched.h
>> @@ -341,6 +341,34 @@ DEFINE_EVENT(sched_process_template,
>> sched_wait_task,
>> TP_PROTO(struct task_struct *p),
>> TP_ARGS(p));
>> +/*
>> + * Tracepoint for profiling a task that is starting to exit:
>> + */
>> +TRACE_EVENT(sched_profile_task_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 a waiting task:
>> */
>> diff --git a/kernel/exit.c b/kernel/exit.c
>> index 493647fd7c07..f675f879a1b2 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_profile_task_exit(tsk, code);
>> kcov_task_exit(tsk);
>> kmsan_task_exit(tsk);
>