From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtpout.efficios.com (smtpout.efficios.com [167.114.26.122]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1C5A9151CF3 for ; Thu, 22 Feb 2024 16:25:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=167.114.26.122 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708619149; cv=none; b=NWvXW80lFWKdzWQ7ZYc+CGA1905OKcN3UDwtcbgcvpxDqIPQLcmNifSUI8ek2xXEyWFvfhbZP9obodGn/0Qcda61LFtDWGIasVzfy0e0O/vhJm4ToTl/6q9/BhATzsYiAlA3YHwp3+3SspY3CqIpgmBSPZB15w5/1azbvWsUZTc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708619149; c=relaxed/simple; bh=xI8c7R5FVGAN8wMc43qy4e84ldQjvtEyCbHUZkIpLIU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=EWadUo9FavauwqMcHA6zZdgDQisWEwIJQnOXVBThOi+WbrnvxrE5fshecBXDudQvw9lNNJFu111C9XI2NngzquXXkTg0Ae8Cta6HMd8TeZhQNMtcqPbXewAx8XGWnoPb8h29HyvID86joRiYVxZLWAA7PmBCMh9HbIcFZ5Y421g= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com; spf=pass smtp.mailfrom=efficios.com; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b=U380Pm1Q; arc=none smtp.client-ip=167.114.26.122 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=efficios.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.b="U380Pm1Q" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1708619137; bh=xI8c7R5FVGAN8wMc43qy4e84ldQjvtEyCbHUZkIpLIU=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=U380Pm1Q6KPMQNXOd51fT6xFpNJ2kPyBc5J9yYeWnOvCr8lexvxAozkD65j/w9CHw Z4BgxLFI7tuSISraqJtwhoA2LOod7y7By2eqFS/o8b5v/OO8MXHXpD3F+ocbWULJOD GQ99vF4e2dH5pN85X+PeKSlzKisaMCSO37xiCg5L0/aQqcT3XzqXPE+UG/UD9hCBfI D9YucIRUvZQFBLsv0v9JLrMLyh7vbVOhmjLqIeTYlA2Y3kuWKAGQwgjr95Xio0+M0b zKVgfUf8ouryxnIg71qbPaq5LzxSKtTjZuqvaXprYvqqcdWVbcQGjbNN07uRBR1ZpU TqACuGkL1BVhQ== Received: from [172.16.0.134] (192-222-143-198.qc.cable.ebox.net [192.222.143.198]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4TgdmK1WQKzdPk; Thu, 22 Feb 2024 11:25:37 -0500 (EST) Message-ID: Date: Thu, 22 Feb 2024 11:25:36 -0500 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] exit: add a tracepoint for profiling a task that is starting to exit Content-Language: en-US To: wenyang.linux@foxmail.com, Steven Rostedt , Masami Hiramatsu , Ingo Molnar Cc: Oleg Nesterov , Mel Gorman , Peter Zijlstra , linux-kernel@vger.kernel.org References: From: Mathieu Desnoyers In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2024-02-22 11:04, wenyang.linux@foxmail.com wrote: > From: Wen Yang > > 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 > Cc: Oleg Nesterov > Cc: Steven Rostedt > Cc: Masami Hiramatsu > Cc: Mathieu Desnoyers > Cc: Ingo Molnar > Cc: Mel Gorman > Cc: Peter Zijlstra > Cc: linux-kernel@vger.kernel.org > --- > 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