From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 2B9313FCB3D; Fri, 18 Sep 2026 09:51:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789725064; cv=none; b=MyQS7GIzVAqaYg1sgJ/yRnrY3Tf4on60qSfnwZcIw9zfDLAewvFG0YoqKGZqrTUY+RsV7ELEkEUJb+hZhNWqc3Y2bev7b9Zw8q36SQHL1dBGITuQt8TpKS0dzM3rfbfpRBThUg3Y1p9hW1r8hHMz2FXTTEgl42LtIuxhAYgug7k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789725064; c=relaxed/simple; bh=ByCzBbmwZf/rDEK2PLyjRpdxLQzY2WfI/6eu3xdTqV0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FLNNN4e2x8SiSn7K++fX+/XV4KW7zP9DqQprOifCgZIbCAWFrqhzthZ2hnx54/foBwUqv0GnlpHLyIchmGSgZBJ9GSE0vQdpejQVcrmH0Zv8VaoLy4SXYEKRr/2BCnr2cG2Nh5tmkZMwBR2bJrF+Tz+IrQm7EQW+L07c3RyKc7o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=pass smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=KZ7gd8Y8; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="KZ7gd8Y8" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=noG7Xbw5qA6orJrsGAhv7ONYyvYhvezfCJLf3CU5i3g=; b=KZ7gd8Y88UOKHJhZOQ+EKpwhRJ 5qjc3vHidmfMQPObUKgqlTHKLEu81C4KJfG//Q4KEo1RHLBWvrb7zdnrnSqiVgiDY6dj1/zkFuSZ2 j+9QrpUw9a6VulXa++fkPhj1epOG+UEaNSG4e4QJTGBfzrvI6F/bj2qFBdilEBBmQtdQhZI2s631o fXOFIb81BPcDgBeAPtvtiAE0YgnuzYqmSbeiW84gymnPM0dPfRcC7lm03EUVCK5+pzvkMFD/GaaW4 pLWuI0K1iCnsUVq4J4QsIk/NzpneAYXyIDXjN+q3lvxxtgJFzaibVoveEWB1s4nO+41abBJANbrBn UaWBnfgA==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1x7VF4-0000000GkvP-0L5O; Fri, 18 Sep 2026 09:50:50 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 42EED300328; Fri, 18 Sep 2026 11:50:49 +0200 (CEST) Date: Fri, 18 Sep 2026 11:50:49 +0200 From: Peter Zijlstra To: Luo Gengkun Cc: mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, james.clark@linaro.org, elver@google.com, dvyukov@google.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf/core: Fix race between perf_event_exit_task and perf_pending_task Message-ID: <20260918095049.GL1837346@noisy.programming.kicks-ass.net> References: <20260416033443.1492483-1-luogengkun2@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260416033443.1492483-1-luogengkun2@huawei.com> On Thu, Apr 16, 2026 at 03:34:43AM +0000, Luo Gengkun wrote: > A race condition exists between perf_event_exit_task() and perf_pending_task(). > > During begin_new_exec(), perf_event_exit_task() may be called, and the > PF_EXITING flag is not set on task. so perf_sigtrap() continues to execute > and triggers WARN_ON_ONCE(event->ctx->task != current). > > To fix this problem, also check if the event->ctx->task is TASK_TOMBSTONE. > > Fixes: 97ba62b27867 ("perf: Add support for SIGTRAP on perf events") > Signed-off-by: Luo Gengkun > --- > kernel/events/core.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 1f5699b339ec..3422900263fa 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -7543,7 +7543,7 @@ static void perf_sigtrap(struct perf_event *event) > * Both perf_pending_task() and perf_pending_irq() can race with the > * task exiting. > */ > - if (current->flags & PF_EXITING) > + if (current->flags & PF_EXITING || event->ctx->task == TASK_TOMBSTONE) > return; Since do_exit() also calls perf_event_exit_task() (albeit a little later than exit_signals()), and task_can_queue_signal() will return false when PF_EXITING, and we ignore the return value of send_sig_perf()/send_sig_info(). I don't think we need to check both. That is, I think: if (event->ctx->task == TASK_TOMBSTONE) is sufficient. Also, the comment needs updating.