From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 BDAED36F90F for ; Mon, 24 Aug 2026 16:31:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787589108; cv=none; b=IQlFCmD78e4vZ/DzCs+/RfggMCS0AaGpFCZKQbAxh8RDODHkLqGvws7NcdCv90qSfSwlqHwQ0Uh/pY9rGLNGLnGxmsl3eF+kEyXIKRlcWhktxtr3nQg23SMCiiP9OilwdwTBKLrEIMALmIvmLGBxjGK+yYNPpewF4pjE6/BCMUo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787589108; c=relaxed/simple; bh=s0t43LFobE993QI1wGJ5TadALadztGuTdp21rFhcSe0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=T2e6lD7hRQBuGX+byIIp/yDEg05scNm1EzJMee9bjZ2pLUA1+U5tdBVmTgAdQvp7Bq6fra7MSpfhL4eZPXGTgNZ9pjBCLKzhGOGDX8nNFfyezuyZs1A1o3xFHOlTScbEInS9izhPay9Z0mIHIccSgh2vnX26pa/K4pDt7QILhyc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HkPyl934; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HkPyl934" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B04EF1F000E9; Mon, 24 Aug 2026 16:31:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787589107; bh=SVY3azd3nX8YcsbQfkNlEyRIQxzSvTk5A/iFX4jCbhc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=HkPyl934Lwd0kGjNbU64QKPDXJJSpHyI47ota5Gj8F4kVx+G8wm6rdN3eCZr6jDcV jDLO2wcizbxv1DNXIhtZyhHEnvQcE84HwD8DhhLCr//KjXB3StKqXNBm4Z7GsR9lPq H6214libouTYuPVOv95rK38V3798beX7ZFsBA5/embQByFS5MQDP6N0I/GfdDkleUK xglzUN+/6MlGsq7Fh2j8NUdDwYqaeSjnWWPdVP9w9AHGnegTG8jeUrknXg2M2H9Png TMbeXNQiV554zl96yYDb9uMFLRyIIH0yIwUGTS5Ourobum9e8FhG0Cu1UivohZKLOC tWU7YN950NtCg== Date: Mon, 24 Aug 2026 18:31:44 +0200 From: Frederic Weisbecker To: Thomas Gleixner Cc: Hyunwoo Kim , oleg@redhat.com, brauner@kernel.org, peterz@infradead.org, anna-maria@linutronix.de, ebiederm@xmission.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] signal: Use list_del_init_careful() in flush_sigqueue() Message-ID: References: <875x10hrkt.ffs@fw13> <8733w3j1i1.ffs@fw13> 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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8733w3j1i1.ffs@fw13> Le Mon, Aug 24, 2026 at 11:45:10AM +0200, Thomas Gleixner a écrit : > On Mon, Aug 24 2026 at 10:04, Thomas Gleixner wrote: > > > On Sat, Aug 22 2026 at 14:37, Hyunwoo Kim wrote: > >> diff --git a/kernel/signal.c b/kernel/signal.c > >> index bbc0fd4cc4d7c1..ec9a0a0490d19f 100644 > >> --- a/kernel/signal.c > >> +++ b/kernel/signal.c > >> @@ -482,7 +482,11 @@ void flush_sigqueue(struct sigpending *queue) > >> sigemptyset(&queue->signal); > >> while (!list_empty(&queue->list)) { > >> q = list_entry(queue->list.next, struct sigqueue , list); > >> - list_del_init(&q->list); > >> + /* > >> + * Pairs with the list_empty() in posixtimer_send_sigqueue(). > > > > No. That list_empty() would need to be changed to list_empty_careful() > > to be correct on weakly ordered architectures. > > > > Aside of that I'm not convinced that this is the right way to handle > > this as it cures the symptom and not the underlying problem. Let me > > stare at this some more. > > Something like the untested below. > > Thanks, > > tglx > --- > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -983,6 +983,18 @@ static int de_thread(struct task_struct > } > > /* > + * Ensure that POSIX timer SIGEV_THREAD_ID signals pending for > + * the former leader are removed under sighand::siglock _before_ > + * taking over the leader's TID. Otherwise the lockless cleanup > + * in release_task() can race against a concurrent signal > + * delivery to the new leader. The former leader has PF_EXITING > + * set which prevents queueing of SIGEV_THREAD_ID signals up to > + * the point where it's sighand gets cleared. > + */ > + scoped_guard(spinlock_irq, lock) > + flush_sigqueue(&leader->pending); > + > + /* > * The only record we have of the real-time age of a > * process, regardless of execs it's done, is start_time. > * All the past CPU time is accumulated in signal_struct > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -1998,6 +1998,13 @@ void posixtimer_send_sigqueue(struct k_i > return; > > /* > + * If the signal is targeted at a specific thread, validate with sighand > + * lock held that the thread is not exiting. > + */ > + if (unlikely(tmr->it_pid_type == PIDTYPE_PID && t->flags & PF_EXITING)) > + goto unlock; > + > + /* > * Update @tmr::sigqueue_seq for posix timer signals with sighand > * locked to prevent a race against dequeue_signal(). > */ > @@ -2088,6 +2095,7 @@ void posixtimer_send_sigqueue(struct k_i > result = TRACE_SIGNAL_DELIVERED; > out: > trace_signal_generate(sig, &q->info, t, tmr->it_pid_type != PIDTYPE_PID, result); > +unlock: > unlock_task_sighand(t, &flags); > } > This one looks good, FWIW. Thanks. -- Frederic Weisbecker SUSE Labs