From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 B1BBB1E4B2; Sat, 9 Nov 2024 14:54:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731164054; cv=none; b=rMfm0LUqECEp3ckgthMKTv0KzHl17s/SyICa/QsJGLobL1RI/2XzDl4yy4Vqhts7XfnVQSVErvAYbf2phy03WyfZkFr7YVv1AGwvp+aaCezSAS2O6rClDfH7SATFO6p4vUBF79jR+VhZAx5WmEHBGiOOj6FpqFky3vgjJAfm6ec= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731164054; c=relaxed/simple; bh=wIzwSHJaB0B/G/7q4P5Ri7GUMQc2eTFEc5Hx8l1HXVg=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=mc8VUmGfGkKRLzQW4RnCLXi/EmZipbHplh4K8vfwWFy3PYWK5F/E9uuTyBULf4RhU40L1vSpEq1nwNow/Ug3ro/500vjViO25mrMMSyQ5ZD2Ba1r9Ixx4QH+IdeChht40hVMWpVleTcRyMpxSEKGlSUeeywHEXhPbLs3b7NsEH0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=1kGlzBDF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="1kGlzBDF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 94B6FC4CECE; Sat, 9 Nov 2024 14:54:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1731164053; bh=wIzwSHJaB0B/G/7q4P5Ri7GUMQc2eTFEc5Hx8l1HXVg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=1kGlzBDFb/Cktyk88KTzHuHdG0LJzJQHhEdE6KBoEFMwDTpv+GMcTxVJsG10RN2kx WqSvr0JVyOktoGZYG967QqBxbeEZ0kvWvGCdClFOGp2rmkm4Eh1IV0jece2oESo+NI 9XqcE0ixz03YU5f6ngpbGLL0V8Q2OAczT59AwVQs= Date: Sat, 9 Nov 2024 15:54:09 +0100 From: Greg KH To: Frederic Weisbecker Cc: Sasha Levin , stable@vger.kernel.org, bsegall@google.com, Thomas Gleixner , linux-kernel@vger.kernel.org Subject: Re: FAILED: Patch "posix-cpu-timers: Clear TICK_DEP_BIT_POSIX_TIMER on clone" failed to apply to v4.19-stable tree Message-ID: <2024110957-anaconda-papaya-2f0a@gregkh> References: <20241106021416.184155-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@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: On Thu, Nov 07, 2024 at 11:23:24AM +0100, Frederic Weisbecker wrote: > Le Tue, Nov 05, 2024 at 09:14:15PM -0500, Sasha Levin a écrit : > > The patch below does not apply to the v4.19-stable tree. > > If someone wants it applied there, or to any other stable or longterm > > tree, then please email the backport, including the original git commit > > id to . > > > > Thanks, > > Sasha > > Please try this: > > --- > >From ee0d95090203b7ee4cb1f29c586cd7d0dbf79fff Mon Sep 17 00:00:00 2001 > From: Benjamin Segall > Date: Fri, 25 Oct 2024 18:35:35 -0700 > Subject: [PATCH] posix-cpu-timers: Clear TICK_DEP_BIT_POSIX_TIMER on clone > > When cloning a new thread, its posix_cputimers are not inherited, and > are cleared by posix_cputimers_init(). However, this does not clear the > tick dependency it creates in tsk->tick_dep_mask, and the handler does > not reach the code to clear the dependency if there were no timers to > begin with. > > Thus if a thread has a cputimer running before clone/fork, all > descendants will prevent nohz_full unless they create a cputimer of > their own. > > Fix this by entirely clearing the tick_dep_mask in copy_process(). > (There is currently no inherited state that needs a tick dependency) > > Process-wide timers do not have this problem because fork does not copy > signal_struct as a baseline, it creates one from scratch. > > Fixes: b78783000d5c ("posix-cpu-timers: Migrate to use new tick dependency mask model") > Signed-off-by: Ben Segall > Signed-off-by: Thomas Gleixner > Reviewed-by: Frederic Weisbecker > Cc: stable@vger.kernel.org > Link: https://lore.kernel.org/all/xm26o737bq8o.fsf@google.com > --- > include/linux/tick.h | 8 ++++++++ > kernel/fork.c | 2 ++ > 2 files changed, 10 insertions(+) > > diff --git a/include/linux/tick.h b/include/linux/tick.h > index 443726085f6c..832381b812c2 100644 > --- a/include/linux/tick.h > +++ b/include/linux/tick.h > @@ -233,12 +233,19 @@ static inline void tick_dep_set_task(struct task_struct *tsk, > if (tick_nohz_full_enabled()) > tick_nohz_dep_set_task(tsk, bit); > } > + > static inline void tick_dep_clear_task(struct task_struct *tsk, > enum tick_dep_bits bit) > { > if (tick_nohz_full_enabled()) > tick_nohz_dep_clear_task(tsk, bit); > } > + > +static inline void tick_dep_init_task(struct task_struct *tsk) > +{ > + atomic_set(&tsk->tick_dep_mask, 0); > +} > + > static inline void tick_dep_set_signal(struct signal_struct *signal, > enum tick_dep_bits bit) > { > @@ -272,6 +279,7 @@ static inline void tick_dep_set_task(struct task_struct *tsk, > enum tick_dep_bits bit) { } > static inline void tick_dep_clear_task(struct task_struct *tsk, > enum tick_dep_bits bit) { } > +static inline void tick_dep_init_task(struct task_struct *tsk) { } > static inline void tick_dep_set_signal(struct signal_struct *signal, > enum tick_dep_bits bit) { } > static inline void tick_dep_clear_signal(struct signal_struct *signal, > diff --git a/kernel/fork.c b/kernel/fork.c > index b65871600507..1fb06d8952bc 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -91,6 +91,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -1829,6 +1830,7 @@ static __latent_entropy struct task_struct *copy_process( > acct_clear_integrals(p); > > posix_cpu_timers_init(p); > + tick_dep_init_task(p); > > p->io_context = NULL; > audit_set_context(p, NULL); > -- > 2.46.0 > > What is the git id of this in Linus's tree? thanks, greg k-h