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 3944638F83; Mon, 11 Nov 2024 21:54:33 +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=1731362074; cv=none; b=Em8kqOo11c5HoUkkiKMp1Y59zUPQ+YEGzQTzUhs6iKTGHjyOuCLYWyDOEkJmtUjpNHIBKPHsq31bn25RDzVWSh8BnnscHA83fu8E2ejXCx2nZ09Y9YSs9IYZEijcEErM9wx8eB5Sw2fFv164YnU6EZ+FHZe9BHOVdNM2B52NK5s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731362074; c=relaxed/simple; bh=GeEOpknn2g8B/jcqak5KC6c+DyBxdoY4g1+LKLSK8I0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YWxppCJGYg5+MKraSAf6n++523sk9EcfcX7rVae3tV6CnKQrmFni1zUqSdYSSW1++tfFDBFibjaqmyxtDmocFirHojoMcT/PaNRcPIEzt+k1pI2cDYbKwKOjZqNFxfK4RZy5kL+QiTjkvsFZfkvGjY02Z7unipTnmG58unk92iQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=io5miDFT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="io5miDFT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3AB7CC4CECF; Mon, 11 Nov 2024 21:54:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1731362073; bh=GeEOpknn2g8B/jcqak5KC6c+DyBxdoY4g1+LKLSK8I0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=io5miDFTkppzvNl4mKUAy52FHdl44PjMSxklknmg9itmupyCWPRw1sgEne/qNT8gv YhhZ3xS1g7TvNrrfLchRk07NaRI9SZh1Brgn2m3nmRN/0jVZFomXxU+0mcaS7YCYJV D9pM3tbEGEARToRH9jx9zzA/BoD08OC33ZEiIUOVB2T2Ey4M7jFJCM9Ux6S28LhcyE stz/WzSNMT0lVUO+0nGQjMhtBLynj/Fo8pPDed+/dsrhcbUSj8UislQGx89+ilzLBO AC339qXXZXgbw34Go+NjYVAjc/HlIEYYsNzjYX/GolCKOwgAucb3qc4C1bYYnCWabP KQPMKOiSeer8g== Date: Mon, 11 Nov 2024 22:54:30 +0100 From: Frederic Weisbecker To: Greg KH 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: References: <20241106021416.184155-1-sashal@kernel.org> <2024110957-anaconda-papaya-2f0a@gregkh> 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: <2024110957-anaconda-papaya-2f0a@gregkh> Hi Greg, Le Sat, Nov 09, 2024 at 03:54:09PM +0100, Greg KH a écrit : > 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? b5413156bad9 (posix-cpu-timers: Clear TICK_DEP_BIT_POSIX_TIMER on clone) Thanks. > > thanks, > > greg k-h