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Date: Mon, 2 Dec 2024 11:30:35 +0100
From: "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
To: Siddh Raman Pant <siddh.raman.pant@oracle.com>
Cc: "sashal@kernel.org" <sashal@kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
	"shivani.agarwal@broadcom.com" <shivani.agarwal@broadcom.com>
Subject: Re: [PATCH 1/2] cgroup: Make operations on the cgroup root_list RCU
 safe
Message-ID: <2024120222-legwarmer-attach-896b@gregkh>
References: <2024120235-path-hangover-4717@gregkh>
 <20241202101102.91106-1-siddh.raman.pant@oracle.com>
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In-Reply-To: <9953011d972d0ec2f38792e985aac55f2e4fda2e.camel@oracle.com>

On Mon, Dec 02, 2024 at 10:26:54AM +0000, Siddh Raman Pant wrote:
> On Mon, Dec 02 2024 at 15:47:00 +0530, Greg Kroah-Hartman wrote:
> > On Mon, Dec 02, 2024 at 03:41:01PM +0530, Siddh Raman Pant wrote:
> > > From: Yafang Shao <laoar.shao@gmail.com>
> > > 
> > > commit d23b5c577715892c87533b13923306acc6243f93 upstream.
> > > 
> > > At present, when we perform operations on the cgroup root_list, we must
> > > hold the cgroup_mutex, which is a relatively heavyweight lock. In reality,
> > > we can make operations on this list RCU-safe, eliminating the need to hold
> > > the cgroup_mutex during traversal. Modifications to the list only occur in
> > > the cgroup root setup and destroy paths, which should be infrequent in a
> > > production environment. In contrast, traversal may occur frequently.
> > > Therefore, making it RCU-safe would be beneficial.
> > > 
> > > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > > Signed-off-by: Tejun Heo <tj@kernel.org>
> > > [fp: adapt to 5.10 mainly because of changes made by e210a89f5b07
> > >  ("cgroup.c: add helper __cset_cgroup_from_root to cleanup duplicated
> > >  codes")]
> > > Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
> > > [Shivani: Modified to apply on v5.4.y]
> > > Signed-off-by: Shivani Agarwal <shivani.agarwal@broadcom.com>
> > > Reviewed-by: Siddh Raman Pant <siddh.raman.pant@oracle.com>
> > 
> > I'm confused.  You do know what signed-off-by means, right?  When
> > sending a patch on, you MUST sign off on it.
> 
> Even if I'm just *forwarding* the patch already posted on the mailing
> list?

Yes.