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Mon, 27 Jan 2020 09:15:02 -0800 (PST) From: Madhuparna Bhowmik X-Google-Original-From: Madhuparna Bhowmik Date: Mon, 27 Jan 2020 22:44:53 +0530 To: Oleg Nesterov Cc: madhuparnabhowmik10@gmail.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, ebiederm@xmission.com, christian.brauner@ubuntu.com, paulmck@kernel.org, joel@joelfernandes.org, linux-kernel@vger.kernel.org, linux-kernel-mentees@lists.linuxfoundation.org, frextrite@gmail.com, rcu@vger.kernel.org Subject: Re: [PATCH] sched.h: Annotate sighand_struct with __rcu Message-ID: <20200127171453.GA4002@madhuparna-HP-Notebook> References: <20200124045908.26389-1-madhuparnabhowmik10@gmail.com> <20200127092951.GA1116@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200127092951.GA1116@redhat.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 27, 2020 at 10:29:52AM +0100, Oleg Nesterov wrote: > On 01/24, madhuparnabhowmik10@gmail.com wrote: > > > > --- a/include/linux/sched.h > > +++ b/include/linux/sched.h > > @@ -918,7 +918,7 @@ struct task_struct { > > > > /* Signal handlers: */ > > struct signal_struct *signal; > > - struct sighand_struct *sighand; > > + struct sighand_struct __rcu *sighand; > > sigset_t blocked; > > sigset_t real_blocked; > > /* Restored if set_restore_sigmask() was used: */ > > diff --git a/kernel/signal.c b/kernel/signal.c > > index bcd46f547db3..9ad8dea93dbb 100644 > > --- a/kernel/signal.c > > +++ b/kernel/signal.c > > @@ -1383,7 +1383,7 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk, > > * must see ->sighand == NULL. > > */ > > spin_lock_irqsave(&sighand->siglock, *flags); > > - if (likely(sighand == tsk->sighand)) > > + if (likely(sighand == rcu_access_pointer(tsk->sighand))) > > break; > > spin_unlock_irqrestore(&sighand->siglock, *flags); > > } > > ACK, > > perhaps you can also cleanup copy_sighand(). rcu_assign_pointer() makes no > sense, we should either move it down or simply use RCU_INIT_POINTER(). > Sure, I will do it and send a patch soon. Thank you, Madhuparna > Oleg. >