Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761488AbZFLHLo (ORCPT ); Fri, 12 Jun 2009 03:11:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754390AbZFLHLh (ORCPT ); Fri, 12 Jun 2009 03:11:37 -0400 Received: from casper.infradead.org ([85.118.1.10]:48559 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752151AbZFLHLg (ORCPT ); Fri, 12 Jun 2009 03:11:36 -0400 Subject: Re: [PATCH 2/2] posix-cpu-timers: remove tasklist_lock where we can From: Peter Zijlstra To: Stanislaw Gruszka Cc: Thomas Gleixner , "linux-kernel@vger.kernel.org" , Oleg Nesterov , Ingo Molnar , Andrew Morton In-Reply-To: <20090612084927.11673956@dhcp-lab-109.englab.brq.redhat.com> References: <20090612084927.11673956@dhcp-lab-109.englab.brq.redhat.com> Content-Type: text/plain Date: Fri, 12 Jun 2009 09:11:17 +0200 Message-Id: <1244790677.6691.959.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1941 Lines: 59 On Fri, 2009-06-12 at 08:49 +0200, Stanislaw Gruszka wrote: > tasklist_lock is not needed to protect find_task_by_vpid() nor > thread_group_leader() nor same_thread_group() , use rcu_read_lock() instead. Aside from not being strictly needed, one can sometimes require a tasklist_lock reader to ensure nothing changes, however since the code is racy in that regard anyway, this looks good. Acked-by: Peter Zijlstra > Signed-off-by: Stanislaw Gruszka > --- > kernel/posix-cpu-timers.c | 8 ++++---- > 1 files changed, 4 insertions(+), 4 deletions(-) > > diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c > index bece7c0..1d9cdf3 100644 > --- a/kernel/posix-cpu-timers.c > +++ b/kernel/posix-cpu-timers.c > @@ -37,13 +37,13 @@ static int check_clock(const clockid_t which_clock) > if (pid == 0) > return 0; > > - read_lock(&tasklist_lock); > + rcu_read_lock(); > p = find_task_by_vpid(pid); > if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ? > same_thread_group(p, current) : thread_group_leader(p))) { > error = -EINVAL; > } > - read_unlock(&tasklist_lock); > + rcu_read_lock(); > > return error; > } > @@ -398,7 +398,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer) > new_timer->it.cpu.incr.sched = 0; > new_timer->it.cpu.expires.sched = 0; > > - read_lock(&tasklist_lock); > + rcu_read_lock(); > if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) { > if (pid == 0) { > p = current; > @@ -422,7 +422,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer) > } else { > ret = -EINVAL; > } > - read_unlock(&tasklist_lock); > + rcu_read_unlock(); > > return ret; > } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/