From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932799Ab2BCADv (ORCPT ); Thu, 2 Feb 2012 19:03:51 -0500 Received: from mail-bk0-f46.google.com ([209.85.214.46]:34921 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755214Ab2BCADu (ORCPT ); Thu, 2 Feb 2012 19:03:50 -0500 Date: Fri, 3 Feb 2012 04:03:45 +0400 From: Anton Vorontsov To: Greg KH , Oleg Nesterov Cc: Arve =?utf-8?B?SGrDuG5uZXbDpWc=?= , KOSAKI Motohiro , San Mehat , Colin Cross , "Eric W. Biederman" , linux-kernel@vger.kernel.org, kernel-team@android.com, linaro-kernel@lists.linaro.org, "Paul E. McKenney" Subject: [PATCH v3] staging: android/lowmemorykiller: Don't grab tasklist_lock Message-ID: <20120203000345.GA14338@oksana.dev.rtsoft.ru> References: <20120202171659.GA29378@oksana.dev.rtsoft.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20120202171659.GA29378@oksana.dev.rtsoft.ru> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Grabbing tasklist_lock has its disadvantages, i.e. it blocks process creation and destruction. If there are lots of processes, blocking doesn't sound as a great idea. For LMK, it is sufficient to surround tasks list traverse with rcu_read_{,un}lock(). >>From now on using force_sig() is not safe, as it can race with an already exiting task, so we use send_sig() now. As a downside, it won't kill PID namespace init processes, but that's not what we want anyway. Suggested-by: Oleg Nesterov Signed-off-by: Anton Vorontsov --- drivers/staging/android/lowmemorykiller.c | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c index 2d8d2b7..63da844 100644 --- a/drivers/staging/android/lowmemorykiller.c +++ b/drivers/staging/android/lowmemorykiller.c @@ -34,6 +34,7 @@ #include #include #include +#include #include #include @@ -132,7 +133,7 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc) } selected_oom_adj = min_adj; - read_lock(&tasklist_lock); + rcu_read_lock(); for_each_process(p) { struct mm_struct *mm; struct signal_struct *sig; @@ -180,12 +181,12 @@ static int lowmem_shrink(struct shrinker *s, struct shrink_control *sc) lowmem_deathpending = selected; task_handoff_register(&task_nb); #endif - force_sig(SIGKILL, selected); + send_sig(SIGKILL, selected, 0); rem -= selected_tasksize; } lowmem_print(4, "lowmem_shrink %lu, %x, return %d\n", sc->nr_to_scan, sc->gfp_mask, rem); - read_unlock(&tasklist_lock); + rcu_read_unlock(); return rem; } -- 1.7.7.6