From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f179.google.com (mail-ob0-f179.google.com [209.85.214.179]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority" (not verified)) by ozlabs.org (Postfix) with ESMTPS id A879CB705D for ; Mon, 23 Apr 2012 17:11:00 +1000 (EST) Received: by mail-ob0-f179.google.com with SMTP id uo19so7505922obb.38 for ; Mon, 23 Apr 2012 00:11:00 -0700 (PDT) Date: Mon, 23 Apr 2012 00:09:43 -0700 From: Anton Vorontsov To: Andrew Morton , Oleg Nesterov Subject: [PATCH 9/9] um: Properly check all process' threads for a live mm Message-ID: <20120423070943.GI30752@lizard> References: <20120423070641.GA27702@lizard> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: <20120423070641.GA27702@lizard> Cc: linaro-kernel@lists.linaro.org, Mike Frysinger , Peter Zijlstra , user-mode-linux-devel@lists.sourceforge.net, linux-sh@vger.kernel.org, Richard Weinberger , patches@linaro.org, linux-kernel@vger.kernel.org, uclinux-dist-devel@blackfin.uclinux.org, linux-mm@kvack.org, Paul Mundt , John Stultz , KOSAKI Motohiro , Russell King , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , kill_off_processes() might miss a valid process, this is because checking for process->mm is not enough. Process' main thread may exit or detach its mm via use_mm(), but other threads may still have a valid mm. To catch this we use find_lock_task_mm(), which walks up all threads and returns an appropriate task (with task lock held). Suggested-by: Oleg Nesterov Signed-off-by: Anton Vorontsov --- arch/um/kernel/reboot.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/um/kernel/reboot.c b/arch/um/kernel/reboot.c index 1411f4e..3d15243 100644 --- a/arch/um/kernel/reboot.c +++ b/arch/um/kernel/reboot.c @@ -6,6 +6,7 @@ #include "linux/sched.h" #include "linux/spinlock.h" #include "linux/slab.h" +#include "linux/oom.h" #include "kern_util.h" #include "os.h" #include "skas.h" @@ -25,13 +26,13 @@ static void kill_off_processes(void) read_lock(&tasklist_lock); for_each_process(p) { - task_lock(p); - if (!p->mm) { - task_unlock(p); + struct task_struct *t; + + t = find_lock_task_mm(p); + if (!t) continue; - } - pid = p->mm->context.id.u.pid; - task_unlock(p); + pid = t->mm->context.id.u.pid; + task_unlock(t); os_kill_ptraced_process(pid, 1); } read_unlock(&tasklist_lock); -- 1.7.9.2