From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932082Ab2ACWlf (ORCPT ); Tue, 3 Jan 2012 17:41:35 -0500 Received: from mail-gy0-f202.google.com ([209.85.160.202]:47986 "EHLO mail-gy0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756301Ab2ACWl0 (ORCPT ); Tue, 3 Jan 2012 17:41:26 -0500 From: Mandeep Singh Baines To: linux-kernel@vger.kernel.org, Linus Torvalds Cc: Mandeep Singh Baines , Linus Torvalds , Ingo Molnar , Peter Zijlstra , Andrew Morton , John Kacur Subject: [PATCH] hung_task: fix false positive during vfork Date: Tue, 3 Jan 2012 14:41:13 -0800 Message-Id: <1325630473-27477-1-git-send-email-msb@chromium.org> X-Mailer: git-send-email 1.7.3.1 In-Reply-To: <1325344394.28904.43.camel@lappy> References: <1325344394.28904.43.camel@lappy> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org vfork parent uninterruptibly and unkillably waits for its child to exec/exit. This wait is of unbounded length. Ignore such waits in the hung_task detector. Signed-off-by: Mandeep Singh Baines Reported-by: Sasha Levin LKML-Reference: <1325344394.28904.43.camel@lappy> Cc: Linus Torvalds Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Andrew Morton Cc: John Kacur --- kernel/hung_task.c | 14 ++++++++++---- 1 files changed, 10 insertions(+), 4 deletions(-) diff --git a/kernel/hung_task.c b/kernel/hung_task.c index 8b1748d..2e48ec0 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -74,11 +74,17 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) /* * Ensure the task is not frozen. - * Also, when a freshly created task is scheduled once, changes - * its state to TASK_UNINTERRUPTIBLE without having ever been - * switched out once, it musn't be checked. + * Also, skip vfork and any other user process that freezer should skip. */ - if (unlikely(t->flags & PF_FROZEN || !switch_count)) + if (unlikely(t->flags & (PF_FROZEN | PF_FREEZER_SKIP))) + return; + + /* + * When a freshly created task is scheduled once, changes its state to + * TASK_UNINTERRUPTIBLE without having ever been switched out once, it + * musn't be checked. + */ + if (unlikely(!switch_count)) return; if (switch_count != t->last_switch_count) { -- 1.7.3.1