Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757612Ab2EGTE5 (ORCPT ); Mon, 7 May 2012 15:04:57 -0400 Received: from mga09.intel.com ([134.134.136.24]:44434 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757538Ab2EGTE4 (ORCPT ); Mon, 7 May 2012 15:04:56 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,351,1309762800"; d="scan'208";a="141079335" From: Suresh Siddha To: torvalds@linux-foundation.org, hpa@zytor.com, mingo@elte.hu, oleg@redhat.com Cc: suresh@aristanetworks.com, linux-kernel@vger.kernel.org, Suresh Siddha Subject: [PATCH 1/2] coredump: flush the fpu exit state for proper multi-threaded core dump Date: Mon, 7 May 2012 12:07:20 -0700 Message-Id: <1336417641-29771-1-git-send-email-suresh.b.siddha@intel.com> X-Mailer: git-send-email 1.7.6.5 In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2129 Lines: 62 Nalluru reported hitting the BUG_ON(__thread_has_fpu(tsk)) in arch/x86/kernel/xsave.c:__sanitize_i387_state() during the coredump of a multi-threaded application. A look at the exit seqeuence shows that other threads can still be on the runqueue potentially at the below shown exit_mm() code snippet: if (atomic_dec_and_test(&core_state->nr_threads)) complete(&core_state->startup); ===> other threads can still be active here, but we notify the thread ===> dumping core to wakeup from the coredump_wait() after the last thread ===> joins this point. Core dumping thread will continue dumping ===> all the threads state to the core file. for (;;) { set_task_state(tsk, TASK_UNINTERRUPTIBLE); if (!self.task) /* see coredump_finish() */ break; schedule(); } As some of those threads are on the runqueue and didn't call schedule() yet, their fpu state is still active in the live registers and the thread proceeding with the coredump will hit the above mentioned BUG_ON while trying to dump other threads fpustate to the coredump file. BUG_ON() in arch/x86/kernel/xsave.c:__sanitize_i387_state() is in the code paths for processors supporting xsaveopt. With or without xsaveopt, multi-threaded coredump is broken and maynot contain the correct fpustate at the time of exit. Fix this by explicitly flushing the fpu state in do_exit() by calling prepare_to_copy() Reported-by: Suresh Nalluru Signed-off-by: Suresh Siddha --- kernel/exit.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index d8bd3b42..913f2a6 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -974,6 +974,8 @@ void do_exit(long code) tty_audit_exit(); audit_free(tsk); + prepare_to_copy(tsk); + tsk->exit_code = code; taskstats_exit(tsk, group_dead); -- 1.7.6.5 -- 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/