From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753772AbcFMSo0 (ORCPT ); Mon, 13 Jun 2016 14:44:26 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:43490 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161385AbcFMShd (ORCPT ); Mon, 13 Jun 2016 14:37:33 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Martin Schwidefsky" , "Heiko Carstens" Date: Mon, 13 Jun 2016 19:36:37 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 028/114] s390/spinlock: avoid yield to non existent cpu In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.36-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Heiko Carstens commit 8497695243f70fd19ed6cf28b63584f1b608b5f9 upstream. arch_spin_lock_wait_flags() checks if a spinlock is not held before trying a compare and swap instruction. If the lock is unlocked it tries the compare and swap instruction, however if a different cpu grabbed the lock in the meantime the instruction will fail as expected. Subsequently the arch_spin_lock_wait_flags() incorrectly tries to figure out if the cpu that holds the lock is running. However it is using the wrong cpu number for this (-1) and then will also yield the current cpu to the wrong cpu. Fix this by adding a missing continue statement. Fixes: 470ada6b1a1d ("s390/spinlock: refactor arch_spin_lock_wait[_flags]") Signed-off-by: Heiko Carstens Acked-by: Martin Schwidefsky Signed-off-by: Ben Hutchings --- arch/s390/lib/spinlock.c | 1 + 1 file changed, 1 insertion(+) --- a/arch/s390/lib/spinlock.c +++ b/arch/s390/lib/spinlock.c @@ -75,6 +75,7 @@ void arch_spin_lock_wait_flags(arch_spin if (_raw_compare_and_swap(&lp->lock, 0, cpu)) return; local_irq_restore(flags); + continue; } /* Check if the lock owner is running. */ if (!smp_vcpu_scheduled(~owner)) {