From owner-svn-src-all@freebsd.org Thu Dec 22 17:51:45 2016 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E9E23C8B93D; Thu, 22 Dec 2016 17:51:45 +0000 (UTC) (envelope-from markj@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::e6a:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id B9AE41742; Thu, 22 Dec 2016 17:51:45 +0000 (UTC) (envelope-from markj@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id uBMHpi1V062787; Thu, 22 Dec 2016 17:51:44 GMT (envelope-from markj@FreeBSD.org) Received: (from markj@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id uBMHpim4062786; Thu, 22 Dec 2016 17:51:44 GMT (envelope-from markj@FreeBSD.org) Message-Id: <201612221751.uBMHpim4062786@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: markj set sender to markj@FreeBSD.org using -f From: Mark Johnston Date: Thu, 22 Dec 2016 17:51:44 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r310423 - head/sys/kern X-SVN-Group: head MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 22 Dec 2016 17:51:46 -0000 Author: markj Date: Thu Dec 22 17:51:44 2016 New Revision: 310423 URL: https://svnweb.freebsd.org/changeset/base/310423 Log: Revert part of r300109. The removal of TAILQ_FOREACH_SAFE introduced a small race: when the last thread on a sleepqueue is awoken, it reclaims the sleepqueue and may begin executing on a different CPU before sleepq_resume_thread() returns. This leaves a window during which it may go back to sleep and incorrectly be awoken again by the caller of sleepq_broadcast(). Reported and tested by: pho MFC after: 3 days Sponsored by: Dell EMC Isilon Modified: head/sys/kern/subr_sleepqueue.c Modified: head/sys/kern/subr_sleepqueue.c ============================================================================== --- head/sys/kern/subr_sleepqueue.c Thu Dec 22 17:44:27 2016 (r310422) +++ head/sys/kern/subr_sleepqueue.c Thu Dec 22 17:51:44 2016 (r310423) @@ -880,7 +880,7 @@ int sleepq_broadcast(void *wchan, int flags, int pri, int queue) { struct sleepqueue *sq; - struct thread *td; + struct thread *td, *tdn; int wakeup_swapper; CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags); @@ -894,7 +894,7 @@ sleepq_broadcast(void *wchan, int flags, /* Resume all blocked threads on the sleep queue. */ wakeup_swapper = 0; - while ((td = TAILQ_FIRST(&sq->sq_blocked[queue])) != NULL) { + TAILQ_FOREACH_SAFE(td, &sq->sq_blocked[queue], td_slpq, tdn) { thread_lock(td); wakeup_swapper |= sleepq_resume_thread(sq, td, pri); thread_unlock(td);