From owner-svn-src-all@FreeBSD.ORG Fri May 6 14:05:33 2011 Return-Path: Delivered-To: svn-src-all@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6068A106564A; Fri, 6 May 2011 14:05:33 +0000 (UTC) (envelope-from fabient@FreeBSD.org) Received: from svn.freebsd.org (svn.freebsd.org [IPv6:2001:4f8:fff6::2c]) by mx1.freebsd.org (Postfix) with ESMTP id 356E58FC0A; Fri, 6 May 2011 14:05:33 +0000 (UTC) Received: from svn.freebsd.org (localhost [127.0.0.1]) by svn.freebsd.org (8.14.4/8.14.4) with ESMTP id p46E5Xxt051240; Fri, 6 May 2011 14:05:33 GMT (envelope-from fabient@svn.freebsd.org) Received: (from fabient@localhost) by svn.freebsd.org (8.14.4/8.14.4/Submit) id p46E5XXW051237; Fri, 6 May 2011 14:05:33 GMT (envelope-from fabient@svn.freebsd.org) Message-Id: <201105061405.p46E5XXW051237@svn.freebsd.org> From: Fabien Thomas Date: Fri, 6 May 2011 14:05:33 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-8@freebsd.org X-SVN-Group: stable-8 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Cc: Subject: svn commit: r221528 - stable/8/sys/kern X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.5 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: Fri, 06 May 2011 14:05:33 -0000 Author: fabient Date: Fri May 6 14:05:32 2011 New Revision: 221528 URL: http://svn.freebsd.org/changeset/base/221528 Log: MFC r220198: Clearing the flag when preempting will let the preempted thread run too much time. This can finish in a scheduler deadlock with ping-pong between two threads. One sample of this is: - device lapic (to have a preemption point on critical_exit()) - options DEVICE_POLLING with HZ>1499 (to have lapic freq = hardclock freq) - running a cpu intensive task (that does not enter the kernel) - only one CPU on SMP or no SMP. As requested by jhb@ 4BSD have received the same type of fix instead of propagating the flag to the new thread. Modified: stable/8/sys/kern/sched_4bsd.c stable/8/sys/kern/sched_ule.c Directory Properties: stable/8/sys/ (props changed) stable/8/sys/amd64/include/xen/ (props changed) stable/8/sys/cddl/contrib/opensolaris/ (props changed) stable/8/sys/contrib/dev/acpica/ (props changed) stable/8/sys/contrib/pf/ (props changed) Modified: stable/8/sys/kern/sched_4bsd.c ============================================================================== --- stable/8/sys/kern/sched_4bsd.c Fri May 6 13:51:54 2011 (r221527) +++ stable/8/sys/kern/sched_4bsd.c Fri May 6 14:05:32 2011 (r221528) @@ -944,13 +944,9 @@ sched_switch(struct thread *td, struct t if ((td->td_flags & TDF_NOLOAD) == 0) sched_load_rem(); - if (newtd) { - MPASS(newtd->td_lock == &sched_lock); - newtd->td_flags |= (td->td_flags & TDF_NEEDRESCHED); - } - td->td_lastcpu = td->td_oncpu; - td->td_flags &= ~TDF_NEEDRESCHED; + if (!(flags & SW_PREEMPT)) + td->td_flags &= ~TDF_NEEDRESCHED; td->td_owepreempt = 0; td->td_oncpu = NOCPU; Modified: stable/8/sys/kern/sched_ule.c ============================================================================== --- stable/8/sys/kern/sched_ule.c Fri May 6 13:51:54 2011 (r221527) +++ stable/8/sys/kern/sched_ule.c Fri May 6 14:05:32 2011 (r221528) @@ -1795,7 +1795,8 @@ sched_switch(struct thread *td, struct t ts->ts_rltick = ticks; td->td_lastcpu = td->td_oncpu; td->td_oncpu = NOCPU; - td->td_flags &= ~TDF_NEEDRESCHED; + if (!(flags & SW_PREEMPT)) + td->td_flags &= ~TDF_NEEDRESCHED; td->td_owepreempt = 0; tdq->tdq_switchcnt++; /*