From owner-svn-src-head@freebsd.org Thu Jan 23 03:36:51 2020 Return-Path: Delivered-To: svn-src-head@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 2EC6E22A70E; Thu, 23 Jan 2020 03:36:51 +0000 (UTC) (envelope-from jeff@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits) client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 4837HR0T6Jz3yRX; Thu, 23 Jan 2020 03:36:51 +0000 (UTC) (envelope-from jeff@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 mxrelay.nyi.freebsd.org (Postfix) with ESMTPS id 0B7A385EF; Thu, 23 Jan 2020 03:36:51 +0000 (UTC) (envelope-from jeff@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id 00N3aok0009273; Thu, 23 Jan 2020 03:36:50 GMT (envelope-from jeff@FreeBSD.org) Received: (from jeff@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id 00N3ao1X009272; Thu, 23 Jan 2020 03:36:50 GMT (envelope-from jeff@FreeBSD.org) Message-Id: <202001230336.00N3ao1X009272@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: jeff set sender to jeff@FreeBSD.org using -f From: Jeff Roberson Date: Thu, 23 Jan 2020 03:36:50 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r357014 - head/sys/kern X-SVN-Group: head X-SVN-Commit-Author: jeff X-SVN-Commit-Paths: head/sys/kern X-SVN-Commit-Revision: 357014 X-SVN-Commit-Repository: base MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 23 Jan 2020 03:36:51 -0000 Author: jeff Date: Thu Jan 23 03:36:50 2020 New Revision: 357014 URL: https://svnweb.freebsd.org/changeset/base/357014 Log: Block the thread lock in sched_throw() and use cpu_switch() to unblock it. The introduction of lockless switch in r355784 created a race to re-use the exiting thread that was only possible to hit on a hypervisor. Reported/Tested by: rlibby Discussed with: rlibby, jhb Modified: head/sys/kern/sched_ule.c Modified: head/sys/kern/sched_ule.c ============================================================================== --- head/sys/kern/sched_ule.c Thu Jan 23 01:49:22 2020 (r357013) +++ head/sys/kern/sched_ule.c Thu Jan 23 03:36:50 2020 (r357014) @@ -2894,7 +2894,7 @@ sched_throw(struct thread *td) struct thread *newtd; struct tdq *tdq; - if (td == NULL) { + if (__predict_false(td == NULL)) { #ifdef SMP PCPU_SET(sched, DPCPU_PTR(tdq)); #endif @@ -2912,13 +2912,18 @@ sched_throw(struct thread *td) tdq_load_rem(tdq, td); td->td_lastcpu = td->td_oncpu; td->td_oncpu = NOCPU; + thread_lock_block(td); } newtd = choosethread(); spinlock_enter(); TDQ_UNLOCK(tdq); KASSERT(curthread->td_md.md_spinlock_count == 1, ("invalid count %d", curthread->td_md.md_spinlock_count)); - cpu_throw(td, newtd); /* doesn't return */ + /* doesn't return */ + if (__predict_false(td == NULL)) + cpu_throw(td, newtd); /* doesn't return */ + else + cpu_switch(td, newtd, TDQ_LOCKPTR(tdq)); } /*