From owner-svn-src-head@freebsd.org Mon Feb 19 00:54:09 2018 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 80F5DF16BC5; Mon, 19 Feb 2018 00:54:09 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from mxrelay.nyi.freebsd.org (mxrelay.nyi.freebsd.org [IPv6:2610:1c1:1:606c::19:3]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mxrelay.nyi.freebsd.org", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 36FDB76030; Mon, 19 Feb 2018 00:54:09 +0000 (UTC) (envelope-from mjg@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 31FA613945; Mon, 19 Feb 2018 00:54:09 +0000 (UTC) (envelope-from mjg@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id w1J0s9h6000152; Mon, 19 Feb 2018 00:54:09 GMT (envelope-from mjg@FreeBSD.org) Received: (from mjg@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id w1J0s9gd000151; Mon, 19 Feb 2018 00:54:09 GMT (envelope-from mjg@FreeBSD.org) Message-Id: <201802190054.w1J0s9gd000151@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: mjg set sender to mjg@FreeBSD.org using -f From: Mateusz Guzik Date: Mon, 19 Feb 2018 00:54:09 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r329542 - head/sys/kern X-SVN-Group: head X-SVN-Commit-Author: mjg X-SVN-Commit-Paths: head/sys/kern X-SVN-Commit-Revision: 329542 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: 2.1.25 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: Mon, 19 Feb 2018 00:54:09 -0000 Author: mjg Date: Mon Feb 19 00:54:08 2018 New Revision: 329542 URL: https://svnweb.freebsd.org/changeset/base/329542 Log: Fix process exit vs reap race introduced in r329449 The race manifested itself mostly in terms of crashes with "spin lock held too long". Relevant parts of respective code paths: exit: reap: PROC_LOCK(p); PROC_SLOCK(p); p->p_state == PRS_ZOMBIE PROC_UNLOCK(p); PROC_LOCK(p); /* exit work */ if (p->p_state == PRS_ZOMBIE) /* true */ proc_reap() free proc /* more exit work */ PROC_SUNLOCK(p); Thus a still exiting process is reaped. Prior to the change the zombie check was followed by slock/sunlock trip which prevented the problem. Even code prior to this commit has a bug: the proc is still accessed for statistic collection purposes. However, the severity is rather small and the bug may be fixed in a future commit. Reported by: many Tested by: allanjude Modified: head/sys/kern/kern_exit.c Modified: head/sys/kern/kern_exit.c ============================================================================== --- head/sys/kern/kern_exit.c Mon Feb 19 00:47:03 2018 (r329541) +++ head/sys/kern/kern_exit.c Mon Feb 19 00:54:08 2018 (r329542) @@ -819,6 +819,8 @@ proc_reap(struct thread *td, struct proc *p, int *stat PROC_LOCK_ASSERT(p, MA_OWNED); KASSERT(p->p_state == PRS_ZOMBIE, ("proc_reap: !PRS_ZOMBIE")); + mtx_spin_wait_unlocked(&p->p_slock); + q = td->td_proc; if (status)