Date: Wed, 10 Aug 2016 15:25:45 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r303922 - head/sys/kern Message-ID: <201608101525.u7AFPjdH016021@repo.freebsd.org>
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Author: mjg Date: Wed Aug 10 15:25:44 2016 New Revision: 303922 URL: https://svnweb.freebsd.org/changeset/base/303922 Log: ktrace: do a lockless check on fork to see if tracing is enabled This saves 2 lock acquisitions in the common case. Modified: head/sys/kern/kern_ktrace.c Modified: head/sys/kern/kern_ktrace.c ============================================================================== --- head/sys/kern/kern_ktrace.c Wed Aug 10 15:24:15 2016 (r303921) +++ head/sys/kern/kern_ktrace.c Wed Aug 10 15:25:44 2016 (r303922) @@ -572,9 +572,14 @@ void ktrprocfork(struct proc *p1, struct proc *p2) { + MPASS(p2->p_tracevp == NULL); + MPASS(p2->p_traceflag == 0); + + if (p1->p_traceflag == 0) + return; + PROC_LOCK(p1); mtx_lock(&ktrace_mtx); - KASSERT(p2->p_tracevp == NULL, ("new process has a ktrace vnode")); if (p1->p_traceflag & KTRFAC_INHERIT) { p2->p_traceflag = p1->p_traceflag; if ((p2->p_tracevp = p1->p_tracevp) != NULL) {
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