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Date:      Thu, 23 Nov 2017 14:29:08 +0000 (UTC)
From:      Mark Johnston <markj@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r326134 - head/sys/cddl/contrib/opensolaris/uts/common/dtrace
Message-ID:  <201711231429.vANET8R2038484@repo.freebsd.org>

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Author: markj
Date: Thu Nov 23 14:29:07 2017
New Revision: 326134
URL: https://svnweb.freebsd.org/changeset/base/326134

Log:
  Duplicate helpers after disabling inherited tracepoints during a fork.
  
  We may create probes in the nascent child process, so we first need to
  ensure that any inherited tracepoints are first removed. Otherwise the
  probe sites will not be in the state expected by fasttrap, and it won't
  be able to enable the probes.
  
  MFC after:	2 weeks

Modified:
  head/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c

Modified: head/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c
==============================================================================
--- head/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c	Thu Nov 23 14:28:14 2017	(r326133)
+++ head/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c	Thu Nov 23 14:29:07 2017	(r326134)
@@ -601,8 +601,8 @@ fasttrap_fork(proc_t *p, proc_t *cp)
 	pid_t ppid = p->p_pid;
 	int i;
 
-#ifdef illumos
 	ASSERT(curproc == p);
+#ifdef illumos
 	ASSERT(p->p_proc_flag & P_PR_LOCK);
 #else
 	PROC_LOCK_ASSERT(p, MA_OWNED);
@@ -610,26 +610,15 @@ fasttrap_fork(proc_t *p, proc_t *cp)
 #ifdef illumos
 	ASSERT(p->p_dtrace_count > 0);
 #else
-	if (p->p_dtrace_helpers) {
-		/*
-		 * dtrace_helpers_duplicate() allocates memory.
-		 */
-		_PHOLD(cp);
-		PROC_UNLOCK(p);
-		PROC_UNLOCK(cp);
-		dtrace_helpers_duplicate(p, cp);
-		PROC_LOCK(cp);
-		PROC_LOCK(p);
-		_PRELE(cp);
-	}
 	/*
 	 * This check is purposely here instead of in kern_fork.c because,
 	 * for legal resons, we cannot include the dtrace_cddl.h header
 	 * inside kern_fork.c and insert if-clause there.
 	 */
-	if (p->p_dtrace_count == 0)
+	if (p->p_dtrace_count == 0 && p->p_dtrace_helpers == NULL)
 		return;
 #endif
+
 	ASSERT(cp->p_dtrace_count == 0);
 
 	/*
@@ -658,6 +647,8 @@ fasttrap_fork(proc_t *p, proc_t *cp)
 	_PHOLD(cp);
 	PROC_UNLOCK(cp);
 	PROC_UNLOCK(p);
+	if (p->p_dtrace_count == 0)
+		goto dup_helpers;
 #endif
 
 	/*
@@ -711,6 +702,9 @@ fasttrap_fork(proc_t *p, proc_t *cp)
 	mutex_enter(&cp->p_lock);
 	sprunlock(cp);
 #else
+dup_helpers:
+	if (p->p_dtrace_helpers != NULL)
+		dtrace_helpers_duplicate(p, cp);
 	PROC_LOCK(p);
 	PROC_LOCK(cp);
 	_PRELE(cp);



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