Avoid panic when tearing down the DTrace pid provider for a

process that has crashed.

sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c:
	In fasttrap_pid_disable(), we cannot PHOLD the proc
	structure for a process that no longer exists, but
	we still have other, fasttrap specific, state that
	must be cleaned up for probes that existed in the
	dead process.  Instead of returning early if the
	process related to our probes isn't found,
	conditionalize the locking and carry on with a NULL
	proc pointer.  The rest of the fasttrap code already
	understands that a NULL proc is possible and does
	the right things in this case.

Sponsored by:	Spectra Logic Corporation
Reviewed by:	rpaulo, gnn
MFC after:	1 week

1 files changed, 6 insertions, 7 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c b/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c
index 4599a32..ad3b2d5 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c
@@ -1124,14 +1124,12 @@ fasttrap_pid_disable(void *arg, dtrace_id_t id, void *parg)
 	 * provider lock as a point of mutual exclusion to prevent other
 	 * DTrace consumers from disabling this probe.
 	 */
-	if ((p = pfind(probe->ftp_pid)) == NULL) {
-		mutex_exit(&provider->ftp_mtx);
-		return;
-	}
+	if ((p = pfind(probe->ftp_pid)) != NULL) {
 #ifdef __FreeBSD__
-	_PHOLD(p);
-	PROC_UNLOCK(p);
+		_PHOLD(p);
+		PROC_UNLOCK(p);
 #endif
+	}
 
 	/*
 	 * Disable all the associated tracepoints (for fully enabled probes).
@@ -1168,7 +1166,8 @@ fasttrap_pid_disable(void *arg, dtrace_id_t id, void *parg)
 		fasttrap_pid_cleanup();
 
 #ifdef __FreeBSD__
-	PRELE(p);
+	if (p != NULL)
+		PRELE(p);
 #endif
 	if (!probe->ftp_enabled)
 		return;