Author: gibbs
Date: Wed Feb 20 17:55:17 2013
New Revision: 247049
URL: http://svnweb.freebsd.org/changeset/base/247049

Log:
  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

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      Wed Feb 
20 17:46:38 2013        (r247048)
+++ head/sys/cddl/contrib/opensolaris/uts/common/dtrace/fasttrap.c      Wed Feb 
20 17:55:17 2013        (r247049)
@@ -1124,14 +1124,12 @@ fasttrap_pid_disable(void *arg, dtrace_i
         * 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_i
                fasttrap_pid_cleanup();
 
 #ifdef __FreeBSD__
-       PRELE(p);
+       if (p != NULL)
+               PRELE(p);
 #endif
        if (!probe->ftp_enabled)
                return;
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