Author: fabient
Date: Tue Apr  3 07:48:58 2012
New Revision: 233825
URL: http://svn.freebsd.org/changeset/base/233825

Log:
  MFC r233544:
  Fix random deadlock on pmcstat exit:
  - Exit the thread when soft shutdown is requested
  - Wakeup owner thread.
  
  Reproduced/tested by looping pmcstat measurement:
  pmcstat -S instructions -O/tmp/test ls

Modified:
  stable/8/sys/dev/hwpmc/hwpmc_logging.c
Directory Properties:
  stable/8/sys/   (props changed)

Modified: stable/8/sys/dev/hwpmc/hwpmc_logging.c
==============================================================================
--- stable/8/sys/dev/hwpmc/hwpmc_logging.c      Tue Apr  3 07:15:42 2012        
(r233824)
+++ stable/8/sys/dev/hwpmc/hwpmc_logging.c      Tue Apr  3 07:48:58 2012        
(r233825)
@@ -284,6 +284,7 @@ pmclog_loop(void *arg)
                        if ((lb = TAILQ_FIRST(&po->po_logbuffers)) == NULL) {
                                mtx_unlock_spin(&po->po_mtx);
 
+                               /* No more buffers and shutdown required. */
                                if (po->po_flags & PMC_PO_SHUTDOWN) {
                                        mtx_unlock(&pmc_kthread_mtx);
                                        /*
@@ -292,6 +293,7 @@ pmclog_loop(void *arg)
                                         */
                                        fo_close(po->po_file, curthread);
                                        mtx_lock(&pmc_kthread_mtx);
+                                       break;
                                }
 
                                (void) msleep(po, &pmc_kthread_mtx, PWAIT,
@@ -354,6 +356,7 @@ pmclog_loop(void *arg)
                lb = NULL;
        }
 
+       wakeup_one(po->po_kthread);
        po->po_kthread = NULL;
 
        mtx_unlock(&pmc_kthread_mtx);
@@ -652,8 +655,7 @@ pmclog_deconfigure_log(struct pmc_owner 
            ("[pmclog,%d] po=%p no log file", __LINE__, po));
 
        /* stop the kthread, this will reset the 'OWNS_LOGFILE' flag */
-       if (po->po_kthread)
-               pmclog_stop_kthread(po);
+       pmclog_stop_kthread(po);
 
        KASSERT(po->po_kthread == NULL,
            ("[pmclog,%d] po=%p kthread not stopped", __LINE__, po));
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