svn commit: r204878 - in head: sys/dev/hwpmc sys/sys usr.sbin/pmcstat

[Fabien Thomas]

Author: fabient
Date: Mon Mar  8 19:58:00 2010
New Revision: 204878
URL: http://svn.freebsd.org/changeset/base/204878

Log:
  Change the way shutdown is handled for log file.
  
  pmc_flush_logfile is now non-blocking and just ask the kernel
  to shutdown the file. From that point, no more data is
  accepted by the log thread and when the last buffer is flushed
  the file is closed.
  
  This will remove a deadlock between pmcstat asking for
  flush while it cannot flush the pipe itself.
  
  MFC after: 3 days

Modified:
  head/sys/dev/hwpmc/hwpmc_logging.c
  head/sys/sys/pmc.h
  head/usr.sbin/pmcstat/pmcstat_log.c

Modified: head/sys/dev/hwpmc/hwpmc_logging.c
==============================================================================
--- head/sys/dev/hwpmc/hwpmc_logging.c	Mon Mar  8 19:40:31 2010	(r204877)
+++ head/sys/dev/hwpmc/hwpmc_logging.c	Mon Mar  8 19:58:00 2010	(r204878)
@@ -237,7 +237,7 @@ pmclog_get_buffer(struct pmc_owner *po)
 static void
 pmclog_loop(void *arg)
 {
-	int error;
+	int error, last_buffer;
 	struct pmc_owner *po;
 	struct pmclog_buffer *lb;
 	struct proc *p;
@@ -252,6 +252,7 @@ pmclog_loop(void *arg)
 	p = po->po_owner;
 	td = curthread;
 	mycred = td->td_ucred;
+	last_buffer = 0;
 
 	PROC_LOCK(p);
 	ownercred = crhold(p->p_ucred);
@@ -284,27 +285,20 @@ pmclog_loop(void *arg)
 			if ((lb = TAILQ_FIRST(&po->po_logbuffers)) == NULL) {
 				mtx_unlock_spin(&po->po_mtx);
 
-				/*
-				 * Wakeup the thread waiting for the
-				 * PMC_OP_FLUSHLOG request to
-				 * complete.
-				 */
-				if (po->po_flags & PMC_PO_IN_FLUSH) {
-					po->po_flags &= ~PMC_PO_IN_FLUSH;
-					wakeup_one(po->po_kthread);
-				}
-
 				(void) msleep(po, &pmc_kthread_mtx, PWAIT,
 				    "pmcloop", 0);
 				continue;
 			}
 
 			TAILQ_REMOVE(&po->po_logbuffers, lb, plb_next);
+			if (po->po_flags & PMC_PO_SHUTDOWN)
+				last_buffer = TAILQ_EMPTY(&po->po_logbuffers);
 			mtx_unlock_spin(&po->po_mtx);
 		}
 
 		mtx_unlock(&pmc_kthread_mtx);
 
+sigpipe_retry:
 		/* process the request */
 		PMCDBG(LOG,WRI,2, "po=%p base=%p ptr=%p", po,
 		    lb->plb_base, lb->plb_ptr);
@@ -328,7 +322,8 @@ pmclog_loop(void *arg)
 
 		if (error) {
 			/* XXX some errors are recoverable */
-			/* XXX also check for SIGPIPE if a socket */
+			if (error == EPIPE)
+				goto sigpipe_retry;
 
 			/* send a SIGIO to the owner and exit */
 			PROC_LOCK(p);
@@ -344,6 +339,14 @@ pmclog_loop(void *arg)
 			break;
 		}
 
+		if (last_buffer) {
+			/*
+			 * Close the file to get PMCLOG_EOF error
+			 * in pmclog(3).
+			 */
+			fo_close(po->po_file, curthread);
+		}
+
 		mtx_lock(&pmc_kthread_mtx);
 
 		/* put the used buffer back into the global pool */
@@ -425,6 +428,12 @@ pmclog_reserve(struct pmc_owner *po, int
 
 	mtx_lock_spin(&po->po_mtx);
 
+	/* No more data when shutdown in progress. */
+	if (po->po_flags & PMC_PO_SHUTDOWN) {
+		mtx_unlock_spin(&po->po_mtx);
+		return (NULL);
+	}
+
 	if (po->po_curbuf == NULL)
 		if (pmclog_get_buffer(po) != 0) {
 			mtx_unlock_spin(&po->po_mtx);
@@ -686,7 +695,7 @@ pmclog_deconfigure_log(struct pmc_owner 
 int
 pmclog_flush(struct pmc_owner *po)
 {
-	int error, has_pending_buffers;
+	int error;
 
 	PMCDBG(LOG,FLS,1, "po=%p", po);
 
@@ -714,16 +723,13 @@ pmclog_flush(struct pmc_owner *po)
 	mtx_lock_spin(&po->po_mtx);
 	if (po->po_curbuf)
 		pmclog_schedule_io(po);
-	has_pending_buffers = !TAILQ_EMPTY(&po->po_logbuffers);
 	mtx_unlock_spin(&po->po_mtx);
 
-	if (has_pending_buffers) {
-		po->po_flags |= PMC_PO_IN_FLUSH; /* ask for a wakeup */
-		error = msleep(po->po_kthread, &pmc_kthread_mtx, PWAIT,
-		    "pmcflush", 0);
-		if (error == 0)
-			error = po->po_error;
-	}
+	/*
+	 * Initiate shutdown: no new data queued,
+	 * thread will close file on last block.
+	 */
+	po->po_flags |= PMC_PO_SHUTDOWN;
 
  error:
 	mtx_unlock(&pmc_kthread_mtx);

Modified: head/sys/sys/pmc.h
==============================================================================
--- head/sys/sys/pmc.h	Mon Mar  8 19:40:31 2010	(r204877)
+++ head/sys/sys/pmc.h	Mon Mar  8 19:58:00 2010	(r204878)
@@ -759,7 +759,7 @@ struct pmc_owner  {
 };
 
 #define	PMC_PO_OWNS_LOGFILE		0x00000001 /* has a log file */
-#define	PMC_PO_IN_FLUSH			0x00000010 /* in the middle of a flush */
+#define	PMC_PO_SHUTDOWN			0x00000010 /* in the process of shutdown */
 #define	PMC_PO_INITIAL_MAPPINGS_DONE	0x00000020
 
 /*

Modified: head/usr.sbin/pmcstat/pmcstat_log.c
==============================================================================
--- head/usr.sbin/pmcstat/pmcstat_log.c	Mon Mar  8 19:40:31 2010	(r204877)
+++ head/usr.sbin/pmcstat/pmcstat_log.c	Mon Mar  8 19:58:00 2010	(r204878)
@@ -1670,10 +1670,8 @@ pmcstat_print_log(void)
 int
 pmcstat_close_log(void)
 {
-	if (pmc_flush_logfile() < 0 ||
-	    pmc_configure_logfile(-1) < 0)
+	if (pmc_flush_logfile() < 0)
 		err(EX_OSERR, "ERROR: logging failed");
-	args.pa_flags &= ~(FLAG_HAS_OUTPUT_LOGFILE | FLAG_HAS_PIPE);
 	return (args.pa_flags & FLAG_HAS_PIPE ? PMCSTAT_EXITING :
 	    PMCSTAT_FINISHED);
 }