From: Pierre-Marc Fournier <pierre-marc.fournier@polymtl.ca>
Date: Sat, 27 Feb 2010 17:06:04 +0000 (-0500)
Subject: improve keepalive by changing the location of the unconnected buffers counter
X-Git-Tag: v0.3~14
X-Git-Url: https://git.lttng.org/?p=ust.git;a=commitdiff_plain;h=d5adede06d9dc0c4675c4c4052eb98f74973f4a5

improve keepalive by changing the location of the unconnected buffers counter

to a location that guarantees the buffer has been mapped by the daemon
Fixes a race.
---

diff --git a/libust/tracectl.c b/libust/tracectl.c
index c34a3ce..916b354 100644
--- a/libust/tracectl.c
+++ b/libust/tracectl.c
@@ -357,10 +357,7 @@ static int do_cmd_get_shmid(const char *recvbuf, struct ustcomm_source *src)
 		}
 	}
 
-	if(found) {
-		buffers_to_export--;
-	}
-	else {
+	if(!found) {
 		ERR("channel not found (%s)", channel_and_cpu);
 	}
 
@@ -695,6 +692,14 @@ static int do_cmd_get_subbuffer(const char *recvbuf, struct ustcomm_source *src)
 
 			list_add(&bc->list, &blocked_consumers);
 
+			/* Being here is the proof the daemon has mapped the buffer in its
+			 * memory. We may now decrement buffers_to_export.
+			 */
+			if(atomic_long_read(&buf->consumed) == 0) {
+				DBG("decrementing buffers_to_export");
+				buffers_to_export--;
+			}
+
 			break;
 		}
 	}