[Ocfs2-tools-devel] [PATCH 2/2] o2hbmonitor: add semaphore

[Srinivas Eeda]

add semaphore to limit to one o2hbmonitor per node

Signed-off-by: Srinivas Eeda <srinivas.eeda at oracle.com>
---
 o2monitor/o2hbmonitor.c |   39 +++++++++++++++++++++++++++++++++++++++
 1 files changed, 39 insertions(+), 0 deletions(-)

diff --git a/o2monitor/o2hbmonitor.c b/o2monitor/o2hbmonitor.c
index f01da76..d7cc92c 100644
--- a/o2monitor/o2hbmonitor.c
+++ b/o2monitor/o2hbmonitor.c
@@ -43,6 +43,8 @@
 #include <libgen.h>
 #include <syslog.h>
 #include <errno.h>
+#include <sys/ipc.h>
+#include <sys/sem.h>
 
 #define SYS_CONFIG_DIR			"/sys/kernel/config"
 #define O2HB_CLUSTER_DIR		SYS_CONFIG_DIR"/cluster"
@@ -61,6 +63,8 @@
 #define SLOW_POLL_IN_SECS		10
 #define FAST_POLL_IN_SECS		2
 
+#define O2HB_SEM_MAGIC_KEY		0x4A32594B
+
 char *progname;
 int interactive;
 int warn_threshold_percent;
@@ -300,6 +304,32 @@ static void monitor(void)
 	}
 }
 
+static int getlock(void)
+{
+	int semid, vals[]={0};
+	struct sembuf trylock[] = {{0, 0, SEM_UNDO|IPC_NOWAIT},
+				   {0, 1, SEM_UNDO|IPC_NOWAIT}};
+
+	semid = semget(O2HB_SEM_MAGIC_KEY, 1, 0);
+	if (semid < 0) {
+		printf("creating sem\n");
+		semid = semget(O2HB_SEM_MAGIC_KEY, 1,
+			       IPC_CREAT|IPC_EXCL|S_IRUSR);
+		if (semid < 0)
+			goto out;
+		semctl(semid, 0, SETALL, vals);
+		if (semop(semid, trylock, 2) < 0)
+			goto out;
+		else
+			return 0;
+	}
+	if (semop(semid, trylock, 2) < 0)
+		goto out;
+	return 0;
+out:
+	return errno;
+}
+
 static void usage(void)
 {
 	fprintf(stderr, "usage: %s [-w percent] -[ivV]\n", progname);
@@ -360,6 +390,15 @@ int main(int argc, char **argv)
 	}
 
 	openlog(progname, LOG_CONS|LOG_NDELAY, LOG_DAEMON);
+	if ((ret = getlock())) {
+	       if (ret == EAGAIN)
+		       syslog(LOG_WARNING, "o2hbmonitor already running\n");
+	       else
+		       syslog(LOG_WARNING, "o2hbmonitor failed to start\n");
+	       closelog();
+	       return ret;
+	}
+		
 	monitor();
 	closelog();
 
-- 
1.5.6.5