wdmd/main.c

[David Teigland]

wdmd/main.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

New commits:
commit 7e43623a8ccf59411e4a43d5aff48d9326fbed26
Author: David Teigland 
Date:   Wed Nov 18 13:50:21 2015 -0600

wdmd: prevent probe while watchdog is used

If the wdmd daemon is killed uncleanly, /dev/watchdog
    is closed uncleanly and the watchdog should fire to
    reset the machine.

If 'wdmd -p' is run to probe available watchdog devices
    after wdmd is killed and before the machine is reset,
    it will unintentionally interfere with the expiring
    watchdog by doing open/magic-close on each device.
    This silently prevents the watchdog from firing when
    it should.

The probe function can check for the shm flag before
    touching any watchdog devices, just like another wdmd
    daemon process does, to avoid interfering with the
    watchdog state of a previous wdmd daemon that was
    terminated uncleanly.

diff --git a/wdmd/main.c b/wdmd/main.c
index c29667f..911d833 100644
--- a/wdmd/main.c
+++ b/wdmd/main.c
@@ -1604,7 +1604,18 @@ int main(int argc, char *argv[])
    }

if (do_probe) {
+		rv = setup_shm();
+		if (rv < 0) {
+			fprintf(stderr, "cannot probe watchdog devices while wdmd is in use.\n");
+			openlog("wdmd-probe", LOG_CONS | LOG_PID, LOG_DAEMON);
+			syslog(LOG_ERR, "cannot probe watchdog devices while wdmd is in use.\n");
+			exit(EXIT_FAILURE);
+		}
+
    	rv = probe_watchdog();
+
+		close_shm();
+
    	if (rv < 0)
    		exit(EXIT_FAILURE);
    	else