Zbigniew Jędrzejewski-Szmek
ab596e4cde
Closes https://github.com/systemd/systemd/issues/35405. Apparently some watchdog devices can be opened, but then the pings start failing after some time. Since the timestamp of the last successful ping is not updated, we try to ping again immediately, causing a busy loop and excessive logging. After trying a few different approaches to fit this into the existing framework without changing the logic too much, I settled on an approach with a second timestamp. In particular, the timestamp of the last successful ping is public, exposed as WatchdogLastPingTimestamp over dbus. It'd be wrong to redefine this to mean the last ping *attempt*. So we need a second timestamp in some form. Also, if we give up on pinging, we probably should attempt to disarm the watchdog. It's possible that the pinging fails, but the watchdog would still fire. I don't think we want that, since it seems that our internal loop is working, it's just the watchdog that is broken. Structured message with SD_MESSAGE_WATCHDOG_PING_FAILED is logged if we fail to ping. I tested this by attaching gdb to pid 1 and calling close(watchdog_fd). We get a bunch of warning messages and then an attempt to close the watchdog: Mar 21 15:46:17 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:20 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:23 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:26 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:29 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:32 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:35 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:37 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:40 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:43 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:46 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:49 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:52 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:55 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0: Bad file descriptor Mar 21 15:46:58 fedora systemd[1]: Failed to ping hardware watchdog /dev/watchdog0, closing watchdog after 15 attempts: Bad file descriptor Mar 21 15:46:58 fedora systemd[1]: Failed to disable hardware watchdog, ignoring: Bad file descriptor Mar 21 15:46:58 fedora systemd[1]: Failed to disarm watchdog timer, ignoring: Bad file descriptor
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