On 30.07.21 22:49, Guenter Roeck wrote:Good point. You are correct.
On 7/30/21 12:39 PM, Jan Kiszka wrote:
From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
We must not pet a running watchdog when handle_boot_enabled is off
because this requests to only start doing that via userspace, not during
probing.
The scope of the changed function is quite limited. See the
definition of watchdog_set_last_hw_keepalive(). On top of that,
__watchdog_ping() does a bit more than just ping the watchdog,
and it only pings the watchdog in limited circumstances. On top of that,
the scope of handle_boot_enabled is different: If enabled, it tells
the watchdog core to keep pinging a watchdog until userspace opens
the device. This is about continuous pings, not about an initial one.
Given that, I'd rather have the watchdog subsystem issue an additional
ping than risking a regression.
The only driver calling watchdog_set_last_hw_keepalive() is rti_wdt.c.
Does this patch solve a specific problem observed with that watchdog ?
Yes, it unbreaks support for handle_boot_enabled=no by not starting the
automatic pinging of the kernel until userspace opens the device.
Without this fix, the core will prematurely start kernel-side pinging,
and hanging userspace will never be detected.