On 30.07.21 22:49, Guenter Roeck wrote: > 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. Jan -- Siemens AG, T RDA IOT Corporate Competence Center Embedded Linux
