Sourabh Jain <[email protected]> writes: >> Looking at the code, we already have a mechanism to register a crash >> shutdown handler which anyways is getting called from >> default_machine_crash_shutdown(). So, I think we could use this generic >> crash handler register mechanism and keep the wdt specific calls within >> pseries/setup.c file... > > That's a good idea. I wasn't aware of this crash handler. > > The main reason I wanted to stop the watchdog as soon as the kernel > enters the architecture-specific crash code is that, on PowerPC, the > crash path sends IPIs to all other CPUs and waits for their response > before continuing. Because of this, I thought it would be better to > stop the watchdog as early as possible. > > I knew there was an IPI timeout, but I just checked and it's set to > 10 seconds. See crash_kexec_prepare_cpus() in crash.c. >
That's just the max worst case timeout value, which is unlikely to be hit. FWIW, the watchdog timeout value in the example usage for sbd.8.pod.in file seems to be 15sec. > The crash handler is called after the IPI wait. So, in theory, the watchdog > timeout could occur before the IPI timeout. But I think that's a very > unlikely > scenario, though. I agree. > So I think disabling the watchdog from the crash handler > is a reasonable approach. > > Please share your thoughts. > yup! I agree, the crash handler looks to be a much better approach since it avoids, hcall definitions scattered in common powerpc/kexec/crash.c file. This also provides setjmp/longjmp for recovering from any bogus exceptions during crash handling. But we will know more when you will give it a try! -ritesh
