On 01/09/2022 13:44, Greg KH wrote: > [...] >>> How are we supposed to know this here? >>> >> >> Reading the code? >> Or you mean, in the commit description this should be mentioned? > > Yes, and in the comment as this type of call is very rare and should > almost never be used. OK, I can add that, for sure. >> [...] >> I don't think it is so simple - we are in the panic path. > > Great, then the lock doesn't matter :) > >> So, imagine the lock was taken in CPU0, where GSMI is doing some >> operation. During that operation, CPU1 panics! >> >> When that happens, panic() executes in CPU1, disabling CPU0 through >> "strong" mechanisms (NMI). So, CPU0 had the lock, it is now off, and >> when CPU1 goes through the panic notifiers, it'll eventually wait >> forever for this lock in the GSMI handler, unless we have this patch >> that would prevent the handler to run in such case. >> Makes sense? > > I'm trying to say "if you are in panic, never grab the lock in the first > place". So change the place when you grab the lock, not here. > Evan, any comment here? I think the patch is still well suited for this case. Suggestions on how to improve it are welcome, of course. I honestly didn't understand exactly what you're suggesting Greg... Mind clarifying? Cheers, Guilherme
