On Thu, 27 Oct 2022 13:15:23 -0700 Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > On Thu, Oct 27, 2022 at 12:55 PM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > > I think we need to update this code to squeeze in a del_timer_shutdown() to > > make sure that the timers are never restarted. > > So the reason the networking code does this is that it can't just do > the old 'sync()' thing, the timers are deleted in contexts where that > isn't valid. > > Which is also afaik why the networking code does that whole "timer > implies a refcount to the socket" and then does the > > if (del_timer(timer)) > sock_put() > > thing (ie if the del_timer failed - possibly because it was already > running - you leave the refcount alone). OK, so the above is assuming that the timer is always active, and del_timer() returns if it successfully removed it (where it can call sock_put()), but if del_timer() returns 0, that means the timer is currently running (or about to be), so it doesn't call sock_put(). > > So the networking code cannot do the del_timer_shutdown() for the same > reason it cannot do the del_timer_sync(): it can't afford to wait for > the timer to stop running. > > I suspect it needs something like a new "del_timer_shutdown_async()" > that isn't synchronous, but does that > > - acts as del_timer in that it doesn't wait, and returns a success if > it could just remove the pending case > > - does that "mark timer for shutdown" in that success case > > or something similar. > What about del_timer_try_shutdown(), that if it removes the timer, it sets the function to NULL (making it equivalent to a successful shutdown), otherwise it does nothing. Allowing the the timer to be rearmed. I think this would work in this case. -- Steve
