On Fri 2017-06-23 21:16:37, Luis R. Rodriguez wrote: > On Fri, Jun 23, 2017 at 07:56:11PM +0200, Luis R. Rodriguez wrote: > > On Fri, Jun 23, 2017 at 06:16:19PM +0200, Luis R. Rodriguez wrote: > > > On Thu, Jun 22, 2017 at 05:19:36PM +0200, Petr Mladek wrote: > > > > On Fri 2017-05-26 14:12:28, Luis R. Rodriguez wrote: > > > > > --- a/kernel/kmod.c > > > > > +++ b/kernel/kmod.c > > > > > @@ -178,6 +175,7 @@ int __request_module(bool wait, const char *fmt, ...) > > > > > ret = call_modprobe(module_name, wait ? UMH_WAIT_PROC : UMH_WAIT_EXEC); > > > > > > > > > > atomic_inc(&kmod_concurrent_max); > > > > > + wake_up_all(&kmod_wq); > > > > > > > > Does it make sense to wake up all waiters when we released the resource > > > > only for one? IMHO, a simple wake_up() should be here. > > > > > > Then we should wake_up() also on failure, otherwise we have the potential > > > to not wake some in a proper time. > > > > I checked and it turns out we have no error paths after we consume a kmod > > ticket, if you will. Once we bump with atomic_dec_if_positive() we assume > > we're moving forward with an attempt, and the only failure path is already > > bundled with a wake at the end of the __request_module() call. > > > > Then the next question would be *who* exactly gets woken up next if we just > > use wake_up() ? The common core wake up code varies depending on use and > > all this reminded me of the complexity we just don't need, so I have now > > converted to use swait. swait uses list_add() if empty and then iterates > > with list_first_entry() on wakeup, so that should get the first item added > > to the wait list. > > > > Works with me. Will run a test a before v4 is sent, but since only 2 patches > > are modified will only send a respective update for these 2 patches. > > Alright, this worked out well! Its just a tiny bit slower on test cases 0008 > and 0009 (few seconds) but that's fine, its natural due to the lack of the > swake_up_all(). This is interesting. I guess that it was faster with swake_up_all() because it worked as a speculative pre-wake. I mean that it takes some time between adding a process into run-queue and really running it. IMHO, swake_up_all() caused that __request_module() callers were more often really running and trying to pass that atomic_dec_if_positive(&kmod_concurrent_max) >= 0). Best Regards, Petr -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
