>>>>> "Waiman" == Waiman Long <waiman.long@xxxxxx> writes: Waiman> On 07/24/2014 02:36 PM, Peter Zijlstra wrote: >> On Thu, Jul 24, 2014 at 11:18:16AM -0700, Linus Torvalds wrote: >>> On Thu, Jul 24, 2014 at 5:58 AM, Peter Zijlstra<peterz@xxxxxxxxxxxxx> wrote: >>>> So going by the nifty picture rostedt made: >>>> >>>> [ 61.454336] CPU0 CPU1 >>>> [ 61.454336] ---- ---- >>>> [ 61.454336] lock(&(&p->alloc_lock)->rlock); >>>> [ 61.454336] local_irq_disable(); >>>> [ 61.454336] lock(tasklist_lock); >>>> [ 61.454336] lock(&(&p->alloc_lock)->rlock); >>>> [ 61.454336]<Interrupt> >>>> [ 61.454336] lock(tasklist_lock); >>> So this *should* be fine. It always has been in the past, and it was >>> certainly the *intention* that it should continue to work with >>> qrwlock, even in the presense of pending writers on other cpu's. >>> >>> The qrwlock rules are that a read-lock in an interrupt is still going >>> to be unfair and succeed if there are other readers. >> Ah, indeed. Should have checked :/ >> >>> So it sounds to me like the new lockdep rules in tip/master are too >>> strict and are throwing a false positive. >> Right. Waiman can you have a look? Waiman> Yes, I think I may have a solution for that. Waiman> Borislav, can you apply the following patch on top of the lockdep patch Waiman> to see if it can fix the problem? Waiman> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c Waiman> index d24e433..507a8ce 100644 Waiman> --- a/kernel/locking/lockdep.c Waiman> +++ b/kernel/locking/lockdep.c Waiman> @@ -3595,6 +3595,12 @@ void lock_acquire(struct lockdep_map *lock, Waiman> unsigned int Waiman> raw_local_irq_save(flags); Waiman> check_flags(flags); Waiman> + /* Waiman> + * An interrupt recursive read in interrupt context can be Waiman> considered Waiman> + * to be the same as a recursive read from checking perspective. Waiman> + */ Waiman> + if ((read == 3) && in_interrupt()) Waiman> + read = 2; current-> lockdep_recursion = 1; Waiman> trace_lock_acquire(lock, subclass, trylock, read, check, Waiman> nest_lock, ip); Waiman> __lock_acquire(lock, subclass, trylock, read, check, Instead of the magic numbers 1,2,3, could you use some nicely named constants here instead? John -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
