On 07/25/2014 12:10 PM, Peter Zijlstra wrote:
On Thu, Jul 24, 2014 at 04:38:28PM -0400, Waiman Long wrote:Yes, I think I may have a solution for that. Borislav, can you apply the following patch on top of the lockdep patch to see if it can fix the problem? diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index d24e433..507a8ce 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -3595,6 +3595,12 @@ void lock_acquire(struct lockdep_map *lock, unsigned int raw_local_irq_save(flags); check_flags(flags); + /* + * An interrupt recursive read in interrupt context can be considered + * to be the same as a recursive read from checking perspective. + */ + if ((read == 3)&& in_interrupt()) + read = 2; current->lockdep_recursion = 1; trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip); __lock_acquire(lock, subclass, trylock, read, check,Just had another look at the initial patch and it cannot be right, even with the above. The problem is you cannot use in_interrupt() in check_deadlock(). Check_deadlock() must be context invariant, it should only test the chain state and not rely on where or when its called.
I am planning to take out the check in check_deadlock and only have the test in lock_acquire which change a 3 to 2 when in interrupt context. Now my question is whether to do it as a new patch on top of the existing one in tip or a total replacement. I also intend to use symbolic names for the read states for better readability as suggested by John.
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