Messages in this thread | | | Date | Wed, 23 Apr 2014 10:10:01 +0200 | From | Sebastian Andrzej Siewior <> | Subject | Re: BUG: spinlock trylock failure on UP, i.MX28 3.12.15-rt25 |
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On 04/22/2014 04:09 PM, Peter Zijlstra wrote: > On Tue, Apr 22, 2014 at 09:46:57AM -0400, Steven Rostedt wrote: >>> According to lockdep a trylock should not fail on UP. > > Oh!? Where does it say that? A trylock can fail at all times.
kernel/locking/spinlock_debug.c:
int do_raw_spin_trylock(raw_spinlock_t *lock) { int ret = arch_spin_trylock(&lock->raw_lock);
if (ret) debug_spin_lock_after(lock); #ifndef CONFIG_SMP /* * Must not happen on UP: */ SPIN_BUG_ON(!ret, lock, "trylock failure on UP"); #endif return ret; }
How can a trylock (spinlock, not mutex) fail on UP? That would mean the lock is not interrupt safe. Unless, you attempt to take the lock from interrupt context via trylock while in general you take the spinlock in process context with interrupts enabled.
Sebastian
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