Messages in this thread | | | Subject | Incorrect atomic usage in cx88-alsa driver | From | Benjamin Herrenschmidt <> | Date | Tue, 08 May 2007 13:25:06 +1000 |
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Hi !
So I see this construct:
if (test_and_set_bit(0, &chip->opened)) return -EBUSY;
.../...
return 0; _error: dprintk(1,"Error opening PCM!\n"); clear_bit(0, &chip->opened); smp_mb__after_clear_bit(); return err;
So that's basically an attempt at doing a spinlock. The problem is your barrier is wrong at the end. Better would be:
done: smp_mb__before_clear_bit(); clear_bit(0, &chip->opened);
Though it's still less optimal that doing:
if (!spin_trylock(...)) goto bail;
.../...
done: spin_unlock(...)
If you really want to stick to bitops, then you may want to look at Nick's upcoming patches adding some bitops with appropriate lock semantics.
Cheers, Ben.
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