I wonder if "unlock_buffer()" works correctly on ia64...
As far As I can see, nothing makes it sure that data modifications
issued inside the critical section be globally visible before the
"BH_Lock" bit gets cleared.
- Either an "smp_mb__before_clear_bit()" is lacking
(if we want to keep the existing definition of "clear_bit()"
with its "acq" semantics)
- or "clear_bit()" should use the "rel" semantics
(since we are actually _releasing_ a lock)
Thanks,
Zoltan Menyhart
buffer.c:
void fastcall unlock_buffer(struct buffer_head *bh)
{
clear_buffer_locked(bh);
smp_mb__after_clear_bit();
wake_up_bit(&bh->b_state, BH_Lock);
}
asm-ia64/bitops.h:
/*
* clear_bit() has "acquire" semantics.
*/
#define smp_mb__before_clear_bit() smp_mb()
#define smp_mb__after_clear_bit() do { /* skip */; } while (0)
/**
* clear_bit - Clears a bit in memory
* @nr: Bit to clear
* @addr: Address to start counting from
*
* clear_bit() is atomic and may not be reordered. However, it does
* not contain a memory barrier, so if it is used for locking purposes,
* you should call smp_mb__before_clear_bit() and/or smp_mb__after_clear_bit()
* in order to ensure changes are visible on other processors.
*/
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