Zoltan Menyhart wrote:
Christoph Lameter wrote:
[...]
void fastcall unlock_buffer(struct buffer_head *bh)
{
+ smp_mb__before_clear_bit();
clear_buffer_locked(bh);
- smp_mb__after_clear_bit();
wake_up_bit(&bh->b_state, BH_Lock);
}
The sequence:
smp_mb__before_clear_bit();
clear_buffer_locked(bh);
is correct (yet not efficient for all architectures).
Yes, this is explicitly documented in the wake_up_bit interface. I
don't really think it needs to be changed, does it? Bill did most
of this work I think, so I've cc'ed him.
We have got here two unrelated operations: ending a critical section
and waking up the eventual waiters. What we need is a barrier between
these two unrelated operations.
It is not "smp_mb__after_clear_bit()" but a simple "smp_mb()".
The correct code is:
void fastcall unlock_buffer(struct buffer_head *bh)
{
smp_mb__before_clear_bit();
clear_buffer_locked(bh);
smp_mb();
wake_up_bit(&bh->b_state, BH_Lock);
}
If you were going to do that, I'd prefer my suggestion.
clear_buffer_locked(); /* clear_bit_unlock */
smp_mb__after_clear_bit_unlock();
wake_up_bit()
Nick
--
Send instant messages to your online friends http://au.messenger.yahoo.com
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
