Nick Piggin wrote on Thursday, March 30, 2006 11:35 PM
> > >The memory ordering that above combination should produce is a
> > >Linux style smp_mb before the clear_bit. Not a release.
> >
> > Whoever designed the smp_mb_before/after_* clearly understand the
> > difference between a bidirectional smp_mb() and a one-way memory
> > ordering. If smp_mb_before/after are equivalent to smp_mb, what's
> > the point of introducing another interface?
> >
> They are not. They provide equivalent barrier when performed
> before/after a clear_bit, there is a big difference.
The usage so far that I can see for
smp_mb__before_clear_bit()
clear_bit
is to close a critical section with clear_bit. I will be hard impressed
to see a usage that allows stuff follows clear_bit to pass clear_bit, but
not to pass the smp_mb_before_xxx.
<end of critical section>
smp_mb_before_clear_bit
clear_bit
<begin other code>
But if you stand on the ground of smp_mb_before_xxx protects clear_bit
from occurring before the "end of critical section", then smp_mb_before
is such a brain dead interface and it is another good reason for having
an explicit ordering mode built into the clear_bit.
-
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]
