lkml.org 
[lkml]   [2006]   [Dec]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 3/3] WorkStruct: Use direct assignment rather than cmpxchg()
Date
Andrew Morton <akpm@osdl.org> wrote:

> and we can assume (and ensure) that a failing test_and_set_bit() will not
> write to the affected word at all.

You may not assume that; and indeed that is not so in the generic
spinlock-based bitops or ARM pre-v6 or PA-RISC or sparc32 or ...

Remember: if you have to put a conditional jump in there, it's going to fail
one way or the other a certain percentage of the time, and that's going to
cause a pipeline stall, and these ops are used quite a lot.

OTOH, I don't know that the stall would be that bad since the spin_lock and
spin_unlock may cause a stall anyway.

David
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-12-07 21:09    [W:0.294 / U:0.208 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site