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[ARM] 3310/1: add a comment about the possible __kuser_cmpxchg transient false

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Patch from Nicolas Pitre

The pre ARMv5 implementation can be aborted if an exception occurs in
the middle of it.  Because of that, the ARMv6 implementation doesn't
re-attempt the operation on a failed strex either.  Let's make this
transient nature of such a false positive more explicit in the
definition.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Nicolas Pitre 2006-02-08 21:19:37 +00:00 committed by Russell King
parent 49bca4c281
commit 5964eae835
1 changed files with 6 additions and 1 deletions
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arch/arm/kernel/entry-armv.S
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@ -709,7 +709,12 @@ __kuser_memory_barrier: @ 0xffff0fa0
* The C flag is also set if *ptr was changed to allow for assembly
* optimization in the calling code.
*
* Note: this routine already includes memory barriers as needed.
* Notes:
*
* - This routine already includes memory barriers as needed.
*
* - A failure might be transient, i.e. it is possible, although unlikely,
* that "failure" be returned even if *ptr == oldval.
*
* For example, a user space atomic_add implementation could look like this:
*