lkml.org 
[lkml]   [2015]   [Feb]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH V3] x86 spinlock: Fix memory corruption on completing completions
On 02/12, Raghavendra K T wrote:
>
> @@ -191,8 +189,7 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
> * We need to check "unlocked" in a loop, tmp.head == head
> * can be false positive because of overflow.
> */
> - if (tmp.head == (tmp.tail & ~TICKET_SLOWPATH_FLAG) ||
> - tmp.head != head)
> + if (__tickets_equal(tmp.head, tmp.tail) || tmp.head != head)
> break;

Ah, it seems that "tmp.head != head" should be turned into
!__tickets_equal(), no?

Suppose that TICKET_SLOWPATH_FLAG is set after the first ACCESS_ONCE(head),
then tmp.head != head will be true before the first unlock we are waiting
for.

And perhaps you can turn these ACCESS_ONCE into READ_ONCE as well.

Oleg.



\
 
 \ /
  Last update: 2015-02-12 15:01    [W:0.051 / U:0.752 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site