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[IA64] Fix race condition in the rt_sigprocmask fastcall

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current->blocked will be set to the value of current->thread_info->flags if the
cmpxchg to update thread_info->flags fails. For performance reasons the store into
current->blocked was placed in the cmpxchg loop. However, the cmpxchg overwrites the
register holding the value to be stored. In the rare case of a retry the value of
thread_info->flags will be written into current->blocked.

The fix is to use another register so that the register containing the current->blocked
value is not overwritten.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This commit is contained in:
Christoph Lameter 2005-06-09 12:29:00 -07:00 committed by Tony Luck
parent 1834cd9fd2
commit a2a64769d0
1 changed files with 2 additions and 2 deletions
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4
arch/ia64/kernel/fsys.S
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@ -460,9 +460,9 @@ EX(.fail_efault, ld8 r14=[r33]) // r14 <- *set
;;
st8 [r2]=r14 // update current->blocked with new mask
cmpxchg4.acq r14=[r9],r18,ar.ccv // current->thread_info->flags <- r18
cmpxchg4.acq r8=[r9],r18,ar.ccv // current->thread_info->flags <- r18
;;
cmp.ne p6,p0=r17,r14 // update failed?
cmp.ne p6,p0=r17,r8 // update failed?
(p6) br.cond.spnt.few 1b // yes -> retry
#ifdef CONFIG_SMP