Commit a2a64769 authored Jun 09, 2005 by Christoph Lameter Committed by Tony Luck Jun 09, 2005

[IA64] Fix race condition in the rt_sigprocmask fastcall

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>

parent 1834cd9f

arch/ia64/kernel/fsys.S

+2 −2

Original line number	Diff line number	Diff line
		@@ -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