From 1f49a2c2aeb22d5abc6d4ea574ff63d37ca55fbe Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Date: Fri, 15 Aug 2008 12:45:09 -0400 Subject: x86: revert replace LOCK_PREFIX in futex.h Since we now use DS prefixes instead of NOP to remove LOCK prefixes, there are no longer any issues with instruction boundaries moving around. Depends on : x86 alternatives : fix LOCK_PREFIX race with preemptible kernel and CPU hotplug On Thu, 14 Aug 2008, Mathieu Desnoyers wrote: > > Changing the 0x90 (single-byte nop) currently used into a 0x3E DS segment > override prefix should fix this issue. Since the default of the atomic > instructions is to use the DS segment anyway, it should not affect the > behavior. Ok, so I think this is an _excellent_ patch, but I'd like to also then use LOCK_PREFIX in include/asm-x86/futex.h. See commit 9d55b9923a1b7ea8193b8875c57ec940dc2ff027. Linus Applies to 2.6.27-rc2 (and -rc3 unless hell broke loose in futex.h between rc2 and rc3). Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> CC: Linus Torvalds <torvalds@linux-foundation.org> CC: H. Peter Anvin <hpa@zytor.com> CC: Jeremy Fitzhardinge <jeremy@goop.org> CC: Roland McGrath <roland@redhat.com> CC: Ingo Molnar <mingo@elte.hu> Cc: Steven Rostedt <rostedt@goodmis.org> CC: Steven Rostedt <srostedt@redhat.com> CC: Thomas Gleixner <tglx@linutronix.de> CC: Peter Zijlstra <peterz@infradead.org> CC: Andrew Morton <akpm@linux-foundation.org> CC: David Miller <davem@davemloft.net> CC: Ulrich Drepper <drepper@redhat.com> CC: Rusty Russell <rusty@rustcorp.com.au> CC: Gregory Haskins <ghaskins@novell.com> CC: Arnaldo Carvalho de Melo <acme@redhat.com> CC: "Luis Claudio R. Goncalves" <lclaudio@uudg.org> CC: Clark Williams <williams@redhat.com> CC: Christoph Lameter <cl@linux-foundation.org> CC: Andi Kleen <andi@firstfloor.org> CC: Harvey Harrison <harvey.harrison@gmail.com> Signed-off-by: H. Peter Anvin <hpa@zytor.com> --- include/asm-x86/futex.h | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/include/asm-x86/futex.h b/include/asm-x86/futex.h index e7a76b37b333..d1b988ce080a 100644 --- a/include/asm-x86/futex.h +++ b/include/asm-x86/futex.h @@ -25,7 +25,7 @@ asm volatile("1:\tmovl %2, %0\n" \ "\tmovl\t%0, %3\n" \ "\t" insn "\n" \ - "2:\tlock; cmpxchgl %3, %2\n" \ + "2:\t" LOCK_PREFIX "cmpxchgl %3, %2\n" \ "\tjnz\t1b\n" \ "3:\t.section .fixup,\"ax\"\n" \ "4:\tmov\t%5, %1\n" \ @@ -64,7 +64,7 @@ static inline int futex_atomic_op_inuser(int encoded_op, int __user *uaddr) __futex_atomic_op1("xchgl %0, %2", ret, oldval, uaddr, oparg); break; case FUTEX_OP_ADD: - __futex_atomic_op1("lock; xaddl %0, %2", ret, oldval, + __futex_atomic_op1(LOCK_PREFIX "xaddl %0, %2", ret, oldval, uaddr, oparg); break; case FUTEX_OP_OR: @@ -122,7 +122,7 @@ static inline int futex_atomic_cmpxchg_inatomic(int __user *uaddr, int oldval, if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) return -EFAULT; - asm volatile("1:\tlock; cmpxchgl %3, %1\n" + asm volatile("1:\t" LOCK_PREFIX "cmpxchgl %3, %1\n" "2:\t.section .fixup, \"ax\"\n" "3:\tmov %2, %0\n" "\tjmp 2b\n" -- cgit v1.2.3