From 2f74759056797054122cdc70844137f70bb3f626 Mon Sep 17 00:00:00 2001 From: OGAWA Hirofumi Date: Thu, 7 Jun 2012 22:20:18 +0900 Subject: [PATCH] x86/alternatives: Use atomic_xchg() instead atomic_dec_and_test() for stop_machine_text_poke() stop_machine_text_poke() uses atomic_dec_and_test() to select one of the CPUs executing that function to actually modify the code. Since the variable is initialized to 1, subsequent CPUs will make the variable go negative. Since going negative is uncommon/unexpected in typical dec_and_test usage change this user to atomic_xchg(). This was found using a patch that warns on dec_and_test going negative. Signed-off-by: OGAWA Hirofumi Acked-by: Steven Rostedt [ Rewrote changelog ] Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/87zk8fgsx9.fsf@devron.myhome.or.jp Signed-off-by: Ingo Molnar --- arch/x86/kernel/alternative.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index 1f84794f0759..53231a045d3d 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -664,7 +664,7 @@ static int __kprobes stop_machine_text_poke(void *data) struct text_poke_param *p; int i; - if (atomic_dec_and_test(&stop_machine_first)) { + if (atomic_xchg(&stop_machine_first, 0)) { for (i = 0; i < tpp->nparams; i++) { p = &tpp->params[i]; text_poke(p->addr, p->opcode, p->len); -- 2.45.2