From: Kirill Korotaev Date: Mon, 14 Nov 2005 00:07:30 +0000 (-0800) Subject: [PATCH] stop_machine() vs. synchronous IPI send deadlock X-Git-Tag: v2.6.15-rc2~156 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4557398f8cbaf9f254cff747534b4724c7f75c4f;p=linux-2.6 [PATCH] stop_machine() vs. synchronous IPI send deadlock This fixes deadlock of stop_machine() vs. synchronous IPI send. The problem is that stop_machine() disables interrupts before disabling preemption on other CPUs. So if another CPU is preempted and then calls something like flush_tlb_all() it will deadlock with CPU doing stop_machine() and which can't process IPI due to disabled IRQs. I changed stop_machine() to do the same things exactly as it does on other CPUs, i.e. it should disable preemption first on _all_ CPUs including itself and only after that disable IRQs. Signed-off-by: Kirill Korotaev Cc: Rusty Russell Cc: "Andrey Savochkin" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index 84a9d18aa8..b3d4dc858e 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -119,13 +119,12 @@ static int stop_machine(void) return ret; } - /* Don't schedule us away at this point, please. */ - local_irq_disable(); - /* Now they are all started, make them hold the CPUs, ready. */ + preempt_disable(); stopmachine_set_state(STOPMACHINE_PREPARE); /* Make them disable irqs. */ + local_irq_disable(); stopmachine_set_state(STOPMACHINE_DISABLE_IRQ); return 0; @@ -135,6 +134,7 @@ static void restart_machine(void) { stopmachine_set_state(STOPMACHINE_EXIT); local_irq_enable(); + preempt_enable_no_resched(); } struct stop_machine_data