From: Peter Zijlstra Date: Mon, 26 Mar 2012 11:16:15 +0000 (+0200) Subject: sched/x86/smp: Do not enable IRQs over calibrate_delay() X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=bc758133ed73d4b06952bec21da23e28e62bf3ba;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git sched/x86/smp: Do not enable IRQs over calibrate_delay() We should not ever enable IRQs until we're fully set up. This opens up a window where interrupts can hit the cpu and interrupts can do wakeups, wakeups need state that isn't set-up yet, in particular this cpu isn't elegible to run tasks, so if any cpu-affine task that got created in CPU_UP_PREPARE manages to get a wakeup, its affinity mask will get broken and we'll run into lots of 'interesting' problems. Signed-off-by: Peter Zijlstra Cc: Linus Torvalds Link: http://lkml.kernel.org/n/tip-yaezmlbriluh166tfkgni22m@git.kernel.org Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 58f78165d308..89571a0c4a49 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -219,14 +219,9 @@ static void __cpuinit smp_callin(void) * Update loops_per_jiffy in cpu_data. Previous call to * smp_store_cpu_info() stored a value that is close but not as * accurate as the value just calculated. - * - * Need to enable IRQs because it can take longer and then - * the NMI watchdog might kill us. */ - local_irq_enable(); calibrate_delay(); cpu_data(cpuid).loops_per_jiffy = loops_per_jiffy; - local_irq_disable(); pr_debug("Stack at about %p\n", &cpuid); /*