From 0aa002fe602939370e9476e5ec32b562000a0425 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 9 Dec 2010 11:47:21 +0100 Subject: [PATCH] x86: apic: Cleanup and simplify setup_local_APIC() setup_local_APIC() is used to setup local APIC early during CPU initialization and already assumes that preemption is disabled on entry. However, The function unnecessarily disables and enables preemption and uses smp_processor_id() multiple times in and out of the nested preemption disabled section. This gives the wrong impression that the function might be able to handle being called with preemption enabled and/or migrated to another processor in the middle. Make it clear that the function is always called with preemption disabled, drop the confusing preemption disable block and call smp_processor_id() once at the beginning of the function. Signed-off-by: Tejun Heo Acked-by: Cyrill Gorcunov Reviewed-by: Pekka Enberg Cc: Yinghai Lu Cc: brgerst@gmail.com LKML-Reference: <4D00B3B9.7060702@kernel.org> Signed-off-by: Thomas Gleixner --- arch/x86/kernel/apic/apic.c | 21 +++++++++------------ 1 file changed, 9 insertions(+), 12 deletions(-) diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c index 8933936..c0f6426 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -1195,12 +1195,15 @@ static void __cpuinit lapic_setup_esr(void) oldvalue, value); } - /** * setup_local_APIC - setup the local APIC + * + * Used to setup local APIC while initializing BSP or bringin up APs. + * Always called with preemption disabled. */ void __cpuinit setup_local_APIC(void) { + int cpu = smp_processor_id(); unsigned int value, queued; int i, j, acked = 0; unsigned long long tsc = 0, ntsc; @@ -1225,8 +1228,6 @@ void __cpuinit setup_local_APIC(void) #endif perf_events_lapic_init(); - preempt_disable(); - /* * Double-check whether this APIC is really registered. * This is meaningless in clustered apic mode, so we skip it. @@ -1342,21 +1343,19 @@ void __cpuinit setup_local_APIC(void) * TODO: set up through-local-APIC from through-I/O-APIC? --macro */ value = apic_read(APIC_LVT0) & APIC_LVT_MASKED; - if (!smp_processor_id() && (pic_mode || !value)) { + if (!cpu && (pic_mode || !value)) { value = APIC_DM_EXTINT; - apic_printk(APIC_VERBOSE, "enabled ExtINT on CPU#%d\n", - smp_processor_id()); + apic_printk(APIC_VERBOSE, "enabled ExtINT on CPU#%d\n", cpu); } else { value = APIC_DM_EXTINT | APIC_LVT_MASKED; - apic_printk(APIC_VERBOSE, "masked ExtINT on CPU#%d\n", - smp_processor_id()); + apic_printk(APIC_VERBOSE, "masked ExtINT on CPU#%d\n", cpu); } apic_write(APIC_LVT0, value); /* * only the BP should see the LINT1 NMI signal, obviously. */ - if (!smp_processor_id()) + if (!cpu) value = APIC_DM_NMI; else value = APIC_DM_NMI | APIC_LVT_MASKED; @@ -1364,11 +1363,9 @@ void __cpuinit setup_local_APIC(void) value |= APIC_LVT_LEVEL_TRIGGER; apic_write(APIC_LVT1, value); - preempt_enable(); - #ifdef CONFIG_X86_MCE_INTEL /* Recheck CMCI information after local APIC is up on CPU #0 */ - if (smp_processor_id() == 0) + if (!cpu) cmci_recheck(); #endif } -- 2.7.4