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Commit 0aa002fe authored by Tejun Heo's avatar Tejun Heo Committed by Thomas Gleixner
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarCyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: default avatarPekka Enberg <penberg@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: brgerst@gmail.com
LKML-Reference: <4D00B3B9.7060702@kernel.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 0e3fa13f

arch/x86/kernel/apic/apic.c

+9 −12
Original line number Diff line number Diff line
@@ -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

}