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Subject[tip:x86/apic-cleanups] x86: apic: Cleanup and simplify setup_local_APIC()
Commit-ID:  0aa002fe602939370e9476e5ec32b562000a0425
Gitweb: http://git.kernel.org/tip/0aa002fe602939370e9476e5ec32b562000a0425
Author: Tejun Heo <tj@kernel.org>
AuthorDate: Thu, 9 Dec 2010 11:47:21 +0100
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 10 Dec 2010 13:46:26 +0100

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 <tj@kernel.org>
Acked-by: Cyrill Gorcunov <gorcunov@gmail.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: brgerst@gmail.com
LKML-Reference: <4D00B3B9.7060702@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/kernel/apic/apic.c | 21 +++++++++------------
1 files 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
}

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