linux-kernel - Where system interrupts get disabled at LAPIC timer handler execution?

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Message-ID: <SNT111-DS20BA35E3097019A39A8694A7BC0@phx.gbl>
Date:	Fri, 16 Jul 2010 10:25:32 +0100
From:	"limp" <johnkyr83@...mail.com>
To:	<linux-kernel@...r.kernel.org>
Subject: Where system interrupts get disabled at LAPIC timer handler execution?

Dear all,

I am trying to demystify what happens when the kernel has configured to use
LAPIC timer as its timer and I've ran into some problems/questions.

AFAIK, when a LAPIC timer interrupt occurs, the assembly wrapper at
enrty_32.s jumps the execution at smp_apic_timer_interrupt(). At the
beginning of this function, I've checked to see if interrupts are enabled or
not using irqs_disabled() and I found out that they are disabled.

The problem is that I can't find where Linux disables interrupts before
calling smp_apic_timer_interrupt(). The only place this could be done is in
the assembly wrapper but I can't really find it.

Does the processor disables interrupts by default when a LAPIC timer
interrupt occurs?

Any help will be much appreciated.

Thanks in advance.

John.

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