Commit 3b6f70fd authored May 29, 2012 by Yong Zhang Committed by Thomas Gleixner Jun 05, 2012

x86-smp-remove-call-to-ipi_call_lock-ipi_call_unlock



ipi_call_lock/unlock() lock resp. unlock call_function.lock. This lock
protects only the call_function data structure itself, but it's
completely unrelated to cpu_online_mask. The mask to which the IPIs
are sent is calculated before call_function.lock is taken in
smp_call_function_many(), so the locking around set_cpu_online() is
pointless and can be removed.

[ tglx: Massaged changelog ]

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: ralf@linux-mips.org
Cc: sshtylyov@mvista.com
Cc: david.daney@cavium.com
Cc: nikunj@linux.vnet.ibm.com
Cc: paulmck@linux.vnet.ibm.com
Cc: axboe@kernel.dk
Cc: peterz@infradead.org
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1338275765-3217-7-git-send-email-yong.zhang0@gmail.com


Acked-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 8efdfc3a

arch/x86/kernel/smpboot.c

+0 −9

Original line number	Diff line number	Diff line
		@@ -255,22 +255,13 @@ notrace static void __cpuinit start_secondary(void *unused)
		check_tsc_sync_target();

		/*
		* We need to hold call_lock, so there is no inconsistency
		* between the time smp_call_function() determines number of
		* IPI recipients, and the time when the determination is made
		* for which cpus receive the IPI. Holding this
		* lock helps us to not include this cpu in a currently in progress
		* smp_call_function().
		*
		* We need to hold vector_lock so there the set of online cpus
		* does not change while we are assigning vectors to cpus. Holding
		* this lock ensures we don't half assign or remove an irq from a cpu.
		*/
		ipi_call_lock();
		lock_vector_lock();
		set_cpu_online(smp_processor_id(), true);
		unlock_vector_lock();
		ipi_call_unlock();
		per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
		x86_platform.nmi_init();

arch/x86/xen/smp.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -80,9 +80,7 @@ static void __cpuinit cpu_bringup(void)

		notify_cpu_starting(cpu);

		ipi_call_lock();
		set_cpu_online(cpu, true);
		ipi_call_unlock();

		this_cpu_write(cpu_state, CPU_ONLINE);

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