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Commit 329d400f authored by Zwane Mwaikambo's avatar Zwane Mwaikambo Committed by Linus Torvalds
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[PATCH] x86_64/i386: Remove preempt disable calls in lowlevel IPI 



I noticed that some lowlevel send_IPI_mask helpers had a hotplug/preempt
race whereupon the cpu_online_map was read before disabling preemption;

...
cpumask_t mask = cpu_online_map;
int cpu = get_cpu();
cpu_clear(cpu, mask);
...

But then i realised that there is no need for these lowlevel functions to
be going through all this trouble when all the callers are already made
hotplug/preempt safe.

Signed-off-by: default avatarZwane Mwaikambo <zwane@arm.linux.org.uk>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 73ca5358

arch/x86_64/kernel/genapic_cluster.c

+1 −4
Original line number Diff line number Diff line
@@ -72,14 +72,11 @@ static void cluster_send_IPI_mask(cpumask_t mask, int vector) 
static void cluster_send_IPI_allbutself(int vector)

{

	cpumask_t mask = cpu_online_map;

	int me = get_cpu(); /* Ensure we are not preempted when we clear */



	cpu_clear(me, mask);

	cpu_clear(smp_processor_id(), mask);



	if (!cpus_empty(mask))

		cluster_send_IPI_mask(mask, vector);



	put_cpu();

}



static void cluster_send_IPI_all(int vector)

arch/x86_64/kernel/genapic_flat.c

+4 −6
Original line number Diff line number Diff line
@@ -83,12 +83,11 @@ static void flat_send_IPI_allbutself(int vector) 
		__send_IPI_shortcut(APIC_DEST_ALLBUT, vector,APIC_DEST_LOGICAL);

#else

	cpumask_t allbutme = cpu_online_map;

	int me = get_cpu(); /* Ensure we are not preempted when we clear */

	cpu_clear(me, allbutme);



	cpu_clear(smp_processor_id(), allbutme);



	if (!cpus_empty(allbutme))

		flat_send_IPI_mask(allbutme, vector);

	put_cpu();

#endif

}
@@ -149,10 +148,9 @@ static void physflat_send_IPI_mask(cpumask_t cpumask, int vector) 
static void physflat_send_IPI_allbutself(int vector)

{

	cpumask_t allbutme = cpu_online_map;

	int me = get_cpu();

	cpu_clear(me, allbutme);



	cpu_clear(smp_processor_id(), allbutme);

	physflat_send_IPI_mask(allbutme, vector);

	put_cpu();

}



static void physflat_send_IPI_all(int vector)

include/asm-i386/mach-default/mach_ipi.h

+1 −3
Original line number Diff line number Diff line
@@ -15,11 +15,9 @@ static inline void __local_send_IPI_allbutself(int vector) 
{

	if (no_broadcast) {

		cpumask_t mask = cpu_online_map;

		int this_cpu = get_cpu();



		cpu_clear(this_cpu, mask);

		cpu_clear(smp_processor_id(), mask);

		send_IPI_mask(mask, vector);

		put_cpu();

	} else

		__send_IPI_shortcut(APIC_DEST_ALLBUT, vector);

}