android/android_kernel_asus_sm8350
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[PATCH] x86_64/i386: Remove preempt disable calls in lowlevel IPI

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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: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Zwane Mwaikambo 2006-01-11 22:43:09 +01:00 committed by Linus Torvalds
parent 73ca5358aa
commit 329d400f47
3 changed files with 6 additions and 13 deletions
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5
arch/x86_64/kernel/genapic_cluster.c
View File

@ -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)

10
arch/x86_64/kernel/genapic_flat.c
View File

@ -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)

4
include/asm-i386/mach-default/mach_ipi.h
View File

@ -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);
}