[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: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/x86_64/kernel/genapic_cluster.c b/arch/x86_64/kernel/genapic_cluster.c
index a472d62..43fcf62 100644
--- a/arch/x86_64/kernel/genapic_cluster.c
+++ b/arch/x86_64/kernel/genapic_cluster.c
@@ -72,14 +72,11 @@
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)
diff --git a/arch/x86_64/kernel/genapic_flat.c b/arch/x86_64/kernel/genapic_flat.c
index 9da3edb..1a2ab82 100644
--- a/arch/x86_64/kernel/genapic_flat.c
+++ b/arch/x86_64/kernel/genapic_flat.c
@@ -83,12 +83,11 @@
__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_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)
diff --git a/include/asm-i386/mach-default/mach_ipi.h b/include/asm-i386/mach-default/mach_ipi.h
index cc756a6..a1d0072 100644
--- a/include/asm-i386/mach-default/mach_ipi.h
+++ b/include/asm-i386/mach-default/mach_ipi.h
@@ -15,11 +15,9 @@
{
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);
}