[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>

3 files changed, 6 insertions, 13 deletions

diff --git a/arch/x86_64/kernel/genapic_cluster.c b/arch/x86_64/kernel/genapic_cluster.c
index a472d62f899..43fcf62fef0 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_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)
diff --git a/arch/x86_64/kernel/genapic_flat.c b/arch/x86_64/kernel/genapic_flat.c
index 9da3edb799e..1a2ab825be9 100644
--- a/arch/x86_64/kernel/genapic_flat.c
+++ b/arch/x86_64/kernel/genapic_flat.c
@@ -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)
diff --git a/include/asm-i386/mach-default/mach_ipi.h b/include/asm-i386/mach-default/mach_ipi.h
index cc756a67cd6..a1d0072e36b 100644
--- a/include/asm-i386/mach-default/mach_ipi.h
+++ b/include/asm-i386/mach-default/mach_ipi.h
@@ -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);
 }