[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 (file)
--- 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 9da3edb..1a2ab82 100644 (file)
--- 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 cc756a6..a1d0072 100644 (file)
--- 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);
 }