x86_64/i386: Remove preempt disable calls in lowlevel IPI From: Zwane Mwaikambo 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 Signed-off-by: Andi Kleen arch/x86_64/kernel/genapic_cluster.c | 5 +---- arch/x86_64/kernel/genapic_flat.c | 10 ++++------ include/asm-i386/mach-default/mach_ipi.h | 4 +--- 3 files changed, 6 insertions(+), 13 deletions(-) Index: linux/arch/x86_64/kernel/genapic_cluster.c =================================================================== --- linux.orig/arch/x86_64/kernel/genapic_cluster.c +++ linux/arch/x86_64/kernel/genapic_cluster.c @@ -72,14 +72,11 @@ static void cluster_send_IPI_mask(cpumas 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) Index: linux/arch/x86_64/kernel/genapic_flat.c =================================================================== --- linux.orig/arch/x86_64/kernel/genapic_flat.c +++ linux/arch/x86_64/kernel/genapic_flat.c @@ -83,12 +83,11 @@ static void flat_send_IPI_allbutself(int __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(cpuma 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) Index: linux/include/asm-i386/mach-default/mach_ipi.h =================================================================== --- linux.orig/include/asm-i386/mach-default/mach_ipi.h +++ linux/include/asm-i386/mach-default/mach_ipi.h @@ -15,11 +15,9 @@ static inline void __local_send_IPI_allb { 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); }