From: Ashok Raj The use of non-shortcut version of routines breaking CPU hotplug. The option to select this via cmdline also is deleted with the physflat patch, hence directly placing this code under CONFIG_HOTPLUG_CPU. We dont want to use broadcast mode IPI's when hotplug is enabled. This causes bad effects in send IPI to a cpu that is offline which can trip when the cpu is in the process of being kicked alive. Signed-off-by: Ashok Raj Cc: Andi Kleen Signed-off-by: Andrew Morton --- arch/x86_64/kernel/genapic_flat.c | 10 ++++++++++ 1 files changed, 10 insertions(+) diff -puN arch/x86_64/kernel/genapic_flat.c~x86_64dont-do-broadcast-ipis-when-hotplug-is-enabled-in-flat-mode arch/x86_64/kernel/genapic_flat.c --- devel/arch/x86_64/kernel/genapic_flat.c~x86_64dont-do-broadcast-ipis-when-hotplug-is-enabled-in-flat-mode 2005-08-04 10:42:08.000000000 -0700 +++ devel-akpm/arch/x86_64/kernel/genapic_flat.c 2005-08-04 10:42:08.000000000 -0700 @@ -78,8 +78,18 @@ static void flat_send_IPI_mask(cpumask_t static void flat_send_IPI_allbutself(int vector) { +#ifndef CONFIG_HOTPLUG_CPU if (((num_online_cpus()) - 1) >= 1) __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); + + if (!cpus_empty(allbutme)) + flat_send_IPI_mask(allbutme, vector); + put_cpu(); +#endif } static void flat_send_IPI_all(int vector) _