[patch 5/8] x86_64:Dont do broadcast IPIs when hotplug is enabled in flat mode.

[Ashok Raj <ashok.raj@intel.com>]

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 <ashok.raj@intel.com>
-------------------------------------------------------
 arch/x86_64/kernel/genapic_flat.c |    8 ++++++++
 1 files changed, 8 insertions(+)

Index: linux-2.6.13-rc4-mm1/arch/x86_64/kernel/genapic_flat.c
===================================================================
--- linux-2.6.13-rc4-mm1.orig/arch/x86_64/kernel/genapic_flat.c
+++ linux-2.6.13-rc4-mm1/arch/x86_64/kernel/genapic_flat.c
@@ -78,8 +78,16 @@ 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);
+	flat_send_IPI_mask(allbutme, vector);
+	put_cpu();
+#endif
 }
 
 static void flat_send_IPI_all(int vector)

--

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