[PATCH] i386: Dont use IPI broadcast when using cpu hotplug.
This patch introduces a startup parameter no_broadcast. When we enable
CONFIG_HOTPLUG_CPU, we dont want to use broadcast shortcut as it has ill
effects on a offline cpu. If we issue broadcast, the IPI is also delivered
to offline cpus, or partially up cpu causing stale IPI's to be handled,
which is a problem and can cause undesirable effects.
Introduces a new startup cmdline option no_ipi_broadcast, that can be
switched at cmdline if necessary.
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Acked-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/i386/mach-default/setup.c b/arch/i386/mach-default/setup.c
index 0aa08ea..e5a1a83 100644
--- a/arch/i386/mach-default/setup.c
+++ b/arch/i386/mach-default/setup.c
@@ -10,6 +10,14 @@
#include <asm/acpi.h>
#include <asm/arch_hooks.h>
+#ifdef CONFIG_HOTPLUG_CPU
+#define DEFAULT_SEND_IPI (1)
+#else
+#define DEFAULT_SEND_IPI (0)
+#endif
+
+int no_broadcast=DEFAULT_SEND_IPI;
+
/**
* pre_intr_init_hook - initialisation prior to setting up interrupt vectors
*
@@ -104,3 +112,22 @@
printk("NMI generated from unknown source!\n");
}
#endif
+
+static __init int no_ipi_broadcast(char *str)
+{
+ get_option(&str, &no_broadcast);
+ printk ("Using %s mode\n", no_broadcast ? "No IPI Broadcast" :
+ "IPI Broadcast");
+ return 1;
+}
+
+__setup("no_ipi_broadcast", no_ipi_broadcast);
+
+static int __init print_ipi_mode(void)
+{
+ printk ("Using IPI %s mode\n", no_broadcast ? "No-Shortcut" :
+ "Shortcut");
+ return 0;
+}
+
+late_initcall(print_ipi_mode);