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 <[email protected]>
Acked-by: Shaohua Li <[email protected]>
----------------------------------------------------
arch/i386/mach-default/setup.c | 27 +++++++++++++++++++++++++++
include/asm-i386/mach-default/mach_ipi.h | 27 +++++++++++++++++++++++++--
2 files changed, 52 insertions(+), 2 deletions(-)
Index: linux-2.6.12-rc6-mm1/include/asm-i386/mach-default/mach_ipi.h
===================================================================
--- linux-2.6.12-rc6-mm1.orig/include/asm-i386/mach-default/mach_ipi.h
+++ linux-2.6.12-rc6-mm1/include/asm-i386/mach-default/mach_ipi.h
@@ -4,11 +4,34 @@
void send_IPI_mask_bitmask(cpumask_t mask, int vector);
void __send_IPI_shortcut(unsigned int shortcut, int vector);
+extern int no_broadcast;
+
static inline void send_IPI_mask(cpumask_t mask, int vector)
{
send_IPI_mask_bitmask(mask, vector);
}
+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);
+ send_IPI_mask(mask, vector);
+ put_cpu();
+ } else
+ __send_IPI_shortcut(APIC_DEST_ALLBUT, vector);
+}
+
+static inline void __local_send_IPI_all(int vector)
+{
+ if (no_broadcast)
+ send_IPI_mask(cpu_online_map, vector);
+ else
+ __send_IPI_shortcut(APIC_DEST_ALLINC, vector);
+}
+
static inline void send_IPI_allbutself(int vector)
{
/*
@@ -18,13 +41,13 @@ static inline void send_IPI_allbutself(i
if (!(num_online_cpus() > 1))
return;
- __send_IPI_shortcut(APIC_DEST_ALLBUT, vector);
+ __local_send_IPI_allbutself(vector);
return;
}
static inline void send_IPI_all(int vector)
{
- __send_IPI_shortcut(APIC_DEST_ALLINC, vector);
+ __local_send_IPI_all(vector);
}
#endif /* __ASM_MACH_IPI_H */
Index: linux-2.6.12-rc6-mm1/arch/i386/mach-default/setup.c
===================================================================
--- linux-2.6.12-rc6-mm1.orig/arch/i386/mach-default/setup.c
+++ linux-2.6.12-rc6-mm1/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 @@ void __init mca_nmi_hook(void)
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);
--
-
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