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Commit 67664c8f authored by Ashok Raj's avatar Ashok Raj Committed by Linus Torvalds
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[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: default avatarAshok Raj <ashok.raj@intel.com>
Acked-by: default avatarShaohua Li <shaohua.li@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent f3705136

arch/i386/mach-default/setup.c

+27 −0
Original line number Diff line number Diff line
@@ -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);

include/asm-i386/mach-default/mach_ipi.h

+25 −2
Original line number Diff line number Diff line
@@ -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(int vector) 
	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 */