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Commit 37ee16ae authored by Russell King's avatar Russell King Committed by Russell King
Browse files

[ARM SMP] Add core ARM support for local timers 



Add infrastructure for supporting per-cpu local timers to update
the profiling information and update system time accounting.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 3b6353fa

arch/arm/Kconfig

+10 −0
Original line number Diff line number Diff line
@@ -356,6 +356,16 @@ config HOTPLUG_CPU 
	  Say Y here to experiment with turning CPUs off and on.  CPUs

	  can be controlled through /sys/devices/system/cpu.



config LOCAL_TIMERS

	bool "Use local timer interrupts"

	depends on SMP && n

	default y

	help

	  Enable support for local timers on SMP platforms, rather then the

	  legacy IPI broadcast method.  Local timers allows the system

	  accounting to be spread across the timer interval, preventing a

	  "thundering herd" at every timer tick.



config PREEMPT

	bool "Preemptible Kernel (EXPERIMENTAL)"

	depends on EXPERIMENTAL

arch/arm/kernel/entry-armv.S

+7 −0
Original line number Diff line number Diff line
@@ -47,6 +47,13 @@ 
	movne	r0, sp

	adrne	lr, 1b

	bne	do_IPI



#ifdef CONFIG_LOCAL_TIMERS

	test_for_ltirq r0, r6, r5, lr

	movne	r0, sp

	adrne	lr, 1b

	bne	do_local_timer

#endif

#endif



	.endm

arch/arm/kernel/irq.c

+1 −0
Original line number Diff line number Diff line
@@ -264,6 +264,7 @@ int show_interrupts(struct seq_file *p, void *v) 
#endif

#ifdef CONFIG_SMP

		show_ipi_list(p);

		show_local_irqs(p);

#endif

		seq_printf(p, "Err: %10lu\n", irq_err_count);

	}

arch/arm/kernel/smp.c

+34 −0
Original line number Diff line number Diff line
@@ -184,6 +184,11 @@ int __cpuexit __cpu_disable(void) 
	 */

	migrate_irqs();



	/*

	 * Stop the local timer for this CPU.

	 */

	local_timer_stop(cpu);



	/*

	 * Flush user cache and TLB mappings, and then remove this CPU

	 * from the vm mask set of all processes.
@@ -289,6 +294,11 @@ asmlinkage void __cpuinit secondary_start_kernel(void) 
	 */

	cpu_set(cpu, cpu_online_map);



	/*

	 * Setup local timer for this CPU.

	 */

	local_timer_setup(cpu);



	/*

	 * OK, it's off to the idle thread for us

	 */
@@ -454,6 +464,18 @@ void show_ipi_list(struct seq_file *p) 
	seq_putc(p, '\n');

}



void show_local_irqs(struct seq_file *p)

{

	unsigned int cpu;



	seq_printf(p, "LOC: ");



	for_each_present_cpu(cpu)

		seq_printf(p, "%10u ", irq_stat[cpu].local_timer_irqs);



	seq_putc(p, '\n');

}



static void ipi_timer(struct pt_regs *regs)

{

	int user = user_mode(regs);
@@ -464,6 +486,18 @@ static void ipi_timer(struct pt_regs *regs) 
	irq_exit();

}



#ifdef CONFIG_LOCAL_TIMERS

asmlinkage void do_local_timer(struct pt_regs *regs)

{

	int cpu = smp_processor_id();



	if (local_timer_ack()) {

		irq_stat[cpu].local_timer_irqs++;

		ipi_timer(regs);

	}

}

#endif



/*

 * ipi_call_function - handle IPI from smp_call_function()

 *

include/asm-arm/hardirq.h

+1 −0
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 


typedef struct {

	unsigned int __softirq_pending;

	unsigned int local_timer_irqs;

} ____cacheline_aligned irq_cpustat_t;



#include <linux/irq_cpustat.h>	/* Standard mappings for irq_cpustat_t above */