Commit bf18525f authored by Stephen Boyd's avatar Stephen Boyd Committed by Russell King
Browse files

ARM: 7872/1: Support arch_irq_work_raise() via self IPIs 



By default, IRQ work is run from the tick interrupt (see
irq_work_run() in update_process_times()). When we're in full
NOHZ mode, restarting the tick requires the use of IRQ work and
if the only place we run IRQ work is in the tick interrupt we
have an unbreakable cycle. Implement arch_irq_work_raise() via
self IPIs to break this cycle and get the tick started again.
Note that we implement this via IPIs which are only available on
SMP builds. This shouldn't be a problem because full NOHZ is only
supported on SMP builds anyway.

Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
Reviewed-by: default avatarKevin Hilman <khilman@linaro.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent 8d451442

arch/arm/include/asm/hardirq.h

+1 −1
Original line number Diff line number Diff line
@@ -5,7 +5,7 @@ 
#include <linux/threads.h>

#include <asm/irq.h>



#define NR_IPI	6

#define NR_IPI	7



typedef struct {

	unsigned int __softirq_pending;

arch/arm/kernel/smp.c

+18 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 
#include <linux/clockchips.h>

#include <linux/completion.h>

#include <linux/cpufreq.h>

#include <linux/irq_work.h>



#include <linux/atomic.h>

#include <asm/smp.h>
@@ -66,6 +67,7 @@ enum ipi_msg_type { 
	IPI_CALL_FUNC,

	IPI_CALL_FUNC_SINGLE,

	IPI_CPU_STOP,

	IPI_IRQ_WORK,

};



static DECLARE_COMPLETION(cpu_running);
@@ -448,6 +450,13 @@ void arch_send_call_function_single_ipi(int cpu) 
	smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE);

}



#ifdef CONFIG_IRQ_WORK

void arch_irq_work_raise(void)

{

	smp_cross_call(cpumask_of(smp_processor_id()), IPI_IRQ_WORK);

}

#endif



static const char *ipi_types[NR_IPI] = {

#define S(x,s)	[x] = s

	S(IPI_WAKEUP, "CPU wakeup interrupts"),
@@ -456,6 +465,7 @@ static const char *ipi_types[NR_IPI] = { 
	S(IPI_CALL_FUNC, "Function call interrupts"),

	S(IPI_CALL_FUNC_SINGLE, "Single function call interrupts"),

	S(IPI_CPU_STOP, "CPU stop interrupts"),

	S(IPI_IRQ_WORK, "IRQ work interrupts"),

};



void show_ipi_list(struct seq_file *p, int prec)
@@ -565,6 +575,14 @@ void handle_IPI(int ipinr, struct pt_regs *regs) 
		irq_exit();

		break;



#ifdef CONFIG_IRQ_WORK

	case IPI_IRQ_WORK:

		irq_enter();

		irq_work_run();

		irq_exit();

		break;

#endif



	default:

		printk(KERN_CRIT "CPU%u: Unknown IPI message 0x%x\n",

		       cpu, ipinr);

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