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Commit 20b87691 authored by Christoph Lameter's avatar Christoph Lameter Committed by Tejun Heo
Browse files

irq_work: Use per cpu atomics instead of regular atomics 



The irq work queue is a per cpu object and it is sufficient for
synchronization if per cpu atomics are used. Doing so simplifies
the code and reduces the overhead of the code.

Before:

christoph@linux-2.6$ size kernel/irq_work.o
   text	   data	    bss	    dec	    hex	filename
    451	      8	      1	    460	    1cc	kernel/irq_work.o

After:

christoph@linux-2.6$ size kernel/irq_work.o 
   text	   data	    bss	    dec	    hex	filename
    438	      8	      1	    447	    1bf	kernel/irq_work.o

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarChristoph Lameter <cl@linux.com>
parent 05c2d088

kernel/irq_work.c

+9 −9
Original line number Diff line number Diff line
@@ -77,21 +77,21 @@ void __weak arch_irq_work_raise(void) 
 */

static void __irq_work_queue(struct irq_work *entry)

{

	struct irq_work **head, *next;

	struct irq_work *next;



	head = &get_cpu_var(irq_work_list);

	preempt_disable();



	do {

		next = *head;

		next = __this_cpu_read(irq_work_list);

		/* Can assign non-atomic because we keep the flags set. */

		entry->next = next_flags(next, IRQ_WORK_FLAGS);

	} while (cmpxchg(head, next, entry) != next);

	} while (this_cpu_cmpxchg(irq_work_list, next, entry) != next);



	/* The list was empty, raise self-interrupt to start processing. */

	if (!irq_work_next(entry))

		arch_irq_work_raise();



	put_cpu_var(irq_work_list);

	preempt_enable();

}



/*
@@ -120,16 +120,16 @@ EXPORT_SYMBOL_GPL(irq_work_queue); 
 */

void irq_work_run(void)

{

	struct irq_work *list, **head;

	struct irq_work *list;



	head = &__get_cpu_var(irq_work_list);

	if (*head == NULL)

	if (this_cpu_read(irq_work_list) == NULL)

		return;



	BUG_ON(!in_irq());

	BUG_ON(!irqs_disabled());



	list = xchg(head, NULL);

	list = this_cpu_xchg(irq_work_list, NULL);



	while (list != NULL) {

		struct irq_work *entry = list;