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Commit 5234ffb9 authored by Alexander Gordeev's avatar Alexander Gordeev Committed by Thomas Gleixner
Browse files

genirq: Get rid of unnecessary IRQTF_DIED flag 



Currently IRQTF_DIED flag is set when a IRQ thread handler calls do_exit()
But also PF_EXITING per process flag gets set when a thread exits. This
fix eliminates the duplicate by using PF_EXITING flag.

Also, there is a race condition in exit_irq_thread(). In case a thread's
bit is cleared in desc->threads_oneshot (and the IRQ line gets unmasked),
but before IRQTF_DIED flag is set, a new interrupt might come in and set
just cleared bit again, this time forever. This fix throws IRQTF_DIED flag
away, eliminating the race as a result.

[ tglx: Test THREAD_EXITING first as suggested by Oleg ]

Reported-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAlexander Gordeev <agordeev@redhat.com>
Link: http://lkml.kernel.org/r/20120309135958.GD2114@dhcp-26-207.brq.redhat.com


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 05d74efa

kernel/exit.c

+2 −2
Original line number Diff line number Diff line
@@ -935,8 +935,6 @@ void do_exit(long code) 
		schedule();

	}



	exit_irq_thread();



	exit_signals(tsk);  /* sets PF_EXITING */

	/*

	 * tsk->flags are checked in the futex code to protect against
@@ -945,6 +943,8 @@ void do_exit(long code) 
	smp_mb();

	raw_spin_unlock_wait(&tsk->pi_lock);



	exit_irq_thread();



	if (unlikely(in_atomic()))

		printk(KERN_INFO "note: %s[%d] exited with preempt_count %d\n",

				current->comm, task_pid_nr(current),

kernel/irq/handle.c

+1 −1
Original line number Diff line number Diff line
@@ -60,7 +60,7 @@ static void irq_wake_thread(struct irq_desc *desc, struct irqaction *action) 
	 * device interrupt, so no irq storm is lurking. If the

	 * RUNTHREAD bit is already set, nothing to do.

	 */

	if (test_bit(IRQTF_DIED, &action->thread_flags) ||

	if ((action->thread->flags & PF_EXITING) ||

	    test_and_set_bit(IRQTF_RUNTHREAD, &action->thread_flags))

		return;

kernel/irq/internals.h

+0 −2
Original line number Diff line number Diff line
@@ -20,14 +20,12 @@ extern bool noirqdebug; 
/*

 * Bits used by threaded handlers:

 * IRQTF_RUNTHREAD - signals that the interrupt handler thread should run

 * IRQTF_DIED      - handler thread died

 * IRQTF_WARNED    - warning "IRQ_WAKE_THREAD w/o thread_fn" has been printed

 * IRQTF_AFFINITY  - irq thread is requested to adjust affinity

 * IRQTF_FORCED_THREAD  - irq action is force threaded

 */

enum {

	IRQTF_RUNTHREAD,

	IRQTF_DIED,

	IRQTF_WARNED,

	IRQTF_AFFINITY,

	IRQTF_FORCED_THREAD,

kernel/irq/manage.c

+1 −10
Original line number Diff line number Diff line
@@ -845,17 +845,8 @@ void exit_irq_thread(void) 


	desc = irq_to_desc(action->irq);



	/*

	 * Prevent a stale desc->threads_oneshot. Must be called

	 * before setting the IRQTF_DIED flag.

	 */

	/* Prevent a stale desc->threads_oneshot */

	irq_finalize_oneshot(desc, action, true);



	/*

	 * Set the THREAD DIED flag to prevent further wakeups of the

	 * soon to be gone threaded handler.

	 */

	set_bit(IRQTF_DIED, &action->flags);

}



static void irq_setup_forced_threading(struct irqaction *new)