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genirq: Get rid of unnecessary IRQTF_DIED flag

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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: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Alexander Gordeev <agordeev@redhat.com>
Link: http://lkml.kernel.org/r/20120309135958.GD2114@dhcp-26-207.brq.redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Alexander Gordeev 2012-03-09 14:59:59 +01:00 committed by Thomas Gleixner
parent 05d74efa3c
commit 5234ffb9f7
4 changed files with 4 additions and 15 deletions
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4
kernel/exit.c
View File

@ -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),

2
kernel/irq/handle.c
View File

@ -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;

2
kernel/irq/internals.h
View File

@ -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,

11
kernel/irq/manage.c
View File

@ -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)