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authorIdo Yariv <ido@wizery.com>2011-12-02 18:24:12 +0200
committerThomas Gleixner <tglx@linutronix.de>2012-03-14 11:56:20 +0100
commit7140ea1980f2fae9c7aaeac5f6b35317e1389ee6 (patch)
tree7b1021c74dee94b0171db25bc1965555e0e9a9e5 /kernel
parentdf8d291f28aa1e8437c8f7816328a6516379c71b (diff)
downloadlinux-stericsson-7140ea1980f2fae9c7aaeac5f6b35317e1389ee6.tar.gz
genirq: Flush the irq thread on synchronization
The current implementation does not always flush the threaded handler when disabling the irq. In case the irq handler was called, but the threaded handler hasn't started running yet, the interrupt will be flagged as pending, and the handler will not run. This implementation has some issues: First, if the interrupt is a wake source and flagged as pending, the system will not be able to suspend. Second, when quickly disabling and re-enabling the irq, the threaded handler might continue to run after the irq is re-enabled without the irq handler being called first. This might be an unexpected behavior. In addition, it might be counter-intuitive that the threaded handler will not be called even though the irq handler was called and returned IRQ_WAKE_THREAD. Fix this by always waiting for the threaded handler to complete in synchronize_irq(). [ tglx: Massaged comments, added WARN_ONs and the missing IRQTF_RUNTHREAD check in exit_irq_thread() ] Signed-off-by: Ido Yariv <ido@wizery.com> Link: http://lkml.kernel.org/r/1322843052-7166-1-git-send-email-ido@wizery.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/irq/handle.c12
-rw-r--r--kernel/irq/manage.c60
2 files changed, 44 insertions, 28 deletions
diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
index 500aaf67c546..6ff84e6a954c 100644
--- a/kernel/irq/handle.c
+++ b/kernel/irq/handle.c
@@ -110,6 +110,18 @@ static void irq_wake_thread(struct irq_desc *desc, struct irqaction *action)
* threads_oneshot untouched and runs the thread another time.
*/
desc->threads_oneshot |= action->thread_mask;
+
+ /*
+ * We increment the threads_active counter in case we wake up
+ * the irq thread. The irq thread decrements the counter when
+ * it returns from the handler or in the exit path and wakes
+ * up waiters which are stuck in synchronize_irq() when the
+ * active count becomes zero. synchronize_irq() is serialized
+ * against this code (hard irq handler) via IRQS_INPROGRESS
+ * like the finalize_oneshot() code. See comment above.
+ */
+ atomic_inc(&desc->threads_active);
+
wake_up_process(action->thread);
}
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 1786cf7dac54..453feedbb390 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -759,6 +759,13 @@ static irqreturn_t irq_thread_fn(struct irq_desc *desc,
return ret;
}
+static void wake_threads_waitq(struct irq_desc *desc)
+{
+ if (atomic_dec_and_test(&desc->threads_active) &&
+ waitqueue_active(&desc->wait_for_threads))
+ wake_up(&desc->wait_for_threads);
+}
+
/*
* Interrupt handler thread
*/
@@ -771,7 +778,6 @@ static int irq_thread(void *data)
struct irq_desc *desc = irq_to_desc(action->irq);
irqreturn_t (*handler_fn)(struct irq_desc *desc,
struct irqaction *action);
- int wake;
if (force_irqthreads && test_bit(IRQTF_FORCED_THREAD,
&action->thread_flags))
@@ -783,39 +789,30 @@ static int irq_thread(void *data)
current->irq_thread = 1;
while (!irq_wait_for_interrupt(action)) {
+ irqreturn_t action_ret;
irq_thread_check_affinity(desc, action);
- atomic_inc(&desc->threads_active);
+ action_ret = handler_fn(desc, action);
+ if (!noirqdebug)
+ note_interrupt(action->irq, desc, action_ret);
- raw_spin_lock_irq(&desc->lock);
- if (unlikely(irqd_irq_disabled(&desc->irq_data))) {
- /*
- * CHECKME: We might need a dedicated
- * IRQ_THREAD_PENDING flag here, which
- * retriggers the thread in check_irq_resend()
- * but AFAICT IRQS_PENDING should be fine as it
- * retriggers the interrupt itself --- tglx
- */
- desc->istate |= IRQS_PENDING;
- raw_spin_unlock_irq(&desc->lock);
- } else {
- irqreturn_t action_ret;
-
- raw_spin_unlock_irq(&desc->lock);
- action_ret = handler_fn(desc, action);
- if (!noirqdebug)
- note_interrupt(action->irq, desc, action_ret);
- }
-
- wake = atomic_dec_and_test(&desc->threads_active);
-
- if (wake && waitqueue_active(&desc->wait_for_threads))
- wake_up(&desc->wait_for_threads);
+ wake_threads_waitq(desc);
}
- /* Prevent a stale desc->threads_oneshot */
- irq_finalize_oneshot(desc, action, true);
+ /*
+ * This is the regular exit path. __free_irq() is stopping the
+ * thread via kthread_stop() after calling
+ * synchronize_irq(). So neither IRQTF_RUNTHREAD nor the
+ * oneshot mask bit should be set.
+ *
+ * Verify that this is true.
+ */
+ if (WARN_ON(test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags)))
+ wake_threads_waitq(desc);
+
+ if (WARN_ON(desc->threads_oneshot & action->thread_mask))
+ irq_finalize_oneshot(desc, action, true);
/*
* Clear irq_thread. Otherwise exit_irq_thread() would make
@@ -845,6 +842,13 @@ void exit_irq_thread(void)
desc = irq_to_desc(action->irq);
+ /*
+ * If IRQTF_RUNTHREAD is set, we need to decrement
+ * desc->threads_active and wake possible waiters.
+ */
+ if (test_and_clear_bit(IRQTF_RUNTHREAD, &action->thread_flags))
+ wake_threads_waitq(desc);
+
/* Prevent a stale desc->threads_oneshot */
irq_finalize_oneshot(desc, action, true);
}