94 lines
3.2 KiB
Diff
94 lines
3.2 KiB
Diff
From: Thomas Gleixner <tglx@linutronix.de>
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Date: Tue Mar 6 23:18:54 2012 +0100
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Subject: genirq: Clear action->thread_mask if IRQ_ONESHOT is not set
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commit ac5637611(genirq: Unmask oneshot irqs when thread was not woken)
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fails to unmask when a !IRQ_ONESHOT threaded handler is handled by
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handle_level_irq.
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This happens because thread_mask is or'ed unconditionally in
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irq_wake_thread(), but for !IRQ_ONESHOT interrupts never cleared. So
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the check for !desc->thread_active fails and keeps the interrupt
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disabled.
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Keep the thread_mask zero for !IRQ_ONESHOT interrupts.
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Document the thread_mask magic while at it.
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[ commit 52abb700e16a9aa4cbc03f3d7f80206cbbc80680 upstream ]
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Reported-and-tested-by: Sven Joachim <svenjoac@gmx.de>
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Reported-and-tested-by: Stefan Lippers-Hollmann <s.l-h@gmx.de>
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Cc: stable@vger.kernel.org
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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---
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kernel/irq/manage.c | 44 ++++++++++++++++++++++++++++++++++++++------
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1 file changed, 38 insertions(+), 6 deletions(-)
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Index: linux-3.2/kernel/irq/manage.c
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===================================================================
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--- linux-3.2.orig/kernel/irq/manage.c
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+++ linux-3.2/kernel/irq/manage.c
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@@ -985,6 +985,11 @@ __setup_irq(unsigned int irq, struct irq
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/* add new interrupt at end of irq queue */
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do {
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+ /*
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+ * Or all existing action->thread_mask bits,
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+ * so we can find the next zero bit for this
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+ * new action.
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+ */
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thread_mask |= old->thread_mask;
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old_ptr = &old->next;
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old = *old_ptr;
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@@ -993,14 +998,41 @@ __setup_irq(unsigned int irq, struct irq
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}
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/*
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- * Setup the thread mask for this irqaction. Unlikely to have
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- * 32 resp 64 irqs sharing one line, but who knows.
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+ * Setup the thread mask for this irqaction for ONESHOT. For
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+ * !ONESHOT irqs the thread mask is 0 so we can avoid a
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+ * conditional in irq_wake_thread().
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*/
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- if (new->flags & IRQF_ONESHOT && thread_mask == ~0UL) {
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- ret = -EBUSY;
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- goto out_mask;
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+ if (new->flags & IRQF_ONESHOT) {
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+ /*
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+ * Unlikely to have 32 resp 64 irqs sharing one line,
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+ * but who knows.
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+ */
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+ if (thread_mask == ~0UL) {
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+ ret = -EBUSY;
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+ goto out_mask;
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+ }
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+ /*
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+ * The thread_mask for the action is or'ed to
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+ * desc->thread_active to indicate that the
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+ * IRQF_ONESHOT thread handler has been woken, but not
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+ * yet finished. The bit is cleared when a thread
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+ * completes. When all threads of a shared interrupt
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+ * line have completed desc->threads_active becomes
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+ * zero and the interrupt line is unmasked. See
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+ * handle.c:irq_wake_thread() for further information.
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+ *
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+ * If no thread is woken by primary (hard irq context)
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+ * interrupt handlers, then desc->threads_active is
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+ * also checked for zero to unmask the irq line in the
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+ * affected hard irq flow handlers
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+ * (handle_[fasteoi|level]_irq).
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+ *
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+ * The new action gets the first zero bit of
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+ * thread_mask assigned. See the loop above which or's
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+ * all existing action->thread_mask bits.
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+ */
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+ new->thread_mask = 1 << ffz(thread_mask);
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}
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- new->thread_mask = 1 << ffz(thread_mask);
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if (!shared) {
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init_waitqueue_head(&desc->wait_for_threads);
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