4.4-stable review patch. If anyone has any objections, please let me know.
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From: Lukas Wunner lukas@wunner.de
commit 746a923b863a1065ef77324e1e43f19b1a3eab5c upstream.
Commit 1e77d0a1ed74 ("genirq: Sanitize spurious interrupt detection of threaded irqs") made detection of spurious interrupts work for threaded handlers by:
a) incrementing a counter every time the thread returns IRQ_HANDLED, and b) checking whether that counter has increased every time the thread is woken.
However for oneshot interrupts, the commit unmasks the interrupt before incrementing the counter. If another interrupt occurs right after unmasking but before the counter is incremented, that interrupt is incorrectly considered spurious:
time | irq_thread() | irq_thread_fn() | action->thread_fn() | irq_finalize_oneshot() | unmask_threaded_irq() /* interrupt is unmasked */ | | /* interrupt fires, incorrectly deemed spurious */ | | atomic_inc(&desc->threads_handled); /* counter is incremented */ v
This is observed with a hi3110 CAN controller receiving data at high volume (from a separate machine sending with "cangen -g 0 -i -x"): The controller signals a huge number of interrupts (hundreds of millions per day) and every second there are about a dozen which are deemed spurious.
In theory with high CPU load and the presence of higher priority tasks, the number of incorrectly detected spurious interrupts might increase beyond the 99,900 threshold and cause disablement of the interrupt.
In practice it just increments the spurious interrupt count. But that can cause people to waste time investigating it over and over.
Fix it by moving the accounting before the invocation of irq_finalize_oneshot().
[ tglx: Folded change log update ]
Fixes: 1e77d0a1ed74 ("genirq: Sanitize spurious interrupt detection of threaded irqs") Signed-off-by: Lukas Wunner lukas@wunner.de Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: Mathias Duckeck m.duckeck@kunbus.de Cc: Akshay Bhat akshay.bhat@timesys.com Cc: Casey Fitzpatrick casey.fitzpatrick@timesys.com Cc: stable@vger.kernel.org # v3.16+ Link: https://lkml.kernel.org/r/1dfd8bbd16163940648045495e3e9698e63b50ad.153986704... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/irq/manage.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -864,6 +864,9 @@ irq_forced_thread_fn(struct irq_desc *de
local_bh_disable(); ret = action->thread_fn(action->irq, action->dev_id); + if (ret == IRQ_HANDLED) + atomic_inc(&desc->threads_handled); + irq_finalize_oneshot(desc, action); local_bh_enable(); return ret; @@ -880,6 +883,9 @@ static irqreturn_t irq_thread_fn(struct irqreturn_t ret;
ret = action->thread_fn(action->irq, action->dev_id); + if (ret == IRQ_HANDLED) + atomic_inc(&desc->threads_handled); + irq_finalize_oneshot(desc, action); return ret; } @@ -957,8 +963,6 @@ static int irq_thread(void *data) irq_thread_check_affinity(desc, action);
action_ret = handler_fn(desc, action); - if (action_ret == IRQ_HANDLED) - atomic_inc(&desc->threads_handled); if (action_ret == IRQ_WAKE_THREAD) irq_wake_secondary(desc, action);