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authorLukas Wunner <lukas@wunner.de>2018-10-18 15:15:05 +0200
committerThomas Gleixner <tglx@linutronix.de>2018-10-19 17:31:00 +0200
commit746a923b863a1065ef77324e1e43f19b1a3eab5c (patch)
tree428e242554fd8e8ded119f6a01b100d7b4c4f9a2 /kernel/irq
parente45506ac0af9b56b221863e9649fe122d8bb42ff (diff)
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genirq: Fix race on spurious interrupt detection
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.1539867047.git.lukas@wunner.de
Diffstat (limited to 'kernel/irq')
-rw-r--r--kernel/irq/manage.c8
1 files changed, 6 insertions, 2 deletions
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index fb86146037a7..9dbdccab3b6a 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -927,6 +927,9 @@ irq_forced_thread_fn(struct irq_desc *desc, struct irqaction *action)
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;
@@ -943,6 +946,9 @@ static irqreturn_t irq_thread_fn(struct irq_desc *desc,
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;
}
@@ -1020,8 +1026,6 @@ 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);