[3.8.y.z extended stable] Patch "genirq: Sanitize spurious interrupt detection of threaded irqs" has been added to staging queue
Kamal Mostafa
kamal at canonical.com
Mon Jul 21 21:21:27 UTC 2014
This is a note to let you know that I have just added a patch titled
genirq: Sanitize spurious interrupt detection of threaded irqs
to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree
which can be found at:
http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue
This patch is scheduled to be released in version 3.8.13.27.
If you, or anyone else, feels it should not be added to this tree, please
reply to this email.
For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable
Thanks.
-Kamal
------
>From 7dbeba98ab984e8fda7bfff004b69a21e6d083fb Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx at linutronix.de>
Date: Thu, 7 Mar 2013 14:53:45 +0100
Subject: genirq: Sanitize spurious interrupt detection of threaded irqs
commit 1e77d0a1ed7417d2a5a52a7b8d32aea1833faa6c upstream.
Till reported that the spurious interrupt detection of threaded
interrupts is broken in two ways:
- note_interrupt() is called for each action thread of a shared
interrupt line. That's wrong as we are only interested whether none
of the device drivers felt responsible for the interrupt, but by
calling multiple times for a single interrupt line we account
IRQ_NONE even if one of the drivers felt responsible.
- note_interrupt() when called from the thread handler is not
serialized. That leaves the members of irq_desc which are used for
the spurious detection unprotected.
To solve this we need to defer the spurious detection of a threaded
interrupt to the next hardware interrupt context where we have
implicit serialization.
If note_interrupt is called with action_ret == IRQ_WAKE_THREAD, we
check whether the previous interrupt requested a deferred check. If
not, we request a deferred check for the next hardware interrupt and
return.
If set, we check whether one of the interrupt threads signaled
success. Depending on this information we feed the result into the
spurious detector.
If one primary handler of a shared interrupt returns IRQ_HANDLED we
disable the deferred check of irq threads on the same line, as we have
found at least one device driver who cared.
Reported-by: Till Straumann <strauman at slac.stanford.edu>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Tested-by: Austin Schuh <austin at peloton-tech.com>
Cc: Oliver Hartkopp <socketcan at hartkopp.net>
Cc: Wolfgang Grandegger <wg at grandegger.com>
Cc: Pavel Pisa <pisa at cmp.felk.cvut.cz>
Cc: Marc Kleine-Budde <mkl at pengutronix.de>
Cc: linux-can at vger.kernel.org
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1303071450130.22263@ionos
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
include/linux/irqdesc.h | 4 ++
kernel/irq/manage.c | 4 +-
kernel/irq/spurious.c | 106 ++++++++++++++++++++++++++++++++++++++++++++++--
3 files changed, 108 insertions(+), 6 deletions(-)
diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index 623325e..078bc2f 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -27,6 +27,8 @@ struct irq_desc;
* @irq_count: stats field to detect stalled irqs
* @last_unhandled: aging timer for unhandled count
* @irqs_unhandled: stats field for spurious unhandled interrupts
+ * @threads_handled: stats field for deferred spurious detection of threaded handlers
+ * @threads_handled_last: comparator field for deferred spurious detection of theraded handlers
* @lock: locking for SMP
* @affinity_hint: hint to user space for preferred irq affinity
* @affinity_notify: context for notification of affinity changes
@@ -52,6 +54,8 @@ struct irq_desc {
unsigned int irq_count; /* For detecting broken IRQs */
unsigned long last_unhandled; /* Aging timer for unhandled count */
unsigned int irqs_unhandled;
+ atomic_t threads_handled;
+ int threads_handled_last;
raw_spinlock_t lock;
struct cpumask *percpu_enabled;
#ifdef CONFIG_SMP
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index edbe80e..f26e367 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -860,8 +860,8 @@ static int irq_thread(void *data)
irq_thread_check_affinity(desc, action);
action_ret = handler_fn(desc, action);
- if (!noirqdebug)
- note_interrupt(action->irq, desc, action_ret);
+ if (action_ret == IRQ_HANDLED)
+ atomic_inc(&desc->threads_handled);
wake_threads_waitq(desc);
}
diff --git a/kernel/irq/spurious.c b/kernel/irq/spurious.c
index 7b5f012..febcee3c 100644
--- a/kernel/irq/spurious.c
+++ b/kernel/irq/spurious.c
@@ -265,21 +265,119 @@ try_misrouted_irq(unsigned int irq, struct irq_desc *desc,
return action && (action->flags & IRQF_IRQPOLL);
}
+#define SPURIOUS_DEFERRED 0x80000000
+
void note_interrupt(unsigned int irq, struct irq_desc *desc,
irqreturn_t action_ret)
{
if (desc->istate & IRQS_POLL_INPROGRESS)
return;
- /* we get here again via the threaded handler */
- if (action_ret == IRQ_WAKE_THREAD)
- return;
-
if (bad_action_ret(action_ret)) {
report_bad_irq(irq, desc, action_ret);
return;
}
+ /*
+ * We cannot call note_interrupt from the threaded handler
+ * because we need to look at the compound of all handlers
+ * (primary and threaded). Aside of that in the threaded
+ * shared case we have no serialization against an incoming
+ * hardware interrupt while we are dealing with a threaded
+ * result.
+ *
+ * So in case a thread is woken, we just note the fact and
+ * defer the analysis to the next hardware interrupt.
+ *
+ * The threaded handlers store whether they sucessfully
+ * handled an interrupt and we check whether that number
+ * changed versus the last invocation.
+ *
+ * We could handle all interrupts with the delayed by one
+ * mechanism, but for the non forced threaded case we'd just
+ * add pointless overhead to the straight hardirq interrupts
+ * for the sake of a few lines less code.
+ */
+ if (action_ret & IRQ_WAKE_THREAD) {
+ /*
+ * There is a thread woken. Check whether one of the
+ * shared primary handlers returned IRQ_HANDLED. If
+ * not we defer the spurious detection to the next
+ * interrupt.
+ */
+ if (action_ret == IRQ_WAKE_THREAD) {
+ int handled;
+ /*
+ * We use bit 31 of thread_handled_last to
+ * denote the deferred spurious detection
+ * active. No locking necessary as
+ * thread_handled_last is only accessed here
+ * and we have the guarantee that hard
+ * interrupts are not reentrant.
+ */
+ if (!(desc->threads_handled_last & SPURIOUS_DEFERRED)) {
+ desc->threads_handled_last |= SPURIOUS_DEFERRED;
+ return;
+ }
+ /*
+ * Check whether one of the threaded handlers
+ * returned IRQ_HANDLED since the last
+ * interrupt happened.
+ *
+ * For simplicity we just set bit 31, as it is
+ * set in threads_handled_last as well. So we
+ * avoid extra masking. And we really do not
+ * care about the high bits of the handled
+ * count. We just care about the count being
+ * different than the one we saw before.
+ */
+ handled = atomic_read(&desc->threads_handled);
+ handled |= SPURIOUS_DEFERRED;
+ if (handled != desc->threads_handled_last) {
+ action_ret = IRQ_HANDLED;
+ /*
+ * Note: We keep the SPURIOUS_DEFERRED
+ * bit set. We are handling the
+ * previous invocation right now.
+ * Keep it for the current one, so the
+ * next hardware interrupt will
+ * account for it.
+ */
+ desc->threads_handled_last = handled;
+ } else {
+ /*
+ * None of the threaded handlers felt
+ * responsible for the last interrupt
+ *
+ * We keep the SPURIOUS_DEFERRED bit
+ * set in threads_handled_last as we
+ * need to account for the current
+ * interrupt as well.
+ */
+ action_ret = IRQ_NONE;
+ }
+ } else {
+ /*
+ * One of the primary handlers returned
+ * IRQ_HANDLED. So we don't care about the
+ * threaded handlers on the same line. Clear
+ * the deferred detection bit.
+ *
+ * In theory we could/should check whether the
+ * deferred bit is set and take the result of
+ * the previous run into account here as
+ * well. But it's really not worth the
+ * trouble. If every other interrupt is
+ * handled we never trigger the spurious
+ * detector. And if this is just the one out
+ * of 100k unhandled ones which is handled
+ * then we merily delay the spurious detection
+ * by one hard interrupt. Not a real problem.
+ */
+ desc->threads_handled_last &= ~SPURIOUS_DEFERRED;
+ }
+ }
+
if (unlikely(action_ret == IRQ_NONE)) {
/*
* If we are seeing only the odd spurious IRQ caused by
--
1.9.1
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