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Filename Latest commit message Latest commit date
Lukas Wunner 746a923b86 genirq: Fix race on spurious interrupt detection 
Commit 1e77d0a1ed ("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: 1e77d0a1ed ("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
2018-10-19 17:31:00 +02:00
arch Merge tag 'irqchip-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/core 2018-10-06 15:45:07 +02:00
block blk-mq: I/O and timer unplugs are inverted in blktrace 2018-09-27 13:12:44 -06:00
certs
crypto
Documentation Merge tag 'irqchip-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/core 2018-10-06 15:45:07 +02:00
drivers Merge tag 'irqchip-4.20' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/core 2018-10-06 15:45:07 +02:00
firmware
fs filesystem-dax for 4.19-rc6 2018-09-30 06:19:38 -07:00
include genirq: Fix grammar s/an /a / 2018-10-09 07:50:41 +02:00
init
ipc
kernel genirq: Fix race on spurious interrupt detection 2018-10-19 17:31:00 +02:00
lib
LICENSES
mm
net ip_tunnel: be careful when accessing the inner header 2018-09-24 12:27:04 -07:00
samples
scripts
security Revert "uapi/linux/keyctl.h: don't use C++ reserved keyword as a struct member name" 2018-09-25 13:28:58 +02:00
sound
tools powerpc fixes for 4.19 #3 2018-09-28 17:43:32 -07:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS A trivial fix for auxdisplay 2018-09-30 06:20:33 -07:00
Makefile Linux 4.19-rc6 2018-09-30 07:15:35 -07:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.