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Filename Latest commit message Latest commit date
Sultan Alsawaf 04ad505eed drm/i915: Fix ref->mutex deadlock in i915_active_wait()
The following deadlock exists in i915_active_wait() due to a double lock
on ref->mutex (call chain listed in order from top to bottom):
 i915_active_wait();
 mutex_lock_interruptible(&ref->mutex); <-- ref->mutex first acquired
 i915_active_request_retire();
 node_retire();
 active_retire();
 mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING); <-- DEADLOCK

Fix the deadlock by skipping the second ref->mutex lock when
active_retire() is called through i915_active_request_retire().

Note that this bug only affects 5.4 and has since been fixed in 5.5.
Normally, a backport of the fix from 5.5 would be in order, but the
patch set that fixes this deadlock involves massive changes that are
neither feasible nor desirable for backporting [1][2][3]. Therefore,
this small patch was made to address the deadlock specifically for 5.4.

[1] 274cbf20fd10 ("drm/i915: Push the i915_active.retire into a worker")
[2] 093b92287363 ("drm/i915: Split i915_active.mutex into an irq-safe spinlock for the rbtree")
[3] 750bde2fd4ff ("drm/i915: Serialise with remote retirement")

Fixes: 12c255b5da ("drm/i915: Provide an i915_active.acquire callback")
Cc: <stable@vger.kernel.org> # 5.4.x
Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-04-13 10:48:15 +02:00
arch ARM: imx: only select ARM_ERRATA_814220 for ARMv7-A 2020-04-13 10:48:11 +02:00
block blk-mq: Keep set->nr_hw_queues and set->map[].nr_queues in sync 2020-04-13 10:48:14 +02:00
certs
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Documentation
drivers drm/i915: Fix ref->mutex deadlock in i915_active_wait() 2020-04-13 10:48:15 +02:00
fs ceph: canonicalize server path in place 2020-04-13 10:48:11 +02:00
include include/uapi/linux/swab.h: fix userspace breakage, use __BITS_PER_LONG for swap 2020-04-13 10:48:12 +02:00
init
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kernel
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mm slub: improve bit diffusion for freelist ptr obfuscation 2020-04-13 10:48:07 +02:00
net Bluetooth: RFCOMM: fix ODEBUG bug in rfcomm_dev_ioctl 2020-04-13 10:48:13 +02:00
samples
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sound ASoC: jz4740-i2s: Fix divider written at incorrect offset in register 2020-04-13 10:48:09 +02:00
tools tools/accounting/getdelays.c: fix netlink attribute length 2020-04-13 10:48:08 +02:00
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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.

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.