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Chris Wilson df9f85d858 drm/i915: Serialise i915_active_fence_set() with itself 
The expected downside to commit 58b4c1a07a ("drm/i915: Reduce nested
prepare_remote_context() to a trylock") was that it would need to return
-EAGAIN to userspace in order to resolve potential mutex inversion. Such
an unsightly round trip is unnecessary if we could atomically insert a
barrier into the i915_active_fence, so make it happen.

Currently, we use the timeline->mutex (or some other named outer lock)
to order insertion into the i915_active_fence (and so individual nodes
of i915_active). Inside __i915_active_fence_set, we only need then
serialise with the interrupt handler in order to claim the timeline for
ourselves.

However, if we remove the outer lock, we need to ensure the order is
intact between not only multiple threads trying to insert themselves
into the timeline, but also with the interrupt handler completing the
previous occupant. We use xchg() on insert so that we have an ordered
sequence of insertions (and each caller knows the previous fence on
which to wait, preserving the chain of all fences in the timeline), but
we then have to cmpxchg() in the interrupt handler to avoid overwriting
the new occupant. The only nasty side-effect is having to temporarily
strip off the RCU-annotations to apply the atomic operations, otherwise
the rules are much more conventional!

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=112402
Fixes: 58b4c1a07a ("drm/i915: Reduce nested prepare_remote_context() to a trylock")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191127134527.3438410-1-chris@chris-wilson.co.uk
2019-11-27 17:02:14 +00:00
arch ARM: SoC fixes 2019-11-10 13:41:59 -08:00
block blkcg: make blkcg_print_stat() print stats only for online blkgs 2019-11-06 17:08:38 -07:00
certs
crypto Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-09-28 08:14:15 -07:00
Documentation Merge tag 'drm-next-5.5-2019-11-08' of git://people.freedesktop.org/~agd5f/linux into drm-next 2019-11-14 08:43:07 +10:00
drivers drm/i915: Serialise i915_active_fence_set() with itself 2019-11-27 17:02:14 +00:00
fs configfs regression fix for 5.4-rc 2019-11-10 12:59:34 -08:00
include Merge tag 'topic/drm-mipi-dsi-dsc-updates-2019-11-11' of git://anongit.freedesktop.org/drm/drm-intel into drm-intel-next-queued 2019-11-20 15:54:38 +02:00
init Merge branch 'next-lockdown' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-09-28 08:14:15 -07:00
ipc
kernel Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-10 12:03:58 -08:00
lib lib: Remove select of inexistant GENERIC_IO 2019-11-10 10:38:43 -08:00
LICENSES
mm mm: memcontrol: fix network errors from failing __GFP_ATOMIC charges 2019-11-06 08:47:50 -08:00
net vsock/virtio: fix sock refcnt holding during the shutdown 2019-11-08 12:17:50 -08:00
samples samples/bpf: fix build by setting HAVE_ATTR_TEST to zero 2019-10-31 21:39:15 +01:00
scripts Modules fixes for v5.4-rc7 2019-11-08 09:48:19 -08:00
security Linux 5.4-rc7 2019-11-14 05:53:10 +10:00
sound ASoC: Fixes for v5.4 2019-11-07 13:52:17 +01:00
tools Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-11-10 11:55:53 -08:00
usr kbuild: update compile-test header list for v5.4-rc2 2019-10-05 15:29:49 +09:00
virt kvm: call kvm_arch_destroy_vm if vm creation fails 2019-10-31 12:13:16 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild
Kconfig
MAINTAINERS Linux 5.4-rc7 2019-11-14 05:53:10 +10:00
Makefile Linux 5.4-rc7 2019-11-10 16:17:15 -08:00
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.

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.