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author | Dave Airlie <airlied@redhat.com> | 2013-11-08 06:34:39 (GMT) |
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committer | Dave Airlie <airlied@redhat.com> | 2013-11-08 06:34:39 (GMT) |
commit | 91915260ea5ed9d9b19bfb75d53c989c8ada2ab0 (patch) | |
tree | f7eb16ced65f39ebd0bb32e3b4e5e0f365755536 /kernel/events/ring_buffer.c | |
parent | 21136946c495b0e1e0f7e25a8de6f170efbdeadf (diff) | |
parent | 07bf139b906013ecef0c5e0441564d1ae10e974a (diff) | |
download | linux-91915260ea5ed9d9b19bfb75d53c989c8ada2ab0.tar.xz |
Merge tag 'drm-intel-fixes-2013-11-07' of git://people.freedesktop.org/~danvet/drm-intel into drm-next
Bit a bit -fixes pull request in the merge window than usual dua to two
feauture-y things:
- Display CRCs are now enabled on all platforms, including the odd DP case
on gm45/vlv. Since this is a testing-only feature it should ever hurt,
but I figured it'll help with regression-testing -fixes. So I left it
in and didn't postpone it to 3.14.
- Display power well refactoring from Imre. Would have caused major pain
conflict with the bdw stage 1 patches if I'd postpone this to -next.
It's only an relatively small interface rework, so shouldn't cause pain.
It's also been in my tree since almost 3 weeks already.
That accounts for about two thirds of the pull, otherwise just bugfixes:
- vlv backlight fix from Jesse/Jani
- vlv vblank timestamp fix from Jesse
- improved edp detection through vbt from Ville (fixes a vlv issue)
- eDP vdd fix from Paulo
- fixes for dvo lvds on i830M
- a few smaller things all over
Note: This contains a backmerge of v3.12. Since the -internal branch
always applied on top of -nightly I need that unified base to merge bdw
patches. So you'll get a conflict with radeon connector props when pulling
this (and nouveau/master will also conflict a bit when Ben doesn't
rebase). The backmerge itself only had conflicts in drm/i915.
There's also a tiny conflict between Jani's backlight fix and your sysfs
lifetime fix in drm-next.
* tag 'drm-intel-fixes-2013-11-07' of git://people.freedesktop.org/~danvet/drm-intel: (940 commits)
drm/i915/vlv: use per-pipe backlight controls v2
drm/i915: make backlight functions take a connector
drm/i915: move opregion asle request handling to a work queue
drm/i915/vlv: use PIPE_START_VBLANK interrupts on VLV
drm/i915: Make intel_dp_is_edp() less specific
drm/i915: Give names to the VBT child device type bits
drm/i915/vlv: enable HDA display audio for Valleyview2
drm/i915/dvo: call ->mode_set callback only when the port is running
drm/i915: avoid unclaimed registers when capturing the error state
drm/i915: Enable DP port CRC for the "auto" source on g4x/vlv
drm/i915: scramble reset support for DP port CRC on vlv
drm/i915: scramble reset support for DP port CRC on g4x
drm/i916: add "auto" pipe CRC source
...
Conflicts:
MAINTAINERS
drivers/gpu/drm/i915/intel_panel.c
drivers/gpu/drm/nouveau/core/subdev/mc/base.c
drivers/gpu/drm/radeon/atombios_encoders.c
drivers/gpu/drm/radeon/radeon_connectors.c
Diffstat (limited to 'kernel/events/ring_buffer.c')
-rw-r--r-- | kernel/events/ring_buffer.c | 31 |
1 files changed, 27 insertions, 4 deletions
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index cd55144..9c2ddfb 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -87,10 +87,31 @@ again: goto out; /* - * Publish the known good head. Rely on the full barrier implied - * by atomic_dec_and_test() order the rb->head read and this - * write. + * Since the mmap() consumer (userspace) can run on a different CPU: + * + * kernel user + * + * READ ->data_tail READ ->data_head + * smp_mb() (A) smp_rmb() (C) + * WRITE $data READ $data + * smp_wmb() (B) smp_mb() (D) + * STORE ->data_head WRITE ->data_tail + * + * Where A pairs with D, and B pairs with C. + * + * I don't think A needs to be a full barrier because we won't in fact + * write data until we see the store from userspace. So we simply don't + * issue the data WRITE until we observe it. Be conservative for now. + * + * OTOH, D needs to be a full barrier since it separates the data READ + * from the tail WRITE. + * + * For B a WMB is sufficient since it separates two WRITEs, and for C + * an RMB is sufficient since it separates two READs. + * + * See perf_output_begin(). */ + smp_wmb(); rb->user_page->data_head = head; /* @@ -154,9 +175,11 @@ int perf_output_begin(struct perf_output_handle *handle, * Userspace could choose to issue a mb() before updating the * tail pointer. So that all reads will be completed before the * write is issued. + * + * See perf_output_put_handle(). */ tail = ACCESS_ONCE(rb->user_page->data_tail); - smp_rmb(); + smp_mb(); offset = head = local_read(&rb->head); head += size; if (unlikely(!perf_output_space(rb, tail, offset, head))) |