[Bug 97396] New: [drm] stuck on bsd ring (bisected)

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https://bugs.freedesktop.org/show_bug.cgi?id=97396

            Bug ID: 97396
           Summary: [drm] stuck on bsd ring (bisected)
           Product: DRI
           Version: XOrg git
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: minor
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: mymailclone at t-online.de
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Since kernel 4.3 and up to 4.7.1, dmesg shows the following or similar messages
after resuming from hibernation, here for 4.7.1:

[drm] stuck on bsd ring
[drm] GPU HANG: ecode 5:2:0x01000000, reason: Engine(s) hung, action: reset
[drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including
userspace.
[drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI ->
DRM/Intel
[drm] drm/i915 developers can then reassign to the right component if it's not
a kernel issue.
[drm] The gpu crash dump is required to analyze gpu hangs, so please always
attach it.
[drm] GPU crash dump saved to /sys/class/drm/card0/error
drm/i915: Resetting chip after gpu hang

Interestingly, with 4.4.18 I only see this:

[drm] stuck on bsd ring
[drm] GPU HANG: ecode 5:1:0x01000000, reason: Ring hung, action: reset
drm/i915: Resetting chip after gpu hang

Other than the messages, I haven't noticed any negative impact on my system
(Core i3). But this may be different for other setups (see
https://bugs.freedesktop.org/show_bug.cgi?id=94203). 

I bisected between 4.2 and 4.3, "bad/good" strictly according to whether "[drm]
stuck on bsd ring" occurred or not - disregarding all the other numerous
warnings in connection with i915. The result this produced was:

> git bisect good
ba01cc9346bce45a8861f36bce2c4c5d44b800b2 is the first bad commit
commit ba01cc9346bce45a8861f36bce2c4c5d44b800b2
Author: John Harrison <John.C.Harrison at Intel.com>
Date:   Fri May 29 17:43:41 2015 +0100

    drm/i915: Update i915_switch_context() to take a request structure

    Now that the request is guaranteed to specify the context, it is possible
to
    update the context switch code to use requests rather than ring and context
    pairs. This patch updates i915_switch_context() accordingly.

    Also removed the warning that the request's context must match the last
context
    switch's context. As the context switch now gets the context object from
the
    request structure, there is no longer any scope for the two to become out
of
    step.

    For: VIZ-5115
    Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
    Reviewed-by: Tomas Elf <tomas.elf at intel.com>
    Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

:040000 040000 3717675a773aafd62ff883278f0a9dd0b4747af9
0f32cac1cb40d7d1f757495a85e77bf39863862a M     drivers
---

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