[Intel-gfx] [PATCH] drm/i915/gem: Mark up the racy read of the mmap_singleton

[Intel-gfx] [PATCH] drm/i915/gem: Mark up the racy read of the mmap_singleton

[Chris Wilson]

[11057.642683] BUG: KCSAN: data-race in i915_gem_mmap [i915] / singleton_release [i915]
[11057.642717]
[11057.642740] write (marked) to 0xffff8881f24471a0 of 8 bytes by task 44668 on cpu 2:
[11057.643162]  singleton_release+0x38/0x60 [i915]
[11057.643192]  __fput+0x160/0x3c0
[11057.643217]  ____fput+0x16/0x20
[11057.643241]  task_work_run+0xba/0x100
[11057.643263]  exit_to_usermode_loop+0xe4/0xf0
[11057.643286]  do_syscall_64+0x27e/0x2c0
[11057.643314]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[11057.643339]
[11057.643359] read to 0xffff8881f24471a0 of 8 bytes by task 44667 on cpu 3:
[11057.643774]  i915_gem_mmap+0x295/0x670 [i915]
[11057.643802]  mmap_region+0x62b/0xac0
[11057.643825]  do_mmap+0x414/0x6b0
[11057.643848]  vm_mmap_pgoff+0xa9/0xf0
[11057.643875]  ksys_mmap_pgoff+0x1ac/0x2f0
[11057.643900]  do_syscall_64+0x6e/0x2c0
[11057.643924]  entry_SYSCALL_64_after_hwframe+0x44/0xa9

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gem/i915_gem_mman.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
index e8cccc131c40..b39c24dae64e 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
@@ -775,7 +775,7 @@ static struct file *mmap_singleton(struct drm_i915_private *i915)
 	struct file *file;
 
 	rcu_read_lock();
-	file = i915->gem.mmap_singleton;
+	file = READ_ONCE(i915->gem.mmap_singleton);
 	if (file && !get_file_rcu(file))
 		file = NULL;
 	rcu_read_unlock();
-- 
2.20.1

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[Intel-gfx] ✗ Fi.CI.BAT: failure for drm/i915/gem: Mark up the racy read of the mmap_singleton

[Patchwork]

== Series Details ==

Series: drm/i915/gem: Mark up the racy read of the mmap_singleton
URL   : https://patchwork.freedesktop.org/series/74531/
State : failure

== Summary ==

CI Bug Log - changes from CI_DRM_8112 -> Patchwork_16914
====================================================

Summary
-------

  **FAILURE**

  Serious unknown changes coming with Patchwork_16914 absolutely need to be
  verified manually.
  
  If you think the reported changes have nothing to do with the changes
  introduced in Patchwork_16914, please notify your bug team to allow them
  to document this new failure mode, which will reduce false positives in CI.

  External URL: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_16914/index.html

Possible new issues
-------------------

  Here are the unknown changes that may have been introduced in Patchwork_16914:

### IGT changes ###

#### Possible regressions ####

  * igt@i915_selftest@live@hangcheck:
    - fi-apl-guc:         [PASS][1] -> [DMESG-WARN][2]
   [1]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_8112/fi-apl-guc/igt@i915_selftest@live@hangcheck.html
   [2]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_16914/fi-apl-guc/igt@i915_selftest@live@hangcheck.html

  
Known issues
------------

  Here are the changes found in Patchwork_16914 that come from known issues:

### IGT changes ###

#### Issues hit ####

  * igt@i915_selftest@live@execlists:
    - fi-apl-guc:         [PASS][3] -> [INCOMPLETE][4] ([fdo#103927])
   [3]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_8112/fi-apl-guc/igt@i915_selftest@live@execlists.html
   [4]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_16914/fi-apl-guc/igt@i915_selftest@live@execlists.html

  * igt@i915_selftest@live@gem_contexts:
    - fi-cml-s:           [PASS][5] -> [DMESG-FAIL][6] ([i915#877])
   [5]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_8112/fi-cml-s/igt@i915_selftest@live@gem_contexts.html
   [6]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_16914/fi-cml-s/igt@i915_selftest@live@gem_contexts.html

  * igt@kms_addfb_basic@basic:
    - fi-tgl-y:           [PASS][7] -> [DMESG-WARN][8] ([CI#94] / [i915#402])
   [7]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_8112/fi-tgl-y/igt@kms_addfb_basic@basic.html
   [8]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_16914/fi-tgl-y/igt@kms_addfb_basic@basic.html

  
#### Possible fixes ####

  * igt@gem_exec_suspend@basic-s4-devices:
    - fi-tgl-y:           [FAIL][9] ([CI#94]) -> [PASS][10]
   [9]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_8112/fi-tgl-y/igt@gem_exec_suspend@basic-s4-devices.html
   [10]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_16914/fi-tgl-y/igt@gem_exec_suspend@basic-s4-devices.html

  * igt@kms_addfb_basic@unused-modifier:
    - fi-tgl-y:           [DMESG-WARN][11] ([CI#94] / [i915#402]) -> [PASS][12] +1 similar issue
   [11]: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_8112/fi-tgl-y/igt@kms_addfb_basic@unused-modifier.html
   [12]: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_16914/fi-tgl-y/igt@kms_addfb_basic@unused-modifier.html

  
  {name}: This element is suppressed. This means it is ignored when computing
          the status of the difference (SUCCESS, WARNING, or FAILURE).

  [CI#94]: https://gitlab.freedesktop.org/gfx-ci/i915-infra/issues/94
  [fdo#103927]: https://bugs.freedesktop.org/show_bug.cgi?id=103927
  [i915#402]: https://gitlab.freedesktop.org/drm/intel/issues/402
  [i915#877]: https://gitlab.freedesktop.org/drm/intel/issues/877
  [i915#998]: https://gitlab.freedesktop.org/drm/intel/issues/998


Participating hosts (44 -> 37)
------------------------------

  Additional (4): fi-skl-6770hq fi-bsw-nick fi-skl-6600u fi-bsw-n3050 
  Missing    (11): fi-bdw-5557u fi-hsw-4200u fi-byt-j1900 fi-hsw-peppy fi-glk-dsi fi-byt-squawks fi-kbl-7500u fi-ivb-3770 fi-byt-clapper fi-bdw-samus fi-kbl-r 


Build changes
-------------

  * CI: CI-20190529 -> None
  * Linux: CI_DRM_8112 -> Patchwork_16914

  CI-20190529: 20190529
  CI_DRM_8112: 032f2fe5c92eb1db6d417738431153c001a41bcc @ git://anongit.freedesktop.org/gfx-ci/linux
  IGT_5504: d6788bf0404f76b66170e18eb26c85004b5ccb25 @ git://anongit.freedesktop.org/xorg/app/intel-gpu-tools
  Patchwork_16914: 004a605cc4117b06a6e22ebb1ab733aed5a6f48d @ git://anongit.freedesktop.org/gfx-ci/linux


== Linux commits ==

004a605cc411 drm/i915/gem: Mark up the racy read of the mmap_singleton

== Logs ==

For more details see: https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_16914/index.html
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