[Bug 108456] userptr deadlock in Vulkan CTS: mmu_notifier vs workers vs struct_mutex

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108456

Chris Wilson <chris at chris-wilson.co.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #30 from Chris Wilson <chris at chris-wilson.co.uk> ---
commit 484d9a844d0d0aeaa4cd3cec20885b7de9986a55 (HEAD -> drm-intel-next-queued,
drm-intel/for-linux-next, drm-intel/drm-intel-next-queued)
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Tue Jan 15 12:44:42 2019 +0000

    drm/i915/userptr: Avoid struct_mutex recursion for
mmu_invalidate_range_start

    Since commit 93065ac753e4 ("mm, oom: distinguish blockable mode for mmu
    notifiers") we have been able to report failure from
    mmu_invalidate_range_start which allows us to use a trylock on the
    struct_mutex to avoid potential recursion and report -EBUSY instead.
    Furthermore, this allows us to pull the work into the main callback and
    avoid the sleight-of-hand in using a workqueue to avoid lockdep.

    However, not all paths to mmu_invalidate_range_start are prepared to
    handle failure, so instead of reporting the recursion, deal with it by
    propagating the failure upwards, who can decide themselves to handle it
    or report it.

    v2: Mark up the recursive lock behaviour and comment on the various weak
    points.

    v3: Follow commit 3824e41975ae ("drm/i915: Use mutex_lock_killable() from
    inside the shrinker") and also use mutex_lock_killable().
    v3.1: No leak on EINTR.

    Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108375
    References: 93065ac753e4 ("mm, oom: distinguish blockable mode for mmu
notifiers")
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
    Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
    Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
    Link:
https://patchwork.freedesktop.org/patch/msgid/20190115124442.3500-1-chris@chris-wilson.co.uk

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