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author | Chris Wilson <chris@chris-wilson.co.uk> | 2019-02-08 15:37:03 +0000 |
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committer | Chris Wilson <chris@chris-wilson.co.uk> | 2019-02-08 16:47:32 +0000 |
commit | 2caffbf1176256cc4f8d4e5c3c524fc689cb9876 (patch) | |
tree | 03bb0b9e29b61ae6886c84308cea1a446eb469eb /drivers/gpu/drm/i915/i915_gem_fence_reg.c | |
parent | 7ae1940014ef77e6389ca95a5a75273c9c4ea31f (diff) | |
download | linux-stable-2caffbf1176256cc4f8d4e5c3c524fc689cb9876.tar.gz linux-stable-2caffbf1176256cc4f8d4e5c3c524fc689cb9876.tar.bz2 linux-stable-2caffbf1176256cc4f8d4e5c3c524fc689cb9876.zip |
drm/i915: Revoke mmaps and prevent access to fence registers across reset
Previously, we were able to rely on the recursive properties of
struct_mutex to allow us to serialise revoking mmaps and reacquiring the
FENCE registers with them being clobbered over a global device reset.
I then proceeded to throw out the baby with the bath water in order to
pursue a struct_mutex-less reset.
Perusing LWN for alternative strategies, the dilemma on how to serialise
access to a global resource on one side was answered by
https://lwn.net/Articles/202847/ -- Sleepable RCU:
1 int readside(void) {
2 int idx;
3 rcu_read_lock();
4 if (nomoresrcu) {
5 rcu_read_unlock();
6 return -EINVAL;
7 }
8 idx = srcu_read_lock(&ss);
9 rcu_read_unlock();
10 /* SRCU read-side critical section. */
11 srcu_read_unlock(&ss, idx);
12 return 0;
13 }
14
15 void cleanup(void)
16 {
17 nomoresrcu = 1;
18 synchronize_rcu();
19 synchronize_srcu(&ss);
20 cleanup_srcu_struct(&ss);
21 }
No more worrying about stop_machine, just an uber-complex mutex,
optimised for reads, with the overhead pushed to the rare reset path.
However, we do run the risk of a deadlock as we allocate underneath the
SRCU read lock, and the allocation may require a GPU reset, causing a
dependency cycle via the in-flight requests. We resolve that by declaring
the driver wedged and cancelling all in-flight rendering.
v2: Use expedited rcu barriers to match our earlier timing
characteristics.
v3: Try to annotate locking contexts for sparse
v4: Reduce selftest lock duration to avoid a reset deadlock with fences
v5: s/srcu/reset_backoff_srcu/
v6: Remove more stale comments
Testcase: igt/gem_mmap_gtt/hang
Fixes: eb8d0f5af4ec ("drm/i915: Remove GPU reset dependence on struct_mutex")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190208153708.20023-2-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/gpu/drm/i915/i915_gem_fence_reg.c')
-rw-r--r-- | drivers/gpu/drm/i915/i915_gem_fence_reg.c | 36 |
1 files changed, 9 insertions, 27 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem_fence_reg.c b/drivers/gpu/drm/i915/i915_gem_fence_reg.c index be89bd95ab7c..1ec1417cf8b4 100644 --- a/drivers/gpu/drm/i915/i915_gem_fence_reg.c +++ b/drivers/gpu/drm/i915/i915_gem_fence_reg.c @@ -270,6 +270,10 @@ static int fence_update(struct drm_i915_fence_reg *fence, return 0; } + ret = i915_reset_trylock(fence->i915); + if (ret < 0) + goto out_rpm; + fence_write(fence, vma); fence->vma = vma; @@ -278,8 +282,12 @@ static int fence_update(struct drm_i915_fence_reg *fence, list_move_tail(&fence->link, &fence->i915->mm.fence_list); } + i915_reset_unlock(fence->i915, ret); + ret = 0; + +out_rpm: intel_runtime_pm_put(fence->i915, wakeref); - return 0; + return ret; } /** @@ -443,32 +451,6 @@ void i915_unreserve_fence(struct drm_i915_fence_reg *fence) } /** - * i915_gem_revoke_fences - revoke fence state - * @dev_priv: i915 device private - * - * Removes all GTT mmappings via the fence registers. This forces any user - * of the fence to reacquire that fence before continuing with their access. - * One use is during GPU reset where the fence register is lost and we need to - * revoke concurrent userspace access via GTT mmaps until the hardware has been - * reset and the fence registers have been restored. - */ -void i915_gem_revoke_fences(struct drm_i915_private *dev_priv) -{ - int i; - - lockdep_assert_held(&dev_priv->drm.struct_mutex); - - for (i = 0; i < dev_priv->num_fence_regs; i++) { - struct drm_i915_fence_reg *fence = &dev_priv->fence_regs[i]; - - GEM_BUG_ON(fence->vma && fence->vma->fence != fence); - - if (fence->vma) - i915_vma_revoke_mmap(fence->vma); - } -} - -/** * i915_gem_restore_fences - restore fence state * @dev_priv: i915 device private * |