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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/selftests/intel_hangcheck.c | |
parent | 7ae1940014ef77e6389ca95a5a75273c9c4ea31f (diff) | |
download | linux-2caffbf1176256cc4f8d4e5c3c524fc689cb9876.tar.bz2 |
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/selftests/intel_hangcheck.c')
-rw-r--r-- | drivers/gpu/drm/i915/selftests/intel_hangcheck.c | 5 |
1 files changed, 2 insertions, 3 deletions
diff --git a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c index 7b6f3bea9ef8..4886fac12628 100644 --- a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c +++ b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c @@ -1039,8 +1039,6 @@ static int __igt_reset_evict_vma(struct drm_i915_private *i915, /* Check that we can recover an unbind stuck on a hanging request */ - igt_global_reset_lock(i915); - mutex_lock(&i915->drm.struct_mutex); err = hang_init(&h, i915); if (err) @@ -1138,7 +1136,9 @@ static int __igt_reset_evict_vma(struct drm_i915_private *i915, } out_reset: + igt_global_reset_lock(i915); fake_hangcheck(rq->i915, intel_engine_flag(rq->engine)); + igt_global_reset_unlock(i915); if (tsk) { struct igt_wedge_me w; @@ -1159,7 +1159,6 @@ fini: hang_fini(&h); unlock: mutex_unlock(&i915->drm.struct_mutex); - igt_global_reset_unlock(i915); if (i915_terminally_wedged(&i915->gpu_error)) return -EIO; |