summaryrefslogtreecommitdiffstats
path: root/Documentation/gpu/i915.rst
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/gpu/i915.rst')
-rw-r--r--Documentation/gpu/i915.rst46
1 files changed, 46 insertions, 0 deletions
diff --git a/Documentation/gpu/i915.rst b/Documentation/gpu/i915.rst
index 429b08aac797..33cc6ddf8f64 100644
--- a/Documentation/gpu/i915.rst
+++ b/Documentation/gpu/i915.rst
@@ -329,6 +329,52 @@ for execution also include a list of all locations within buffers that
refer to GPU-addresses so that the kernel can edit the buffer correctly.
This process is dubbed relocation.
+Locking Guidelines
+------------------
+
+.. note::
+ This is a description of how the locking should be after
+ refactoring is done. Does not necessarily reflect what the locking
+ looks like while WIP.
+
+#. All locking rules and interface contracts with cross-driver interfaces
+ (dma-buf, dma_fence) need to be followed.
+
+#. No struct_mutex anywhere in the code
+
+#. dma_resv will be the outermost lock (when needed) and ww_acquire_ctx
+ is to be hoisted at highest level and passed down within i915_gem_ctx
+ in the call chain
+
+#. While holding lru/memory manager (buddy, drm_mm, whatever) locks
+ system memory allocations are not allowed
+
+ * Enforce this by priming lockdep (with fs_reclaim). If we
+ allocate memory while holding these looks we get a rehash
+ of the shrinker vs. struct_mutex saga, and that would be
+ real bad.
+
+#. Do not nest different lru/memory manager locks within each other.
+ Take them in turn to update memory allocations, relying on the object’s
+ dma_resv ww_mutex to serialize against other operations.
+
+#. The suggestion for lru/memory managers locks is that they are small
+ enough to be spinlocks.
+
+#. All features need to come with exhaustive kernel selftests and/or
+ IGT tests when appropriate
+
+#. All LMEM uAPI paths need to be fully restartable (_interruptible()
+ for all locks/waits/sleeps)
+
+ * Error handling validation through signal injection.
+ Still the best strategy we have for validating GEM uAPI
+ corner cases.
+ Must be excessively used in the IGT, and we need to check
+ that we really have full path coverage of all error cases.
+
+ * -EDEADLK handling with ww_mutex
+
GEM BO Management Implementation Details
----------------------------------------