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authorDani Liberman <dliberman@habana.ai>2021-11-17 10:59:10 +0300
committerOded Gabbay <ogabbay@kernel.org>2021-12-26 09:59:07 +0300
commit3beaf903a3a07dc5c6500691b0b465d36292e3f8 (patch)
tree91c6da3ed6c9347ee96947f7337ac709956f6ed2 /drivers/misc
parentcad9eb4a8d9f745c2548f905534f981758e2afec (diff)
downloadlinux-3beaf903a3a07dc5c6500691b0b465d36292e3f8.tar.xz
habanalabs: fix race condition in multi CS completion
Race example scenario: 1. User have 2 threads that waits on multi CS: - thread_0 waits on QID 0 and uses multi CS context 0. - thread_1 waits on QID 1 and uses multi CS context 1. 2. thread_1 got completion and release multi CS context 1. 3. CS related to multi CS of thread_0 starts executing complete_multi_cs function, the first iteration of the loop completes the multi CS of thread_0, hence multi CS context 0 is released. 4. thread_1 waits on QID 1 and uses multi CS context 0. 5. thread_0 waits on QID 0 and uses multi CS context 1. 6. The second iterattion of the loop (from step 3) starts, which means, start checking multi CS context 1: - multi CS contetxt is being used by thread_0 waiting on QID 0. - The fence of the CS (still CS from step 3) has QID map the same as the multi CS context 1. - multi CS context 1 (thread_0) gets completion on CS that triggered already thread_0 (with multi CS context 0) and is no longer being waited on. Fixed by exiting the loop in complete_multi_cs after getting completion Signed-off-by: Dani Liberman <dliberman@habana.ai> Reviewed-by: Oded Gabbay <ogabbay@kernel.org> Signed-off-by: Oded Gabbay <ogabbay@kernel.org>
Diffstat (limited to 'drivers/misc')
-rw-r--r--drivers/misc/habanalabs/common/command_submission.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/drivers/misc/habanalabs/common/command_submission.c b/drivers/misc/habanalabs/common/command_submission.c
index c1fd4ba14c60..4e893364a3cc 100644
--- a/drivers/misc/habanalabs/common/command_submission.c
+++ b/drivers/misc/habanalabs/common/command_submission.c
@@ -545,6 +545,13 @@ static void complete_multi_cs(struct hl_device *hdev, struct hl_cs *cs)
* mcs fences.
*/
fence->mcs_handling_done = true;
+ /*
+ * Since CS (and its related fence) can be associated with only one
+ * multi CS context, once it triggered multi CS completion no need to
+ * continue checking other multi CS contexts.
+ */
+ spin_unlock(&mcs_compl->lock);
+ break;
}
spin_unlock(&mcs_compl->lock);