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authorChris Wilson <chris@chris-wilson.co.uk>2017-11-14 16:27:19 +0000
committerSumit Semwal <sumit.semwal@linaro.org>2017-11-21 22:37:05 +0530
commit03e4e0a9e02cf703da331ff6cfd57d0be9bf5692 (patch)
treedc27892dd1af53bf9d6f5f1925762e7b8286f992 /include/linux/dma-fence-array.h
parent70c5f93669249886b151812076509f30569aff80 (diff)
dma-buf/fence: Fix lock inversion within dma-fence-array
Ages ago Rob Clark noted, "Currently with fence-array, we have a potential deadlock situation. If we fence_add_callback() on an array-fence, the array-fence's lock is acquired first, and in it's ->enable_signaling() callback, it will install cbs on it's array-member fences, so the array-member's lock is acquired second. But in the signal path, the array-member's lock is acquired first, and the array-fence's lock acquired second." Rob proposed either extensive changes to dma-fence to unnest the fence-array signaling, or to defer the signaling onto a workqueue. This is a more refined version of the later, that should keep the latency of the fence signaling to a minimum by using an irq-work, which is executed asap. Reported-by: Rob Clark <robdclark@gmail.com> Suggested-by: Rob Clark <robdclark@gmail.com> References: 1476635975-21981-1-git-send-email-robdclark@gmail.com Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Cc: Rob Clark <robdclark@gmail.com> Cc: Gustavo Padovan <gustavo.padovan@collabora.co.uk> Cc: Sumit Semwal <sumit.semwal@linaro.org> Cc: Christian König <christian.koenig@amd.com> Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org> Link: https://patchwork.freedesktop.org/patch/msgid/20171114162719.30958-1-chris@chris-wilson.co.uk
Diffstat (limited to 'include/linux/dma-fence-array.h')
-rw-r--r--include/linux/dma-fence-array.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/dma-fence-array.h b/include/linux/dma-fence-array.h
index 332a5420243c..bc8940ca280d 100644
--- a/include/linux/dma-fence-array.h
+++ b/include/linux/dma-fence-array.h
@@ -21,6 +21,7 @@
#define __LINUX_DMA_FENCE_ARRAY_H
#include <linux/dma-fence.h>
+#include <linux/irq_work.h>
/**
* struct dma_fence_array_cb - callback helper for fence array
@@ -47,6 +48,8 @@ struct dma_fence_array {
unsigned num_fences;
atomic_t num_pending;
struct dma_fence **fences;
+
+ struct irq_work work;
};
extern const struct dma_fence_ops dma_fence_array_ops;