From 03e4e0a9e02cf703da331ff6cfd57d0be9bf5692 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Tue, 14 Nov 2017 16:27:19 +0000 Subject: dma-buf/fence: Fix lock inversion within dma-fence-array MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Suggested-by: Rob Clark References: 1476635975-21981-1-git-send-email-robdclark@gmail.com Signed-off-by: Chris Wilson Cc: Rob Clark Cc: Gustavo Padovan Cc: Sumit Semwal Cc: Christian König Reviewed-by: Christian König Signed-off-by: Sumit Semwal Link: https://patchwork.freedesktop.org/patch/msgid/20171114162719.30958-1-chris@chris-wilson.co.uk --- drivers/base/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/base') diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index 1a5f6a157a57..62b0de06836e 100644 --- a/drivers/base/Kconfig +++ b/drivers/base/Kconfig @@ -244,6 +244,7 @@ config DMA_SHARED_BUFFER bool default n select ANON_INODES + select IRQ_WORK help This option enables the framework for buffer-sharing between multiple drivers. A buffer is associated with a file using driver -- cgit v1.2.3