On Tue, Aug 27, 2013 at 08:34:05PM +0200, Lars-Peter Clausen wrote: > The pl330 DMA driver is broken in regard to handling a terminate all request > while it is processing the list of completed descriptors. This is most visible > when calling dmaengine_terminate_all() from within the descriptors callback > for > cyclic transfers. In this case the TERMINATE_ALL transfer will clear the > work_list and stop the transfer. But after all callbacks for all completed > descriptors have been handled the descriptors will be re-enqueued into the > (now > empty) work_list. So the next time dma_async_issue_pending() is called for the > channel these descriptors will be transferred again which will cause data > corruption. Similar issues can occur if dmaengine_terminate_all() is not > called > from within the descriptor callback but runs on a different CPU at the same > time > as the completed descriptor list is processed. > > This patch introduces a new per channel list which will hold the completed > descriptors. While processing the list the channel's lock will be held to > avoid > racing against dmaengine_terminate_all(). The lock will be released when > calling > the descriptors callback though. Since the list of completed descriptors might > be modified (e.g. by calling dmaengine_terminate_all() from the callback) we > can > not use the normal list iterator macros. Instead we'll need to check for each > loop iteration again if there are still items in the list. The drivers > TERMINATE_ALL implementation is updated to move descriptors from both the > work_list as well the new completed_list back to the descriptor pool. This > makes > sure that none of the descripts finds its way back into the work list and also > that we do not call any futher complete callbacks after > dmaengine_terminate_all() has been called.
Applied, thanks ~Vinod -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
