On 1/27/21 8:16 PM, Can Guo wrote:
ufshcd_compl_tm() looks for all 0 bits in the REG_UTP_TASK_REQ_DOOR_BELL
and call complete() for each req who has the req->end_io_data set. There
can be a race condition btw tmc send/compl, because the req->end_io_data is
set, in __ufshcd_issue_tm_cmd(), without host lock protection, so it is
possible that when ufshcd_compl_tm() checks the req->end_io_data, it is set
but the corresponding tag has not been set in REG_UTP_TASK_REQ_DOOR_BELL.
Thus, ufshcd_tmc_handler() may wrongly complete TMRs which have not been
sent out. Fix it by protecting req->end_io_data with host lock, and let
ufshcd_compl_tm() only handle those tm cmds which have been completed
instead of looking for 0 bits in the REG_UTP_TASK_REQ_DOOR_BELL.
I don't know any other block driver that needs locking to protect races
between submission and completion context. Can the block layer timeout
mechanism be used instead of the mechanism introduced by this patch,
e.g. by using blk_execute_rq_nowait() to submit requests? That would
allow to reuse the existing mechanism in the block layer core to handle
races between request completion and timeout handling.
Thanks,
Bart.