bus: mhi: host: Drop chan lock before queuing buffers

Ensure read and write locks for the channel are not taken in succession by
dropping the read lock from parse_xfer_event() such that a callback given
to client can potentially queue buffers and acquire the write lock in that
process. Any queueing of buffers should be done without channel read lock
acquired as it can result in multiple locks and a soft lockup.

Cc: <[email protected]> # 5.7
Fixes: 1d3173a3bae7 ("bus: mhi: core: Add support for processing events from client device")
Signed-off-by: Qiang Yu <[email protected]>
Reviewed-by: Jeffrey Hugo <[email protected]>
Tested-by: Jeffrey Hugo <[email protected]>
Reviewed-by: Manivannan Sadhasivam <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[mani: added fixes tag and cc'ed stable]
Signed-off-by: Manivannan Sadhasivam <[email protected]>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index ad7807e4b523..abb561db9ae1 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -644,6 +644,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
 			mhi_del_ring_element(mhi_cntrl, tre_ring);
 			local_rp = tre_ring->rp;
 
+			read_unlock_bh(&mhi_chan->lock);
+
 			/* notify client */
 			mhi_chan->xfer_cb(mhi_chan->mhi_dev, &result);
 
@@ -669,6 +671,8 @@ static int parse_xfer_event(struct mhi_controller *mhi_cntrl,
 					kfree(buf_info->cb_buf);
 				}
 			}
+
+			read_lock_bh(&mhi_chan->lock);
 		}
 		break;
 	} /* CC_EOT */