Commit 2d319658 authored Oct 16, 2014 by Sahitya Tummala

mmc: core: Fix unclocked access in get_xfer_remain/stop_request

The unclocked access could happen in the following scenario -

1. mmcqd thread is waiting for previously submitted io to be done
2. before this io is done, it is woken up due to is_urgent event
3. mmcqd thread is running and is processing the is_urgent event
4. Just about the same time the previously submitted io is done and
it sets is_done_rcv flag, tries to wake up mmcqd thread and release
host clock so as to gate the clocks.

If step 3 and 4 happen at the same time, then clocks will be gated off
before is_urgent is completely handled. Hence, make sure to hold the
clock before invoking get_xfer_remain and stop_request host->op.

Change-Id: If03177bf5e28cc217cc8e86b10d81d4adbab78b9
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>

parent 3311f658

drivers/mmc/core/core.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -621,8 +621,10 @@ static bool mmc_should_stop_curr_req(struct mmc_host *host)
		(host->areq->cmd_flags & REQ_FUA))
		return false;

		mmc_host_clk_hold(host);
		remainder = (host->ops->get_xfer_remain) ?
		host->ops->get_xfer_remain(host) : -1;
		mmc_host_clk_release(host);
		return (remainder > 0);
		}

		@@ -647,6 +649,7 @@ static int mmc_stop_request(struct mmc_host *host)
		mmc_hostname(host));
		return -ENOTSUPP;
		}
		mmc_host_clk_hold(host);
		err = host->ops->stop_request(host);
		if (err) {
		pr_debug("%s: Call to host->ops->stop_request() failed (%d)\n",
		@@ -681,6 +684,7 @@ static int mmc_stop_request(struct mmc_host *host)
		goto out;
		}
		out:
		mmc_host_clk_release(host);
		return err;
		}