Hi Wolfram,
On 28.02.2024 11:03, Wolfram Sang wrote:
With the to-be-fixed commit, the reset_work handler cleared 'host->mrq'
outside of the spinlock protected critical section. That leaves a small
race window during execution of 'tmio_mmc_reset()' where the done_work
handler could grab a pointer to the now invalid 'host->mrq'. Both would
use it to call mmc_request_done() causing problems (see Link).
However, 'host->mrq' cannot simply be cleared earlier inside the
critical section. That would allow new mrqs to come in asynchronously
while the actual reset of the controller still needs to be done. So,
like 'tmio_mmc_set_ios()', an ERR_PTR is used to prevent new mrqs from
coming in but still avoiding concurrency between work handlers.
Reported-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/20240220061356.3001761-1-dirk.behme@xxxxxxxxxxxx/
Signed-off-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
Fixes: df3ef2d3c92c ("mmc: protect the tmio_mmc driver against a theoretical race")
Tested-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
Reviewed-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx>
---
Dirk: could you get this tested on your affected setups? I am somewhat
optimistic that this is already enough. For sure, it is a needed first
step.
Testing looks good :) Many thanks!
At least the issues we observed before are not seen any more. As we are
not exactly sure on the root cause, of course this is not a 100% proof.
But as the change looks good, looks like it won't break something and
the system behaves good with it I would say we are good to go.
I think we could add anything like
Cc: stable@xxxxxxxxxxxxxxx # 3.0+
?
drivers/mmc/host/tmio_mmc_core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/mmc/host/tmio_mmc_core.c b/drivers/mmc/host/tmio_mmc_core.c
index be7f18fd4836..c253d176db69 100644
--- a/drivers/mmc/host/tmio_mmc_core.c
+++ b/drivers/mmc/host/tmio_mmc_core.c
@@ -259,6 +259,8 @@ static void tmio_mmc_reset_work(struct work_struct *work)
else
mrq->cmd->error = -ETIMEDOUT;
+ /* No new calls yet, but disallow concurrent tmio_mmc_done_work() */
+ host->mrq = ERR_PTR(-EBUSY);
host->cmd = NULL;
host->data = NULL;
Thanks again!
Dirk
