Hi,
On Thu, Oct 17, 2019 at 3:26 PM Tero Kristo <t-kristo@xxxxxx> wrote:
>
> Currently crypto_wait_req waits indefinitely for an async crypto request
> to complete. This is bad as it can cause for example the crypto test
> manager to hang without any notification as to why it has happened.
> Instead of waiting indefinitely, add a 1 second timeout to the call,
> and provide a warning print if a timeout happens.
While the incentive is clear and positive, this suggested solution
creates problems of its own.
In many (most?) cases where we are waiting here, we are waiting for a
DMA operation to finish from hardware.
Exiting while this pending DMA operation is not finished, even with a
proper error return value, is dangerous because
unless the calling code takes great care to not release the memory the
DMA is being done from/to, this can have disastrous effects.
As Eric has already mentioned, one second might seem like a long time,
but we don't really know if it is enough.
How about adding a second API (ig. crypto_wait_req_timeout) which
supports a calee specified timeout where
the calle knows how to correctly deal with timeout and port the
relevant call sites to use this?
Thanks!
Gilad
>
> Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
> ---
> include/linux/crypto.h | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/crypto.h b/include/linux/crypto.h
> index 19ea3a371d7b..b8f0e5c3cc0c 100644
> --- a/include/linux/crypto.h
> +++ b/include/linux/crypto.h
> @@ -682,8 +682,15 @@ static inline int crypto_wait_req(int err, struct crypto_wait *wait)
> switch (err) {
> case -EINPROGRESS:
> case -EBUSY:
> - wait_for_completion(&wait->completion);
> + err = wait_for_completion_timeout(&wait->completion,
> + msecs_to_jiffies(1000));
> reinit_completion(&wait->completion);
> + if (!err) {
> + pr_err("%s: timeout for %p\n", __func__, wait);
> + err = -ETIMEDOUT;
> + break;
> + }
> +
> err = wait->err;
> break;
> };
> --
> 2.17.1
>
> --
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
--
Gilad Ben-Yossef
Chief Coffee Drinker
values of β will give rise to dom!
