Re: [PATCH v9 3/5] crypto: drbg - add async seeding operation
Am Donnerstag, 21. Mai 2015, 05:44:08 schrieb Herbert Xu:
Hi Herbert,
> On Wed, May 20, 2015 at 10:03:45PM +0200, Stephan Mueller wrote:
> >> @@ -1487,6 +1514,7 @@ unlock:
> > */
> >
> > static int drbg_uninstantiate(struct drbg_state *drbg)
> > {
> >
> > + cancel_work_sync(&drbg->seed_work);
>
> This will just block until the work is done, i.e., until the
> pool is ready. It's no different to an uninterruptible sleep.
>
> So either just do an uninterruptible sleep, or allow the async
> seed to fail.
I think I found the issue: we cannot put interruptible and noninterruptible
sleeps onto the same wait queue. With my initial tests, I put the
uninterruptible sleep onto urandom_init_wait where also interruptible sleeps
are put onto.
So, I will create a 2nd wait queue in random.c for uninterruptible waits,
change the get_blocking_random_bytes back to void and use wait_event to wait
for the initialization.
>
> Cheers,
--
Ciao
Stephan
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Re: [PATCH v9 3/5] crypto: drbg - add async seeding operation
On Thu, May 21, 2015 at 08:53:13AM +0200, Stephan Mueller wrote: > > Thank you for pointing that out - I have seen that too. But the crux is that > when using wait_event, the cancel function to serialize the destruction code > path will *not* return at all, even when the async callback function > completed > successfully. Hence the choice for wait_event_interruptible Why is that? It should return when the pool is initialised and your work completes. If it does not then that means either the pool isn't initialising or somehow your code is racy and getting stuck. If it's racy then wait_event_interruptible is just hiding the real problem. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v9 3/5] crypto: drbg - add async seeding operation
Am Donnerstag, 21. Mai 2015, 14:36:18 schrieb Herbert Xu: Hi Herbert, >On Thu, May 21, 2015 at 08:10:13AM +0200, Stephan Mueller wrote: >> The cancel operation is needed as otherwise my drbg context handle will be >> removed by the crypto API during the sleep. That is the whole reason why >> wait_event_interruptible is used. >> >> So, even when using an uninterruptible sleep, the crypto API has no >> knowledge about it and I have to serialize the destruction code path with >> the async callback. > >I understand. But if you use the uniterruptible version at least >you won't have to deal with bogus early returns. Thank you for pointing that out - I have seen that too. But the crux is that when using wait_event, the cancel function to serialize the destruction code path will *not* return at all, even when the async callback function completed successfully. Hence the choice for wait_event_interruptible > >The cancel by itself will *not* cause wait_event_interruptible >to return early. Somebody has to send it a signal for that to >happen. Correct. But I can only wake it up with a handle on urandom_init_wait on which the wait sleeps. That handle lives in random.c. So, to wake it up, I need another piece of code in random.c. That piece of code used to be the get_blocking_random_bytes_cancel function I offered in previous patches. As Ted mentioned, he did not want to much code in random.c for this. In addition, if I understand you correctly in previous emails, it would be acceptable to wait until the callback was triggered (and thus causing the caller module to be not unloadable for that period of time. Ciao Stephan -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v9 3/5] crypto: drbg - add async seeding operation
On Thu, May 21, 2015 at 08:10:13AM +0200, Stephan Mueller wrote: > > The cancel operation is needed as otherwise my drbg context handle will be > removed by the crypto API during the sleep. That is the whole reason why > wait_event_interruptible is used. > > So, even when using an uninterruptible sleep, the crypto API has no knowledge > about it and I have to serialize the destruction code path with the async > callback. I understand. But if you use the uniterruptible version at least you won't have to deal with bogus early returns. The cancel by itself will *not* cause wait_event_interruptible to return early. Somebody has to send it a signal for that to happen. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v9 3/5] crypto: drbg - add async seeding operation
Am Donnerstag, 21. Mai 2015, 05:44:08 schrieb Herbert Xu:
Hi Herbert,
> On Wed, May 20, 2015 at 10:03:45PM +0200, Stephan Mueller wrote:
> >> @@ -1487,6 +1514,7 @@ unlock:
> > */
> >
> > static int drbg_uninstantiate(struct drbg_state *drbg)
> > {
> >
> > + cancel_work_sync(&drbg->seed_work);
>
> This will just block until the work is done, i.e., until the
> pool is ready. It's no different to an uninterruptible sleep.
>
> So either just do an uninterruptible sleep, or allow the async
> seed to fail.
>
The cancel operation is needed as otherwise my drbg context handle will be
removed by the crypto API during the sleep. That is the whole reason why
wait_event_interruptible is used.
So, even when using an uninterruptible sleep, the crypto API has no knowledge
about it and I have to serialize the destruction code path with the async
callback.
--
Ciao
Stephan
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Re: [PATCH v9 3/5] crypto: drbg - add async seeding operation
On Wed, May 20, 2015 at 10:03:45PM +0200, Stephan Mueller wrote:
>> @@ -1487,6 +1514,7 @@ unlock:
> */
> static int drbg_uninstantiate(struct drbg_state *drbg)
> {
> + cancel_work_sync(&drbg->seed_work);
This will just block until the work is done, i.e., until the
pool is ready. It's no different to an uninterruptible sleep.
So either just do an uninterruptible sleep, or allow the async
seed to fail.
Cheers,
--
Email: Herbert Xu
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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