Messages in this thread | | | Date | Thu, 11 Aug 2022 02:17:31 +0200 | From | "Jason A. Donenfeld" <> | Subject | Re: [PATCH] random: use raw spinlocks for use on RT |
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Hey Sebastian,
On Mon, Aug 01, 2022 at 04:34:13PM +0200, Sebastian Andrzej Siewior wrote: > On 2022-08-01 16:25:31 [+0200], Jason A. Donenfeld wrote: > > After handling several bug reports using various creative solutions, > > it's becoming clear that random bytes are actually a useful thing to > > happen from any ordinary context, including when interruptsare off. > > Actually, that's been long recognized, which is why the RNG uses > > spinlocks rather than mutexes. But on RT, those spinlocks are getting > > converted back into sleeping locks. > > > > This clearly is causing more problems than it might hypothetically > > solve. Additionally, the locks in random.c are generally for fixed > > durations doing CPU-bound operations -- no waiting for hardware or I/O > > or the like. So this shouldn't result in a real harm to latency. > > > > Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> > > --- > > Sebastian - I won't move forward with this without your Ack, obviously. > > What do you think of this general approach? -Jason > > I would need to do worst-case measurements and I've been looking at this > just before writting the other email and there was a local_lock_t > somewhere which needs also change…
Did you ever come up some measurements here? It sure would be nice if I could apply this, but obviously that's contingent on you saying it's okay latency-wise on RT.
Jason
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