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From: Herbert Xu <herbert@gondor.apana.org.au>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Jason@zx2c4.com, linux-kernel@vger.kernel.org, tytso@mit.edu,
	tglx@linutronix.de, peterz@infradead.org
Subject: Re: [PATCH 5/5] random: Defer processing of randomness on PREEMPT_RT.
Date: Mon, 20 Dec 2021 13:56:56 +1100	[thread overview]
Message-ID: <20211220025656.GB20311@gondor.apana.org.au> (raw)
In-Reply-To: <Yb7/3JUcDENyYySN@linutronix.de>

On Sun, Dec 19, 2021 at 10:48:12AM +0100, Sebastian Andrzej Siewior wrote:
>
> That one. I find the semantic difficult to understand. Some BH-user
> check sock_owned_by_user(), some don't.
> However, a semaphore should work. The atomic user would do
> down_trylock() while preemptible caller would invoke down() and sleep
> until the lock is available. Let me check if that works here…

Right, if your atomic user can simply discard the work then this
is enough.

In the network case, we can't just discard the packet so that's
why there is a backlog queue which the atomic user appends to
if the lock isn't available.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

  reply	other threads:[~2021-12-20  2:57 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-07 12:17 [PATCH 0/5] random: Add PREEMPT_RT support Sebastian Andrzej Siewior
2021-12-07 12:17 ` [PATCH 1/5] random: Remove unused irq_flags argument from add_interrupt_randomness() Sebastian Andrzej Siewior
2021-12-07 12:44   ` Wei Liu
2021-12-07 17:35   ` Jason A. Donenfeld
2021-12-07 12:17 ` [PATCH 2/5] irq: Remove unsued flags argument from __handle_irq_event_percpu() Sebastian Andrzej Siewior
2021-12-07 17:41   ` Jason A. Donenfeld
2021-12-11 22:39     ` Thomas Gleixner
2021-12-12 21:13       ` Jason A. Donenfeld
2021-12-07 12:17 ` [PATCH 3/5] random: Split add_interrupt_randomness() Sebastian Andrzej Siewior
2021-12-07 12:17 ` [PATCH 4/5] random: Move the fast_pool reset into the caller Sebastian Andrzej Siewior
2021-12-07 12:17 ` [PATCH 5/5] random: Defer processing of randomness on PREEMPT_RT Sebastian Andrzej Siewior
2021-12-07 18:14   ` Jason A. Donenfeld
2021-12-07 20:10     ` Sebastian Andrzej Siewior
2021-12-13 15:16       ` Sebastian Andrzej Siewior
2021-12-17  2:23       ` Herbert Xu
2021-12-17  9:00         ` Sebastian Andrzej Siewior
2021-12-18  3:24           ` Herbert Xu
2021-12-19  9:48             ` Sebastian Andrzej Siewior
2021-12-20  2:56               ` Herbert Xu [this message]
2021-12-20 14:38       ` Jason A. Donenfeld
2022-01-12 17:49         ` Sebastian Andrzej Siewior
2022-01-30 22:55           ` Jason A. Donenfeld
2022-01-31 16:33             ` Sebastian Andrzej Siewior
2022-02-04 15:31               ` [PATCH RFC v1] random: do not take spinlocks in irq handler Jason A. Donenfeld
2022-02-04 15:58                 ` Jason A. Donenfeld
2022-02-04 20:53                   ` Sebastian Andrzej Siewior
2022-02-04 20:47                 ` Sebastian Andrzej Siewior
2022-02-04 22:08                   ` Jason A. Donenfeld
2022-02-04 23:09                     ` [PATCH v2] random: defer fast pool mixing to worker Jason A. Donenfeld
2022-02-05  4:02                   ` [PATCH RFC v1] random: do not take spinlocks in irq handler Sultan Alsawaf
2022-02-05 12:50                     ` Jason A. Donenfeld

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