From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Herbert Xu <herbert@gondor.apana.org.au>
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: Fri, 17 Dec 2021 10:00:52 +0100 [thread overview]
Message-ID: <YbxRxPdBDMu8KIy6@linutronix.de> (raw)
In-Reply-To: <20211217022338.GA19411@gondor.apana.org.au>
On 2021-12-17 13:23:38 [+1100], Herbert Xu wrote:
> Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> >
> > Even the IOCTL path must spin with disabled interrupts to avoid dead
> > locks. Therefore it makes no sense if attempt acquire the lock from
> > process or IRQ context. Something like
> > while (!raw_spin_trylock_irqsave())
> > cpu_relax()
>
> What about the TCP socket locking model?
>
> IOW, the user-space slow path will add itself to a backlog queue
> during contention, and the interrupt fast path will schedule work
> to process any user-space backlog on exit.
I'm sorry, I can't connect the dots here. I was trying to explain that
for the lock in question it is not possible to spin-wait without
disabling interrupts first.
> Cheers,
Sebastian
next prev parent reply other threads:[~2021-12-17 9:00 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 [this message]
2021-12-18 3:24 ` Herbert Xu
2021-12-19 9:48 ` Sebastian Andrzej Siewior
2021-12-20 2:56 ` Herbert Xu
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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