From: Thomas Gleixner <tglx@linutronix.de>
To: Herbert Xu <herbert@gondor.apana.org.au>,
Ard Biesheuvel <ardb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>
Subject: Re: [PATCH] crypto: lib/chacha20poly1305 - Set SG_MITER_ATOMIC unconditionally
Date: Tue, 15 Sep 2020 21:04:01 +0200 [thread overview]
Message-ID: <874kny6evy.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20200915101043.GA27327@gondor.apana.org.au>
On Tue, Sep 15 2020 at 20:10, Herbert Xu wrote:
> On Tue, Sep 15, 2020 at 01:08:31PM +0300, Ard Biesheuvel wrote:
>>
>> But making atomic kmap preemptible/sleepable creates the exact same
>> problem, i.e., that we have no idea which existing callers are
>> currently relying on those preemption disabling semantics, so we can't
>> just take them away. Or am I missing something?
>
> Good point.
>
> Thomas mentioned that RT has been doing this for a while now so
> perhaps someone has studied this problem already? Thomas?
RT is substituting preempt_disable() with migrate_disable() which pins
the task on the CPU so that per CPU stuff still works. And we did quite
some staring whether there is code which purely relies on the
preempt_disable() to prevent reentrancy, but there is almost none.
Though we don't have migrate disable on !RT and PeterZ is not a great
fan of making it available as it wreckages schedulability - though IMO
not much more than preempt disable :)
Thanks,
tglx
next prev parent reply other threads:[~2020-09-15 19:05 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200914204209.256266093@linutronix.de>
[not found] ` <20200914204441.579902354@linutronix.de>
2020-09-15 16:10 ` [patch 06/13] locking/bitspinlock: Clenaup PREEMPT_COUNT leftovers Will Deacon
[not found] ` <20200914204441.375753691@linutronix.de>
2020-09-15 16:11 ` [patch 04/13] lockdep: " Will Deacon
[not found] ` <CAHk-=win80rdof8Pb=5k6gT9j_v+hz-TQzKPVastZDvBe9RimQ@mail.gmail.com>
2020-09-15 17:25 ` [patch 00/13] preempt: Make preempt count unconditional Paul E. McKenney
[not found] ` <871rj4owfn.fsf@nanos.tec.linutronix.de>
[not found] ` <CAHk-=wj0eUuVQ=hRFZv_nY7g5ZLt7Fy3K7SMJL0ZCzniPtsbbg@mail.gmail.com>
[not found] ` <CAHk-=wjOV6f_ddg+QVCF6RUe+pXPhSR2WevnNyOs9oT+q2ihEA@mail.gmail.com>
2020-09-15 3:30 ` [PATCH] crypto: lib/chacha20poly1305 - Set SG_MITER_ATOMIC unconditionally Herbert Xu
2020-09-15 6:03 ` Ard Biesheuvel
2020-09-15 6:40 ` Herbert Xu
2020-09-15 6:45 ` Linus Torvalds
2020-09-15 6:55 ` Linus Torvalds
2020-09-15 7:05 ` Herbert Xu
2020-09-15 7:10 ` Ard Biesheuvel
2020-09-15 9:34 ` Thomas Gleixner
2020-09-15 10:02 ` Ard Biesheuvel
2020-09-15 10:05 ` Herbert Xu
2020-09-15 10:08 ` Ard Biesheuvel
2020-09-15 10:10 ` Herbert Xu
2020-09-15 19:04 ` Thomas Gleixner [this message]
2020-09-15 7:08 ` Ard Biesheuvel
2020-09-15 6:20 ` [patch 00/13] preempt: Make preempt count unconditional Ard Biesheuvel
[not found] ` <20200915062253.GA26275@gondor.apana.org.au>
2020-09-15 6:39 ` Linus Torvalds
2020-09-15 7:24 ` Thomas Gleixner
2020-09-15 17:29 ` Linus Torvalds
2020-09-15 8:39 ` Thomas Gleixner
2020-09-15 17:35 ` Linus Torvalds
2020-09-15 19:57 ` Thomas Gleixner
2020-09-16 18:34 ` Linus Torvalds
2020-09-16 7:37 ` Daniel Vetter
2020-09-16 15:29 ` Paul E. McKenney
2020-09-16 18:32 ` Linus Torvalds
2020-09-16 20:43 ` Paul E. McKenney
2020-09-17 6:38 ` Ard Biesheuvel
2020-09-16 20:29 ` Daniel Vetter
2020-09-16 20:58 ` Paul E. McKenney
2020-09-16 21:43 ` Daniel Vetter
2020-09-16 22:39 ` Paul E. McKenney
2020-09-17 7:52 ` Daniel Vetter
2020-09-17 16:28 ` Paul E. McKenney
2020-09-29 8:19 ` Michal Hocko
2020-09-29 8:19 ` Michal Hocko
2020-09-29 8:20 ` Michal Hocko
2020-09-29 8:21 ` Michal Hocko
2020-09-29 8:23 ` Michal Hocko
2020-09-29 9:00 ` Daniel Vetter
2020-09-29 14:54 ` Michal Hocko
2020-09-16 19:23 ` Matthew Wilcox
2020-09-16 20:48 ` Paul E. McKenney
[not found] ` <20200914204441.268144917@linutronix.de>
2020-09-16 10:56 ` [patch 03/13] preempt: Clenaup PREEMPT_COUNT leftovers Valentin Schneider
[not found] ` <20200914204441.794954043@linutronix.de>
2020-09-16 10:56 ` [patch 08/13] sched: " Valentin Schneider
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