From: "Paul E. McKenney" <paulmck@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Daniel Vetter <daniel@ffwll.ch>,
Thomas Gleixner <tglx@linutronix.de>,
Ard Biesheuvel <ardb@kernel.org>,
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"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@vger.kernel.org>
Subject: Re: [patch 00/13] preempt: Make preempt count unconditional
Date: Wed, 16 Sep 2020 13:43:59 -0700 [thread overview]
Message-ID: <20200916204359.GB29330@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <CAHk-=wjsMycgMHJrCmeetR3r+K5bpSRtmVWfd8iaoQCYd_VYAg@mail.gmail.com>
On Wed, Sep 16, 2020 at 11:32:00AM -0700, Linus Torvalds wrote:
> On Wed, Sep 16, 2020 at 8:29 AM Paul E. McKenney <paulmck@kernel.org> wrote:
> >
> > All fair, but some of us need to write code that must handle being
> > invoked from a wide variety of contexts.
>
> Note that I think that core functionality is different from random drivers.
>
> Of course core code can (and will) look at things like
>
> if (in_interrupt())
> .. schedule work asynchronously ..
>
> because core code ends up being called from odd places, and code like
> that is expected to have understanding of the rules it plays with.
>
> But something like RCU is a very different beast from some "walk the
> scatter-gather list" code.
>
> RCU does its work in the background, and works with lots of different
> things. And it's so core and used everywhere that it knows about these
> things. I mean, we literally have special code explicitly to let RCU
> know "we entered kernel context now".
>
> But something like a driver list walking thing should not be doing
> different things behind peoples back depending on whether they hold
> spinlocks or not. It should either just work regardless, or there
> should be a flag (or special interface) for the "you're being called
> in a crtitical region".
>
> Because dynamically changing behavior really is very confusing.
Whew! I feel much better now. ;-)
Thanx, Paul
next prev parent reply other threads:[~2020-09-16 20:44 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
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 [this message]
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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