From: "Paul E. McKenney" <paulmck@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
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Subject: Re: [patch 00/13] preempt: Make preempt count unconditional
Date: Wed, 16 Sep 2020 13:48:41 -0700 [thread overview]
Message-ID: <20200916204841.GC29330@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200916192352.GO5449@casper.infradead.org>
On Wed, Sep 16, 2020 at 08:23:52PM +0100, Matthew Wilcox wrote:
> On Mon, Sep 14, 2020 at 11:55:24PM +0200, Thomas Gleixner wrote:
> > But just look at any check which uses preemptible(), especially those
> > which check !preemptible():
>
> hmm.
>
> +++ b/include/linux/preempt.h
> @@ -180,7 +180,9 @@ do { \
>
> #define preempt_enable_no_resched() sched_preempt_enable_no_resched()
>
> +#ifndef MODULE
> #define preemptible() (preempt_count() == 0 && !irqs_disabled())
> +#endif
>
> #ifdef CONFIG_PREEMPTION
> #define preempt_enable() \
>
>
> $ git grep -w preemptible drivers
> (slightly trimmed by hand to remove, eg, comments)
> drivers/firmware/arm_sdei.c: WARN_ON_ONCE(preemptible());
> drivers/firmware/arm_sdei.c: WARN_ON_ONCE(preemptible());
> drivers/firmware/arm_sdei.c: WARN_ON_ONCE(preemptible());
> drivers/firmware/arm_sdei.c: WARN_ON_ONCE(preemptible());
> drivers/firmware/arm_sdei.c: WARN_ON(preemptible());
> drivers/firmware/efi/efi-pstore.c: preemptible(), record->size, record->psi->buf);
> drivers/irqchip/irq-gic-v4.c: WARN_ON(preemptible());
> drivers/irqchip/irq-gic-v4.c: WARN_ON(preemptible());
> drivers/scsi/hisi_sas/hisi_sas_main.c: if (!preemptible())
> drivers/xen/time.c: BUG_ON(preemptible());
>
> That only looks like two drivers that need more than WARNectomies.
I could easily imagine someone thinking that these did something in
CONFIG_PREEMPT_NONE=y kernels. In fact, I could easily imagine myself
making that mistake. :-/
> Although maybe rcu_read_load_sched_held() or rcu_read_lock_any_held()
> might get called from a module ...
But yes, from the rcutorture module for certain and also from any other
RCU-using module that includes the usual RCU debug checks.
Thanx, Paul
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next prev parent reply other threads:[~2020-09-16 20:48 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-14 20:42 [patch 00/13] preempt: Make preempt count unconditional Thomas Gleixner
2020-09-14 20:42 ` [patch 01/13] lib/debug: Remove pointless ARCH_NO_PREEMPT dependencies Thomas Gleixner
2020-09-14 20:42 ` [patch 02/13] preempt: Make preempt count unconditional Thomas Gleixner
2020-09-14 20:42 ` [patch 03/13] preempt: Clenaup PREEMPT_COUNT leftovers Thomas Gleixner
2020-09-14 20:42 ` [patch 04/13] lockdep: " Thomas Gleixner
2020-09-15 16:11 ` Will Deacon
2020-09-14 20:42 ` [patch 05/13] mm/pagemap: " Thomas Gleixner
2020-09-14 20:42 ` [patch 06/13] locking/bitspinlock: " Thomas Gleixner
2020-09-15 16:10 ` Will Deacon
2020-09-14 20:42 ` [patch 07/13] uaccess: " Thomas Gleixner
2020-09-14 20:42 ` [patch 08/13] sched: " Thomas Gleixner
2020-09-14 20:42 ` [patch 09/13] ARM: " Thomas Gleixner
2020-09-14 20:42 ` [patch 10/13] xtensa: " Thomas Gleixner
2020-09-14 20:42 ` [patch 11/13] drm/i915: " Thomas Gleixner
2020-09-14 20:42 ` [patch 12/13] rcutorture: " Thomas Gleixner
2020-09-14 20:42 ` [patch 13/13] preempt: Remove PREEMPT_COUNT from Kconfig Thomas Gleixner
2020-09-14 20:54 ` [patch 00/13] preempt: Make preempt count unconditional Steven Rostedt
2020-09-14 20:59 ` Linus Torvalds
2020-09-14 21:55 ` Thomas Gleixner
2020-09-14 22:24 ` Linus Torvalds
2020-09-14 22:37 ` Linus Torvalds
2020-09-15 3:21 ` [PATCH] crypto: lib/chacha20poly1305 - Set SG_MITER_ATOMIC unconditionally Herbert Xu
2020-09-15 6:20 ` [patch 00/13] preempt: Make preempt count unconditional Ard Biesheuvel
2020-09-15 6:22 ` Herbert Xu
2020-09-15 6:39 ` Linus Torvalds
[not found] ` <87een35woz.fsf@nanos.tec.linutronix.de>
2020-09-15 17:29 ` Linus Torvalds
[not found] ` <87bli75t7v.fsf@nanos.tec.linutronix.de>
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 [this message]
2020-09-15 17:25 ` Paul E. McKenney
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