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From: Peter Zijlstra <peterz@infradead.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: "Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm@kvack.org, "Andrew Morton" <akpm@linux-foundation.org>,
	"David Rientjes" <rientjes@google.com>,
	"Christian König" <christian.koenig@amd.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>
Subject: Re: [PATCH 2/4] kernel.h: Add non_block_start/end()
Date: Mon, 10 Dec 2018 15:47:11 +0100	[thread overview]
Message-ID: <20181210144711.GN5289@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20181210141337.GQ1286@dhcp22.suse.cz>

On Mon, Dec 10, 2018 at 03:13:37PM +0100, Michal Hocko wrote:
> I do not see any scheduler guys Cced and it would be really great to get
> their opinion here.
> 
> On Mon 10-12-18 11:36:39, Daniel Vetter wrote:
> > In some special cases we must not block, but there's not a
> > spinlock, preempt-off, irqs-off or similar critical section already
> > that arms the might_sleep() debug checks. Add a non_block_start/end()
> > pair to annotate these.
> > 
> > This will be used in the oom paths of mmu-notifiers, where blocking is
> > not allowed to make sure there's forward progress.
> 
> Considering the only alternative would be to abuse
> preempt_{disable,enable}, and that really has a different semantic, I
> think this makes some sense. The cotext is preemptible but we do not
> want notifier to sleep on any locks, WQ etc.

I'm confused... what is this supposed to do?

And what does 'block' mean here? Without preempt_disable/IRQ-off we're
subject to regular preemption and execution can stall for arbitrary
amounts of time.

The Changelog doesn't yield any clues.

WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: "Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"Intel Graphics Development" <intel-gfx@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	linux-mm@kvack.org, "Jérôme Glisse" <jglisse@redhat.com>,
	"David Rientjes" <rientjes@google.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [PATCH 2/4] kernel.h: Add non_block_start/end()
Date: Mon, 10 Dec 2018 15:47:11 +0100	[thread overview]
Message-ID: <20181210144711.GN5289@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20181210141337.GQ1286@dhcp22.suse.cz>

On Mon, Dec 10, 2018 at 03:13:37PM +0100, Michal Hocko wrote:
> I do not see any scheduler guys Cced and it would be really great to get
> their opinion here.
> 
> On Mon 10-12-18 11:36:39, Daniel Vetter wrote:
> > In some special cases we must not block, but there's not a
> > spinlock, preempt-off, irqs-off or similar critical section already
> > that arms the might_sleep() debug checks. Add a non_block_start/end()
> > pair to annotate these.
> > 
> > This will be used in the oom paths of mmu-notifiers, where blocking is
> > not allowed to make sure there's forward progress.
> 
> Considering the only alternative would be to abuse
> preempt_{disable,enable}, and that really has a different semantic, I
> think this makes some sense. The cotext is preemptible but we do not
> want notifier to sleep on any locks, WQ etc.

I'm confused... what is this supposed to do?

And what does 'block' mean here? Without preempt_disable/IRQ-off we're
subject to regular preemption and execution can stall for arbitrary
amounts of time.

The Changelog doesn't yield any clues.
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

  reply	other threads:[~2018-12-10 14:47 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-10 10:36 [PATCH 0/4] mmu notifier debug checks v2 Daniel Vetter
2018-12-10 10:36 ` [PATCH 1/4] mm: Check if mmu notifier callbacks are allowed to fail Daniel Vetter
2018-12-10 10:36   ` Daniel Vetter
2018-12-10 10:44   ` Koenig, Christian
2018-12-10 10:44     ` Koenig, Christian
2018-12-10 13:27   ` Michal Hocko
2018-12-10 13:27     ` Michal Hocko
2018-12-10 10:36 ` [PATCH 2/4] kernel.h: Add non_block_start/end() Daniel Vetter
2018-12-10 10:36   ` Daniel Vetter
2018-12-10 14:13   ` Michal Hocko
2018-12-10 14:13     ` Michal Hocko
2018-12-10 14:47     ` Peter Zijlstra [this message]
2018-12-10 14:47       ` Peter Zijlstra
2018-12-10 15:01       ` Michal Hocko
2018-12-10 15:22         ` Peter Zijlstra
2018-12-10 16:20           ` Michal Hocko
2018-12-10 16:30             ` Peter Zijlstra
2018-12-10 16:30               ` Peter Zijlstra
2018-12-12 10:26               ` Daniel Vetter
2018-12-12 10:26                 ` Daniel Vetter
2018-12-10 10:36 ` [PATCH 3/4] mm, notifier: Catch sleeping/blocking for !blockable Daniel Vetter
2018-12-10 10:36 ` [PATCH 4/4] mm, notifier: Add a lockdep map for invalidate_range_start Daniel Vetter
2018-12-10 12:07 ` ✗ Fi.CI.CHECKPATCH: warning for mmu notifier debug checks v2 Patchwork
2018-12-10 12:28 ` ✓ Fi.CI.BAT: success " Patchwork
2018-12-10 15:54 ` ✗ Fi.CI.IGT: failure " Patchwork
2018-12-10 16:47 ` ✗ Fi.CI.BAT: failure for mmu notifier debug checks v2 (rev2) Patchwork
2019-05-20 21:39 [PATCH 1/4] mm: Check if mmu notifier callbacks are allowed to fail Daniel Vetter
2019-05-20 21:39 ` [PATCH 2/4] kernel.h: Add non_block_start/end() Daniel Vetter
2019-05-20 21:39   ` Daniel Vetter

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