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From: Keith Busch <>
To: Lukas Wunner <>
Cc: "Hoyer, David" <>,
	"" <>
Subject: Re: Kernel hangs when powering up/down drive using sysfs
Date: Mon, 16 Mar 2020 11:42:00 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Mon, Mar 16, 2020 at 07:10:58PM +0100, Lukas Wunner wrote:
> On Mon, Mar 16, 2020 at 09:15:43AM -0700, Keith Busch wrote:
> > I'm not sure why the hard-irq context is even setting the thread running
> > flag while it can still exit without handling anything. Shouldn't it leave
> > the flag cleared until knows it's actually going to do something?
> No, ist_running must be set to true before the invocation of
> atomic_xchg(&ctrl->pending_events, 0).

Okay, I see what you mean.

Even with David's patch, there's still another condition that could exit
with ist_running set. It may make sense to move the setting just above
the atomic_xchg() so that clearing it doesn't need to be duplicated for
the remaining uncommon exit case.
> There's a time window between the atomic_xchg() and actually
> turning off the slot when pending_events is 0.  Previously we
> only checked in the sysfs functions that pending_events is 0.
> That was insufficient as we risked returning prematurely from
> the sysfs functions.  The point of ist_running is to prevent
> that.

Oh, right, I'm remembering now. And since we've a polled option for
pciehp, using synchronize_irq() from the sysfs path isn't possible.

  reply	other threads:[~2020-03-16 18:42 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-14 14:19 Kernel hangs when powering up/down drive using sysfs Hoyer, David
2020-03-16 16:15 ` Keith Busch
2020-03-16 18:10   ` Lukas Wunner
2020-03-16 18:42     ` Keith Busch [this message]
2020-03-18 11:53       ` Lukas Wunner
2020-03-16 18:19 ` Lukas Wunner
2020-03-16 18:25   ` Hoyer, David
2020-03-16 21:35     ` Hoyer, David
2020-03-18 11:49     ` Lukas Wunner
2020-03-18 14:06       ` Hoyer, David
2020-03-18 11:33 ` [PATCH] PCI: pciehp: Fix indefinite wait on sysfs requests Lukas Wunner
2020-03-18 16:43   ` Keith Busch
2020-03-28 20:25   ` Bjorn Helgaas

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