From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Pierre Ossman <drzeus-mmc@drzeus.cx>,
Zdenek Kabelac <zdenek.kabelac@gmail.com>,
Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: [Bug 10030] Suspend doesn't work when SD card is inserted
Date: Thu, 21 Feb 2008 17:38:40 +0100 [thread overview]
Message-ID: <200802211738.41552.rjw@sisk.pl> (raw)
In-Reply-To: <Pine.LNX.4.44L0.0802211115380.4528-100000@iolanthe.rowland.org>
On Thursday, 21 of February 2008, Alan Stern wrote:
> On Thu, 21 Feb 2008, Rafael J. Wysocki wrote:
>
> > > > +bool in_suspend_context(void)
> > > > +{
> > > > + bool result;
> > > > +
> > > > + mutex_lock(&suspending_task_mtx);
> > > > + result = (suspending_task == current);
> > > > + mutex_unlock(&suspending_task_mtx);
> > > > + return result;
> > > > +}
> > >
> > > If suspending_task == current then you are guaranteed to be serialized,
> > > because everything a single task does is serial.
> >
> > As I said before (but that doesn't seem to reach the list, so I'm repeating),
> > this is to protect other tasks from reading an inconsistent value of
> > suspending_task in case they attempt to remove a device concurrently with
> > respect to us.
> >
> > While this is not likely to happen right now, because of the freezer, it may
> > very well happen when the freezer is finally removed.
>
> Sorry, I don't understand. Are you worried that process A might set
> suspending_task = A but then process B might still see suspending_task
> == NULL? Or that A might set suspend_task = NULL but then B might
> still see suspending_task == A?
>
> Neither one will cause any problem, since the only case that matters is
> when B sees suspending_task == B -- and that can happen if and only if
> B was the last process to set suspending_task.
>
> In fact, you might as well get rid of the set_suspending_task() routine
> entirely and just put the assignments inline.
OK, I will.
> > --- linux-2.6.orig/drivers/base/core.c
> > +++ linux-2.6/drivers/base/core.c
> > @@ -929,6 +929,11 @@ void device_del(struct device *dev)
> > struct device *parent = dev->parent;
> > struct class_interface *class_intf;
> >
> > + if (in_suspend_context()) {
> > + get_device(dev);
>
> Where is this get_device() undone? Shouldn't there be an extra
> put_device() added to unregister_dropped_devices()?
No, I don't think so, because unregister_dropped_devices() calls
device_unregister() that does the put_device() eventually.
If we are called by device_unregister(), the get_device() is needed to balance
the put_device() that will be called by device_unregister() after we return.
OTOH, if we are called directly, then we need to balance the put_device()
that will be done by device_unregister() called from
unregister_dropped_devices().
I hope I didn't miss anything.
> > + device_pm_schedule_removal(dev);
> > + return;
> > + }
> > device_pm_remove(dev);
> > if (parent)
> > klist_del(&dev->knode_parent);
>
> And now the change to device_destroy() isn't needed at all.
No, it's not. Didn't I remove it? I thought I did.
Thanks,
Rafael
next prev parent reply other threads:[~2008-02-21 16:40 UTC|newest]
Thread overview: 92+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20080219232338.E9A24108068@picon.linux-foundation.org>
2008-02-20 16:42 ` [Bug 10030] Suspend doesn't work when SD card is inserted Alan Stern
2008-02-20 17:30 ` Pierre Ossman
2008-02-20 19:26 ` Alan Stern
2008-02-20 20:51 ` Pierre Ossman
2008-02-20 20:58 ` Rafael J. Wysocki
2008-02-20 21:06 ` Alan Stern
2008-02-20 22:15 ` Rafael J. Wysocki
2008-02-20 22:24 ` Alan Stern
2008-02-20 22:41 ` Rafael J. Wysocki
2008-02-21 0:02 ` Rafael J. Wysocki
2008-02-21 16:27 ` Alan Stern
2008-02-21 16:38 ` Rafael J. Wysocki [this message]
2008-02-21 17:48 ` Alan Stern
2008-02-21 22:47 ` Rafael J. Wysocki
2008-02-21 23:05 ` Alan Stern
2008-02-23 1:30 ` Rafael J. Wysocki
2008-02-23 4:39 ` Alan Stern
2008-02-23 20:16 ` Rafael J. Wysocki
2008-02-23 23:29 ` Alan Stern
2008-02-24 0:19 ` Rafael J. Wysocki
2008-02-24 3:25 ` Alan Stern
2008-02-24 4:26 ` [linux-pm] " Alan Stern
2008-02-24 14:00 ` Rafael J. Wysocki
2008-02-24 15:33 ` Bugs in MMC [was: [Bug 10030] Suspend doesn't work when SD card is inserted] Alan Stern
2008-02-25 17:41 ` Pierre Ossman
2008-02-25 17:58 ` Alan Stern
2008-02-25 18:31 ` Pierre Ossman
2008-02-25 20:00 ` Alan Stern
2008-03-01 14:11 ` Pierre Ossman
2008-03-01 14:36 ` Alan Stern
2008-03-01 14:47 ` Pierre Ossman
2008-02-25 22:51 ` Felipe Balbi
2008-03-03 21:59 ` David Brownell
2008-03-04 6:03 ` Pierre Ossman
2008-03-04 9:44 ` David Brownell
2008-03-04 9:58 ` Pierre Ossman
2008-03-06 21:23 ` David Brownell
2008-03-04 17:53 ` Alan Stern
2008-03-04 18:53 ` David Brownell
2008-03-04 19:51 ` Alan Stern
2008-03-04 20:30 ` David Brownell
2008-03-04 21:00 ` Alan Stern
2008-03-06 15:55 ` Pavel Machek
2008-03-06 20:33 ` Alan Stern
2008-03-06 20:53 ` Zdenek Kabelac
2008-03-06 21:31 ` Rafael J. Wysocki
2008-03-04 17:50 ` Alan Stern
2008-02-24 13:33 ` [Bug 10030] Suspend doesn't work when SD card is inserted Rafael J. Wysocki
2008-02-24 20:25 ` Rafael J. Wysocki
2008-02-24 20:45 ` Alan Stern
2008-02-24 20:56 ` Rafael J. Wysocki
2008-02-24 21:11 ` Alan Stern
2008-02-24 22:18 ` Rafael J. Wysocki
2008-02-24 13:51 ` Rafael J. Wysocki
2008-02-24 19:27 ` Alan Stern
2008-02-24 19:42 ` Zdenek Kabelac
2008-02-24 20:09 ` Rafael J. Wysocki
2008-02-24 18:21 ` Pavel Machek
2008-02-24 19:03 ` Alan Stern
2008-02-24 20:11 ` Pavel Machek
2008-02-24 20:33 ` Alan Stern
2008-02-24 21:42 ` Pavel Machek
2008-02-24 22:21 ` Rafael J. Wysocki
2008-02-25 2:21 ` Alan Stern
2008-02-25 11:41 ` Rafael J. Wysocki
[not found] ` <c4e36d110802250402q7312a488idf752e07db7504e8@mail.gmail.com>
2008-02-25 12:31 ` Rafael J. Wysocki
2008-02-25 2:19 ` Alan Stern
2008-02-25 9:03 ` using long instead of atomic_t when only set/read is required (was Re: [Bug 10030] Suspend doesn't work when SD card is inserted) Pavel Machek
2008-02-25 14:46 ` Alan Stern
2008-03-03 12:08 ` [patch] Re: using long instead of atomic_t when only set/read is required Pavel Machek
2008-03-03 15:42 ` Alan Stern
2008-03-03 15:53 ` Alan Cox
2008-03-03 17:11 ` Alan Stern
2008-03-03 17:26 ` Linus Torvalds
2008-03-03 17:44 ` Pavel Machek
2008-03-03 19:27 ` Alan Stern
2008-03-06 15:58 ` Mark Lord
2008-03-06 16:11 ` Linus Torvalds
2008-03-06 16:27 ` Mark Lord
2008-03-03 17:16 ` Nick Piggin
2008-03-03 17:31 ` Paul E. McKenney
2008-03-03 17:33 ` Alan Cox
2008-03-03 17:22 ` Paul E. McKenney
2008-03-03 15:48 ` Alan Cox
2008-03-03 17:24 ` Pavel Machek
2008-03-03 20:27 ` Rafael J. Wysocki
2008-03-03 21:12 ` Paul E. McKenney
2008-03-03 22:23 ` Linus Torvalds
2008-03-04 23:32 ` Peter Hartley
2008-03-04 23:54 ` Rafael J. Wysocki
2008-03-05 0:26 ` Paul E. McKenney
2008-02-25 11:40 ` [Bug 10030] Suspend doesn't work when SD card is inserted Rafael J. Wysocki
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