From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Jarek Poplawski <jarkao2@o2.pl>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH] lockdep: fix ide/proc interaction
Date: Thu, 19 Oct 2006 13:05:56 +0200 [thread overview]
Message-ID: <1161255956.3036.84.camel@taijtu> (raw)
In-Reply-To: <20061019084051.GB1872@ff.dom.local>
On Thu, 2006-10-19 at 10:40 +0200, Jarek Poplawski wrote:
> On 18-10-2006 20:49, Peter Zijlstra wrote:
> > Index: linux-2.6/drivers/ide/ide.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/ide/ide.c
> > +++ linux-2.6/drivers/ide/ide.c
> > @@ -973,8 +973,8 @@ ide_settings_t *ide_find_setting_by_name
> > * @drive: drive
> > *
> > * Automatically remove all the driver specific settings for this
> > - * drive. This function may sleep and must not be called from IRQ
> > - * context. The caller must hold ide_setting_sem.
> > + * drive. This function may not be called from IRQ context. The
> > + * caller must hold ide_setting_sem.
> > */
> >
> > static void auto_remove_settings (ide_drive_t *drive)
> > @@ -1874,11 +1874,22 @@ void ide_unregister_subdriver(ide_drive_
> > {
> > unsigned long flags;
> >
> > - down(&ide_setting_sem);
> > - spin_lock_irqsave(&ide_lock, flags);
> > #ifdef CONFIG_PROC_FS
> > ide_remove_proc_entries(drive->proc, driver->proc);
>
> But now:
> > (proc_subdir_lock){--..}, at: [<c04a33b0>] remove_proc_entry+0x40/0x191
>
> is taken here with irqs and bhs enabled (btw. this: {--..} looks
> as if it wasn't called from here with spin_lock_irqsave?)
> IMHO it is hard to believe this lock isn't anywhere used in
> hard or soft irq context so probably local_irq_disable/enable
> or local_bh_disable/enable is needed around this.
it really isnt, check fs/proc/{generic,proc_devtree}.c
> > #endif
> > + down(&ide_setting_sem);
> > + spin_lock_irqsave(&ide_lock, flags);
> > + /*
> > + * ide_setting_sem protects the settings list
> > + * ide_lock protects the use of settings
> > + *
> > + * so we need to hold both, ide_settings_sem because we want to
> > + * modify the settings list, and ide_lock because we cannot take
> > + * a setting out that is being used.
> > + *
> > + * OTOH both ide_{read,write}_setting are only ever used under
> > + * ide_setting_sem.
> > + */
> > auto_remove_settings(drive);
>
> But why auto_remove_settings and __ide_remove_setting comments
> don't mention this ide_lock?
Because comments suck ;-) and it might not be needed, see the OTOH.
Feel free to send a patch updating the comments.
Peter
next prev parent reply other threads:[~2006-10-19 11:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-18 18:49 [PATCH] lockdep: fix ide/proc interaction Peter Zijlstra
2006-10-19 8:40 ` Jarek Poplawski
2006-10-19 11:05 ` Peter Zijlstra [this message]
2006-10-19 12:37 ` Jarek Poplawski
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