From: Keshavamurthy Anil S <anil.s.keshavamurthy@intel.com>
To: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: Keshavamurthy Anil S <anil.s.keshavamurthy@intel.com>,
Greg KH <greg@kroah.com>,
Hotplug List <linux-hotplug-devel@lists.sourceforge.net>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] kobject: fix double kobject_put in kobject_unregister()
Date: Wed, 10 Nov 2004 22:39:18 +0000 [thread overview]
Message-ID: <20041110143918.B13668@unix-os.sc.intel.com> (raw)
In-Reply-To: <20041110223016.C26346@flint.arm.linux.org.uk>; from rmk+lkml@arm.linux.org.uk on Wed, Nov 10, 2004 at 10:30:16PM +0000
On Wed, Nov 10, 2004 at 10:30:16PM +0000, Russell King wrote:
> On Wed, Nov 10, 2004 at 02:19:23PM -0800, Keshavamurthy Anil S wrote:
> > Hi Greg,
> >
> > This patch fixes the problem where in kobject resources were getting
> > freed when those kobject were still in use due to double kobject_put()
> > getting called in the kobject_unregister() code path.
>
> Isn't it intended that, after an sysfs/kobject/device object is
> unregistered that the thread doing the unregistering must not
> dereference the memory associated with that object?
Yes, nobody is touching the resource once it is freed. But because of
double kobject_put() getting called in the kobject_unregister() code patch
I am seeing successive parent's kobject_unregister() causing panic as that kobject's
kobject_cleanup() gets called when childs kobject_unregiser() is getting called.
i.e patern's kobject_cleanup() gets called for some reason when clild's kobject_unregister()
is called. My patch fixes this issues.
>
> IOW, the sequence:
>
> allocate
> register (refcount >= 2 after this completes)
> unregister
>
> will automatically free the object once the last user has gone.
>
> --
> Russell King
> Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
> maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/
> 2.6 Serial core
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WARNING: multiple messages have this Message-ID (diff)
From: Keshavamurthy Anil S <anil.s.keshavamurthy@intel.com>
To: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: Keshavamurthy Anil S <anil.s.keshavamurthy@intel.com>,
Greg KH <greg@kroah.com>,
Hotplug List <linux-hotplug-devel@lists.sourceforge.net>,
Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] kobject: fix double kobject_put in kobject_unregister()
Date: Wed, 10 Nov 2004 14:39:18 -0800 [thread overview]
Message-ID: <20041110143918.B13668@unix-os.sc.intel.com> (raw)
In-Reply-To: <20041110223016.C26346@flint.arm.linux.org.uk>; from rmk+lkml@arm.linux.org.uk on Wed, Nov 10, 2004 at 10:30:16PM +0000
On Wed, Nov 10, 2004 at 10:30:16PM +0000, Russell King wrote:
> On Wed, Nov 10, 2004 at 02:19:23PM -0800, Keshavamurthy Anil S wrote:
> > Hi Greg,
> >
> > This patch fixes the problem where in kobject resources were getting
> > freed when those kobject were still in use due to double kobject_put()
> > getting called in the kobject_unregister() code path.
>
> Isn't it intended that, after an sysfs/kobject/device object is
> unregistered that the thread doing the unregistering must not
> dereference the memory associated with that object?
Yes, nobody is touching the resource once it is freed. But because of
double kobject_put() getting called in the kobject_unregister() code patch
I am seeing successive parent's kobject_unregister() causing panic as that kobject's
kobject_cleanup() gets called when childs kobject_unregiser() is getting called.
i.e patern's kobject_cleanup() gets called for some reason when clild's kobject_unregister()
is called. My patch fixes this issues.
>
> IOW, the sequence:
>
> allocate
> register (refcount >= 2 after this completes)
> unregister
>
> will automatically free the object once the last user has gone.
>
> --
> Russell King
> Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
> maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/
> 2.6 Serial core
next prev parent reply other threads:[~2004-11-10 22:39 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-11-10 22:19 [PATCH] kobject: fix double kobject_put in kobject_unregister() Keshavamurthy Anil S
2004-11-10 22:19 ` Keshavamurthy Anil S
2004-11-10 22:30 ` Russell King
2004-11-10 22:30 ` Russell King
2004-11-10 22:39 ` Keshavamurthy Anil S [this message]
2004-11-10 22:39 ` Keshavamurthy Anil S
2004-11-10 22:54 ` Greg KH
2004-11-10 22:54 ` Greg KH
2004-11-10 23:04 ` Keshavamurthy Anil S
2004-11-10 23:04 ` Keshavamurthy Anil S
2004-11-11 2:03 ` Keiichiro Tokunaga
2004-11-11 2:03 ` Keiichiro Tokunaga
2004-11-11 1:54 ` Keshavamurthy Anil S
2004-11-11 1:54 ` Keshavamurthy Anil S
2004-11-11 1:54 ` Keshavamurthy Anil S
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