From: Alan Stern <stern@rowland.harvard.edu>
To: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>, Johan Hovold <jhovold@gmail.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
<linux-usb@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<rafael.j.wysocki@intel.com>
Subject: Re: [PATCH] USB: serial: fix sysfs-attribute removal deadlock
Date: Fri, 25 Apr 2014 09:54:33 -0400 (EDT) [thread overview]
Message-ID: <Pine.LNX.4.44L0.1404250953090.1140-100000@iolanthe.rowland.org> (raw)
In-Reply-To: <1398392134.2805.149.camel@ThinkPad-T5421.cn.ibm.com>
On Fri, 25 Apr 2014, Li Zhong wrote:
> > I don't get why try_module_get() matters here. We can't call into
> > ->store if the object at hand is already destroyed and the underlying
> > module can't go away if the target device is still alive.
> > try_module_get() doesn't actually protect the object. Why does that
> > matter? This is self removal, right? Can you please take a look at
> > kernfs_remove_self()?
>
> This is about one process writing something to driver attributes, and
> one process trying to unload this driver.
>
> I think try_module_get() could detect whether the driver is being
> unloaded, and if not, prevent it from being unloaded, so it could
> protect the object here by not allow the driver to be unloaded.
That isn't how try_module_get() works. If the module is being
unloaded, try_module_get() simply fails. It does not prevent the
module from being unloaded -- that's why its name begins with "try".
Alan Stern
next prev parent reply other threads:[~2014-04-25 13:54 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-23 9:32 [PATCH] USB: serial: fix sysfs-attribute removal deadlock Johan Hovold
2014-04-23 14:19 ` Tejun Heo
2014-04-24 8:29 ` Li Zhong
2014-04-24 14:35 ` Tejun Heo
2014-04-24 14:52 ` Johan Hovold
2014-04-25 2:16 ` Li Zhong
2014-04-25 10:15 ` Johan Hovold
2014-04-28 0:39 ` Li Zhong
2014-05-02 15:20 ` Tejun Heo
2014-04-25 13:59 ` Alan Stern
2014-04-28 1:58 ` Li Zhong
2014-04-25 2:15 ` Li Zhong
2014-04-25 13:54 ` Alan Stern [this message]
2014-04-25 15:13 ` Johan Hovold
2014-04-28 1:55 ` Li Zhong
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