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Date: Fri, 25 Apr 2014 09:54:33 -0400 (EDT) From: Alan Stern <stern@...land.harvard.edu> To: Li Zhong <zhong@...ux.vnet.ibm.com> cc: Tejun Heo <tj@...nel.org>, Johan Hovold <jhovold@...il.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>, <rafael.j.wysocki@...el.com> Subject: Re: [PATCH] USB: serial: fix sysfs-attribute removal deadlock 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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