Date: Tue, 26 Apr 2011 12:17:23 +0200 From: Hans Petter Selasky <hselasky@c2i.net> To: freebsd-hackers@freebsd.org Cc: Bartosz Fabianowski <freebsd@chillt.de> Subject: Re: Is there some implicit locking of device methods? Message-ID: <201104261217.23858.hselasky@c2i.net> In-Reply-To: <4DB695DB.1080505@chillt.de> References: <4DB695DB.1080505@chillt.de>
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On Tuesday 26 April 2011 11:52:27 Bartosz Fabianowski wrote: > 1. attach() is running and executes make_dev(). Before attach() has > finished, someone calls open() on the newly created device node and > tries to read from a device that is not fully instantiated. > > 2. read() is running when the device is suddenly pulled (this is a USB > device) so that detach() gets run. Thus, detach() starts tearing down > data structures that read() may still be accessing. Hi, You need to handle all cases in your driver. Fortunately there exists a solution for this already, called USB cdev. See serial/ulpt.c for example. --HPS
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