Date: Tue, 20 Dec 2011 17:42:23 +0100 From: Hans Petter Selasky <hselasky@c2i.net> To: Andriy Gapon <avg@freebsd.org> Cc: freebsd-usb@freebsd.org Subject: Re: ukbd locking update Message-ID: <201112201742.23998.hselasky@c2i.net> In-Reply-To: <4EF088C8.8090906@FreeBSD.org> References: <4EF088C8.8090906@FreeBSD.org>
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On Tuesday 20 December 2011 14:08:24 Andriy Gapon wrote: > I completing a patch that changes some locking in ukbd to account for > SCHEDULER_STOPPED and for other realities of the code. > > As a preview I would like to share couple of observations that had their > effect on the patch. > > 1. Acquiring Giant in device_attach, _detach in similar newbus method > implementations should be redundant because those are already executed with > Giant held. That's done either by the general newbus code or via > usbd_enum_lock() when the operations are executed in the USB explore > thread. > > 2. As discussed before: > if (!mutex_owned(&Giant)) > mutex_lock(&Giant) > this pattern does not make sense, because the Giant is recursive and can be > simply acquired without any check. > > Do you agree? Yes! --HPS
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