Date: Tue, 26 Apr 2011 08:27:14 -0600 From: Warner Losh <imp@bsdimp.com> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-hackers@freebsd.org, Bartosz Fabianowski <freebsd@chillt.de> Subject: Re: Is there some implicit locking of device methods? Message-ID: <5627117D-499B-4FD7-BF84-BE4BE6F583D7@bsdimp.com> In-Reply-To: <201104260942.03543.jhb@freebsd.org> References: <4DB695DB.1080505@chillt.de> <201104260942.03543.jhb@freebsd.org>
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On Apr 26, 2011, at 7:42 AM, John Baldwin wrote: > - The Giant protection for new-bus should prevent attach/detach from = running > concurrently I believe (either that or the USB bus itself should = ensure > that the two instances of your device have seperate device_t = instances with > separate softc's, so current attach/detach should not matter except = that > they may both try to talk to the same hardware perhaps? In that = case that > is something the USB bus driver should fix by prevent a device from > attaching at an existing address until any existing device at that = address > is fully detached). I thought that if we held Giant when we're about to go to sleep that we = drop it as a special case. So if any newbus-releated function sleeps, = we can have a situation where attach is running and detach gets called. = There is (or was) some code to cope with this in CardBus, iirc. I'm = surprised there isn't any in USB, since Hans was the one that alerted me = to this issue. Warner
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