Date: Wed, 31 Aug 2011 19:46:22 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Warner Losh <imp@bsdimp.com> Cc: Hans Petter Selasky <hselasky@FreeBSD.org>, John Baldwin <jhb@FreeBSD.org>, freebsd-arch@FreeBSD.org Subject: Re: skipping locks, mutex_owned, usb Message-ID: <4E5E655E.8060505@FreeBSD.org> In-Reply-To: <DD9206EC-A969-434A-ABC5-15B2857C571C@bsdimp.com> References: <4E53986B.5000804@FreeBSD.org> <4E5A099F.4060903@FreeBSD.org> <201108281127.44696.hselasky@freebsd.org> <201108310943.24476.jhb@freebsd.org> <4E5E5DA0.4060003@FreeBSD.org> <DD9206EC-A969-434A-ABC5-15B2857C571C@bsdimp.com>
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on 31/08/2011 19:32 Warner Losh said the following: > > On Aug 31, 2011, at 10:13 AM, Andriy Gapon wrote: >> So why the mutex unwinding/rewinding code is present at all? >> What kind of situations is it supposed to prevent? >> >> Personally I think that we either know that those drivers should not hold the >> locks in question (bus_mtx and xfer_mtx) or we know that they hold them. >> I do not see why we have to be conditional here or have a loop even... > > Today, I think we know these things. In the past, as the code was written, there was a lot more special case code needed for giant cohabitation. Since you chimed in... :-) I have a hard time imagining a situation where that code is useful today or was useful before. Any example, purely hypothetical even, would do. -- Andriy Gapon
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