Date: Tue, 31 May 2005 20:19:08 +0000 From: Alexander Kabaev <kan@freebsd.org> To: Maksim Yevmenkin <maksim.yevmenkin@savvis.net> Cc: Norbert Koch <NKoch@demig.de>, freebsd-hackers@freebsd.org Subject: Re: mutual exclusion in vkbd Message-ID: <20050531201908.GA77068@freefall.freebsd.org> In-Reply-To: <429C93AE.8060509@savvis.net> References: <000001c565f6$d46b7720$4801a8c0@ws-ew-3.W2KDEMIG> <429C93AE.8060509@savvis.net>
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On Tue, May 31, 2005 at 09:41:18AM -0700, Maksim Yevmenkin wrote: > Norbert, > > >I am currently trying to backport vkbd to FreeBSD 4. > > ok > > >Maksim Yevmenkin uses mtx_lock()/mtx_unlock() for > >protecting access to data structures under FreeBSD 5/6 > >between the device functions and the kernel thread. > > > >How should I best do this under FreeBSD 4? > > > >Would something like splhigh() work in that context? > >Or should I use lockmgr with LK_EXCLUSIVE/LK_RELEASE? > >Is there any (pseudo)process context inside a kernel task? > > spltty() is what you probably need to use. you could just adjust the > following defines like > > #define VKBD_LOCK_DECL int > #define VKBD_LOCK_INIT(s) /* noop */ > #define VKBD_LOCK_DESTROY(s) /* noop */ > #define VKBD_LOCK(s) (s)->ks_lock = spltty() > #define VKBD_UNLOCK(s) splx((s)->ks_lock) > #define VKBD_LOCK_ASSERT(s, w) > #define VKBD_SLEEP(s, f, d, t) \ > tsleep(&(s)->f, PCATCH | (PZERO + 1), d, t) > The code above will probably crash the kernel in many spectacular and unpredictable ways. You will need to save interrupt flags locally to each VKBD_LOCK caller or they will end up restoring each other's flags. -- Alexander Kabaev
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