mutual exclusion in vkbd

[Norbert Koch]

Thank you all.
I'll try it.
Norbert

> -----Original Message-----
> From: owner-freebsd-hackers at freebsd.org
> [mailto:owner-freebsd-hackers at freebsd.org]On Behalf Of Maksim Yevmenkin
> Sent: Tuesday, May 31, 2005 10:59 PM
> To: Alexander Kabaev
> Cc: Norbert Koch; freebsd-hackers at freebsd.org
> Subject: Re: mutual exclusion in vkbd
>
>
> Alexander Kabaev wrote:
> > 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.
>
> yes, you are correct. my bad :( thanks for catching this
>
> max
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