Re: Patch for nvidia-driver on current (panic: spin locks can only use msleep_spin)

On Tuesday 02 October 2007 04:48:57 pm Craig Boston wrote:
> Hi all, I did some more investigating and found what was causing the
> nvidia driver to occasionally panic on my machine.  It calls cv_wait(9)
> using a spin mutex, which according to the man page is a no-no.
> 
> I simply changed the os_*_sema interfaces to use a standard mutex
> instead.  Tried running a bunch of glxgears and xscreensaver GL demos in
> parallel and haven't been able to reproduce a panic since.  As a bonus,
> the 5 second pause I would sometimes get when a GL-based xscreensaver
> process terminates seems to be gone as well.
> 
> There doesn't appear to be any documentation that I could find as to
> what contexts those functions may be called from.  I'm not a locking
> guru, so I can't say for certain why a spin mutex was being used.  Wild
> guess: an artifact from the 4.x or 5.x code that may be obsoleted by
> adaptive mutexes.
> 
> Patch is attached; cc danfe_at_ in case others report this problem to him.

Your patch is good, and I think nvidia is going to fix their driver to use a 
regular mutex as well.  It probably uses a spin mutex because on other OS's 
you have to use a spin mutex to protect data shared with an interrupt 
handler.  However, in the case of FreeBSD, you only use a spin mutex if you 
use an INTR_FAST/filter handler, and can use a regular mutex otherwise.

-- 
John Baldwin