[Cbe-oss-dev] [PATCH 2/2] ps3fb: fix deadlock on kexec()

[Geert Uytterhoeven]

On Fri, 11 Jan 2008, Jeremy Kerr wrote:
> > Perhaps ps3fb_release() should do
> >
> > 	if (!try_acquire_console_sem()) {
> > 		ps3fb_sync();
> > 		release_console_sem();
> > 	}
> >
> > This would do the sync on a normal close, but not on special cases
> > (console unbind, e.g. shutdown and kexec).
> >
> > What do you think?
> >
> > BTW, if we want these fixes in 2.6.24, we probably have to send it
> > ASAP (tomorrow?).
> 
> Agreed - either way is fine with me, as long as we can kexec :D
> 
> Perhaps we can do the simple ps3fb fix for .24, then fix the fbmem 
> fb_release calling conventions in .25.

I'll take that road: I think it's safer to let ps3fb_release() try to acquire
the console semaphore and not refresh the screen if it fails, than to call
ps3fb_sync() without holding the console semaphore, as ps3fbpar may get
modified at the same time, causing crashes or lockups.

After all, ps3fb_release() only calls ps3fb_sync() to refresh the screen when
display flipping is disabled, which is an uncommon case (except during
shutdown/kexec).

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Network and Software Technology Center Europe
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