On Thu, Feb 21, 2013 at 01:09:57PM +0400, Andrey Zonov wrote: A> > Log: A> > Replace splhigh() with critical_enter()/leave() to ensure we write the A> > config mode unlock sequence quickly enough. This likely isn't too critical, A> > since splhigh() has been a noop for a decade... A> > A> > Modified: A> > head/sys/dev/ppc/ppc.c A> > A> > Modified: head/sys/dev/ppc/ppc.c A> > ============================================================================== A> > --- head/sys/dev/ppc/ppc.c Thu Feb 21 00:26:31 2013 (r247065) A> > +++ head/sys/dev/ppc/ppc.c Thu Feb 21 00:27:51 2013 (r247066) A> > @@ -74,6 +74,22 @@ static void ppcintr(void *arg); A> > A> > #define DEVTOSOFTC(dev) ((struct ppc_data *)device_get_softc(dev)) A> > A> > +/* A> > + * We use critical enter/leave for the simple config locking needed to A> > + * detect the devices. We just want to make sure that both of our writes A> > + * happen without someone else also writing to those config registers. Since A> > + * we just do this at startup, Giant keeps multiple threads from executing, A> > + * and critical_enter() then is all that's needed to keep us from being preempted A> > + * during the critical sequences with the hardware. A> > + * A> > + * Note: this doesn't prevent multiple threads from putting the chips into A> > + * config mode, but since we only do that to detect the type at startup the A> > + * extra overhead isn't needed since Giant protects us from multiple entry A> > + * and no other code changes these registers. A> > + */ A> > +#define PPC_CONFIG_LOCK(ppc) critical_enter() A> > +#define PPC_CONFIG_UNLOCK(ppc) critical_leave() A> > + A> A> s/critical_leave/critical_exit/?
Already fixed. However, question to Warner. Since code already executes under Giant, what is the reason for critical_section? What's the problem if couple of outb instructions are split (assuming they are properly serialized) across two CPUs? -- Totus tuus, Glebius. _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
