[Fwd: Bug: 2.2.12 still hangs PPC after some PPP activity]

[Geert Uytterhoeven]

	Hi Lou,
	
> > > What might happen if a driver does:
> >
> > point A
> >
> > > save_flags(old_flags);
> > > cli();
> > > restore_flags(old_flags);
> 
> point A2?
> 
> > > save_flags(new_flags);
> > > cli();
> > > restore_flags(new_flags);
> >
> > point B
> >
> > > /* can't we be interupted here? Assume yes, if so */
> > > restore_flags(old_flags);
> >
> > point C

point A == point A2 == point B == point C

> > > . . .Opinions??? Please clue me in anyway... this stuff's a kick! :-)
> >
> > The interrupt mask register has the same contents at points A, B and C. Hence,
> > if we could be interrupt a point A, we can be interrupt at points B and C. . . .
> 
> Looking in macserial.c's rs_write() function it can call transmit_chars(info) at
> point B which would seem to me to be able to be a point at which the interupt mask
> register could change. No? I have to admit I'm only now reading the various docs
> on kernel locks. So I just email'd you hoping you'd give me another hint ;-)

I don't know how the serial port hardware has to be programmed. But if
transmit_chars() must be called with interrupts disabled, it's indeed a bug.

Greetings,

						Geert

--
Geert Uytterhoeven ----------------- Sony Suprastructure Center Europe (SUPC-E)
Geert.Uytterhoeven at sonycom.com ------------------- Sint Stevens Woluwestraat 55
Phone +32-2-7248648 Fax +32-2-7262686 ---------------- B-1130 Brussels, Belgium


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