Re: [BUG] Variable stopmachine_state should be volatile

[Pavel Machek <pavel@ucw.cz>]

Hi!

> >>Hi!
> >>
> >>> The model to access variable stopmachine_state is that a main thread
> >>> writes it and other threads read it. Its declaration has no sign
> >>> volatile. In the while loop in function stopmachine, this variable is
> >>> read, and compiler might optimize it by reading it once before the loop
> >>> and not reading it again in the loop, so the thread might enter dead
> >>> loop.
> >>
> >>No. volatile may look like a solution, but it usually is not. You may
> >>need some barriers, atomic_t or locking.
> >>								Pavel
> The original functions already use smp_mb/smp_wmb. My patch just
>tells compiler not to optimize by bringing the reading of
>stopmachine_state out of the while loop.

Those barriers should already prevent compiler optimalization, no? If
they do not, just use some barriers that do.
								Pavel


-- 
Thanks, Sharp!