Re: get_current is __pure__, maybe __const__ even

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Thu, Sep 16, 2004 at 11:11:28AM +0200, Andi Kleen wrote:
> > IOW, think from a tasks point of view.  It gets into the scheduler,
> > and switch_to() is just a normal function which just happens to sleep
> > for some time.
> 
> On x86/x86-64 the stack switch is inlined into schedule() 

Yes, and does it not save the whole CPU context and restore it, or tell
the compiler that certain registers which you don't preserve are
clobbered?  If it didn't, I think you'd find that you have a bug
there.

The scheduler quite rightly expects, for any thread, that any variable
which may be stored in a CPU register before the context switch has the
same value as after the context switch.

(note - "preserve" above - I don't mean from one thread to another,
I mean preserved within the context of one thread.)

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 PCMCIA      - http://pcmcia.arm.linux.org.uk/
                 2.6 Serial core