Ralf,
Thanks for the help. I generally consider myself a pseudo-expert on
Linux, but at the same time I'm amazed by how much I learn on a daily basis.
So I've got the following code which seems to work... (I can't use the
ll/sc ops on the Vr41xx since they are not implemeted!)
#ifdef CONFIG_CPU_VR41XX
/* this version is inherently single processor! */
case MIPS_ATOMIC_SET: {
unsigned int tmp;
unsigned long flags;
p = (int *) arg1;
errno = verify_area(VERIFY_WRITE, p, sizeof(*p));
if (errno)
return errno;
errno = 0;
/* the Vr processors can't be SMP, so just lock ints */
save_and_cli(flags);
tmp = *p ;
*p = arg2 ;
restore_flags(flags);
return tmp;
}
#endif
The trailer in the normal call is like :
/* We're skipping error handling etc. */
if (current->ptrace & PT_TRACESYS)
syscall_trace();
__asm__ __volatile__(
"move\t$29, %0\n\t"
"j\tret_from_sys_call"
: /* No outputs */
: "r" (&cmd));
/* Unreached */
Which says "no outputs" although sysmips is specified as
extern int sysmips __P ((__const cmd, __const int arg1,
__const int arg2, __const int arg3));
and the usage of this call in glibc pthreads implies that there should
be a return value. Should I be bypassing the scheduler to return also?
The end goal of this is to make pthreads work on the Vr4181...it's
certainly an interesting task so far...
Ralf Baechle wrote:
> On Thu, Jan 25, 2001 at 01:35:23PM -0600, Joe deBlaquiere wrote:
>
>
>> sysmips(MIPS_ATOMIC_SET,ptr,val)
>> {
>> *ptr = val ;
>> val 0 ;
>> }
>>
>> but it is an atomic operation
>>
>> if this correct in a pseudo-code sense?
>
>
> It's more:
>
> sysmips(MIPS_ATOMIC_SET, ptr, val)
> {
> result = *ptr;
> *ptr = val;
>
> return result;
> }
>
> Ralf
--
Joe deBlaquiere
Red Hat, Inc.
307 Wynn Drive
Huntsville AL, 35805
voice : (256)-704-9200
fax : (256)-837-3839
