Hi Sébastien,
Sébastien Dugué wrote:
Hello Matthieu,
On Thu, 07 Feb 2008 14:49:07 +0100 Matthieu CASTET <matthieu.castet@xxxxxxxxxx> wrote:
hi,
I am trying to use some IBM rt test on arm.
I define atomic_add to
assert(i==1);
return ++(v->counter);
That's a bit ugly, but that should work for my need.
That would be the poor man's atomic_inc() and not sure it really does
what you think it does ;). Just for the record, pre-armv6 cores have no support
for userland atomic operations (aside from swapping).
I can, if I use a kernel helper :) [1]
BTW what should do the atomic_add.
On i386 it does the atomic add and return the value in memory before the
add (Exchange and Add).
On powerpc, it seems to do the atomic add and return the new value.
But I have a problem with the sched_latency test.
On my platform the thread creation is quite slow (25ms), so with the
default value, I got a PERIOD MISSED.
The IBM RT tests have been integrated into the LTP and I recently
sent some updates to those testcases. Notably one the patches did improve
the thread starting time. Other patches did touch this particular test too.
Could you try the latest release (from LTP) and tell me if things
have improved for you.
Ok I will try them.
Also, the PASS/FAIL criteria are quite arbitrary. They happen to be fine
for most recent PC-class hardware but surely not for embedded systems and
should be tuned according to your RT requirements.
Yes I saw that.
Also my cpu is quite slow (compared to last intel core or powerpc). For
example a sched_jitter run take 6s.
Ouch! What's your CPU (core type, clock speed)?
Arm926 ~104.65 Mhz
Thanks,
Matthieu
[1]
#define __arch_compare_and_exchange_val_32_acq(mem, newval, oldval) \
({ register __typeof (oldval) a_oldval asm ("r0");
\
register __typeof (oldval) a_newval asm ("r1") = (newval);
\
register __typeof (mem) a_ptr asm ("r2") = (mem);
\
register __typeof (oldval) a_tmp asm ("r3");
\
register __typeof (oldval) a_oldval2 asm ("r4") = (oldval);
\
__asm__ __volatile__
\
("0:\tldr\t%[tmp],[%[ptr]]\n\t"
\
"cmp\t%[tmp], %[old2]\n\t"
\
"bne\t1f\n\t"
\
"mov\t%[old], %[old2]\n\t"
\
"mov\t%[tmp], #0xffff0fff\n\t"
\
"mov\tlr, pc\n\t"
\
"add\tpc, %[tmp], #(0xffff0fc0 - 0xffff0fff)\n\t"
\
"bcc\t0b\n\t"
\
"mov\t%[tmp], %[old2]\n\t"
\
"1:"
\
: [old] "=&r" (a_oldval), [tmp] "=&r" (a_tmp)
\
: [new] "r" (a_newval), [ptr] "r" (a_ptr),
\
[old2] "r" (a_oldval2)
\
: "ip", "lr", "cc", "memory");
\
a_tmp; })
do {
int oldval = v->counter;
int ret;
ret = __arch_compare_and_exchange_val_32_acq(&v->counter, oldval+i,
oldval);
} while (ret != oldval);
return oldval;
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