On Tue, Nov 29, 2022 at 09:54:13AM +0100, David Hildenbrand wrote:
> On 29.11.22 00:48, Ilya Leoshkevich wrote:
> > Add a simple test to prevent regressions.
> >
> > Signed-off-by: Ilya Leoshkevich <i...@linux.ibm.com>
> > ---
> > tests/tcg/s390x/Makefile.target | 4 ++
> > tests/tcg/s390x/cdsg.c | 73 +++++++++++++++++++++++++++++++++
> > 2 files changed, 77 insertions(+)
> > create mode 100644 tests/tcg/s390x/cdsg.c
> >
> > diff --git a/tests/tcg/s390x/Makefile.target
> > b/tests/tcg/s390x/Makefile.target
> > index 1d454270c0e..523214dac33 100644
> > --- a/tests/tcg/s390x/Makefile.target
> > +++ b/tests/tcg/s390x/Makefile.target
> > @@ -27,6 +27,7 @@ TESTS+=noexec
> > TESTS+=div
> > TESTS+=clst
> > TESTS+=long-double
> > +TESTS+=cdsg
> > Z13_TESTS=vistr
> > $(Z13_TESTS): CFLAGS+=-march=z13 -O2
> > @@ -66,3 +67,6 @@ sha512-mvx: sha512.c
> > $(CC) $(CFLAGS) $(EXTRA_CFLAGS) $< -o $@ $(LDFLAGS)
> > TESTS+=sha512-mvx
> > +
> > +cdsg: CFLAGS+=-pthread
> > +cdsg: LDFLAGS+=-pthread
> > diff --git a/tests/tcg/s390x/cdsg.c b/tests/tcg/s390x/cdsg.c
> > new file mode 100644
> > index 00000000000..83313699f7d
> > --- /dev/null
> > +++ b/tests/tcg/s390x/cdsg.c
> > @@ -0,0 +1,73 @@
> > +#include <assert.h>
> > +#include <pthread.h>
> > +#include <stdbool.h>
> > +#include <stdlib.h>
> > +
> > +static volatile bool start;
> > +static unsigned long val[2] __attribute__((__aligned__(16)));
> > +
> > +void *cdsg_loop(void *arg)
> > +{
> > + unsigned long orig0, orig1, new0, new1;
> > + register unsigned long r0 asm("r0");
> > + register unsigned long r1 asm("r1");
> > + register unsigned long r2 asm("r2");
> > + register unsigned long r3 asm("r3");
> > + int cc;
> > + int i;
> > +
> > + while (!start) {
> > + }
> > +
> > + orig0 = val[0];
> > + orig1 = val[1];
> > + for (i = 0; i < 1000;) {
>
> Are 1000 iterations sufficient to catch the race window reliably?
Good point, I had to raise it to 10k.
If I break the code like this:
--- a/tcg/tcg-op.c
+++ b/tcg/tcg-op.c
@@ -3509,7 +3509,7 @@ void tcg_gen_atomic_cmpxchg_i128(TCGv_i128 retv, TCGv
addr, TCGv_i128 cmpv,
{
gen_atomic_cx_i128 gen;
- if (!(tcg_ctx->tb_cflags & CF_PARALLEL)) {
+ if (true) {
tcg_gen_nonatomic_cmpxchg_i128(retv, addr, cmpv, newv, idx, memop);
return;
}
the test with 10k iterations fails consistently.
And it's still fast:
$ time -p ./qemu-s390x ./tests/tcg/s390x-linux-user/cdsg
real 0.01
> > + new0 = orig0 + 1;
> > + new1 = orig1 + 2;
> > +
> > + r0 = orig0;
> > + r1 = orig1;
> > + r2 = new0;
> > + r3 = new1;
> > + asm("cdsg %[r0],%[r2],%[db2]\n"
> > + "ipm %[cc]"
> > + : [r0] "+r" (r0)
> > + , [r1] "+r" (r1)
> > + , [db2] "=m" (val)
> > + , [cc] "=r" (cc)
> > + : [r2] "r" (r2)
> > + , [r3] "r" (r3)
> > + : "cc");
>
> Nit: I'd suggest a simple cdsg helper function that makes this code easier
> to digest.
Ok.
>
> > + orig0 = r0;
> > + orig1 = r1;
> > + cc = (cc >> 28) & 3;
> > +
> > + if (cc == 0) {
> > + orig0 = new0;
> > + orig1 = new1;
> > + i++;
> > + } else {
> > + assert(cc == 1);
> > + }
> > + }
> > +
> > + return NULL;
> > +}
> > +
> > +int main(void)
> > +{
> > + pthread_t thread;
> > + int ret;
> > +
> > + ret = pthread_create(&thread, NULL, cdsg_loop, NULL);
> > + assert(ret == 0);
> > + start = true;
> > + cdsg_loop(NULL);
> > + ret = pthread_join(thread, NULL);
> > + assert(ret == 0);
> > +
> > + assert(val[0] == 2000);
> > + assert(val[1] == 4000);
> > +
> > + return EXIT_SUCCESS;
> > +}
>
> --
> Thanks,
>
> David / dhildenb
>
>
