Hi,
On Mon, 19 Jan 2015 18:49:21, Konstantin Serebryany wrote:
>
> [text-only]
>
> On Mon, Jan 19, 2015 at 7:42 AM, Mike Stump <mikest...@comcast.net> wrote:
>> On Jan 19, 2015, at 12:43 AM, Dmitry Vyukov <dvyu...@google.com> wrote:
>>> I can't really make my mind on this. I would mildly prefer sleep's (if
>>> they work reliably!).
>>
>> Let me state it more forcefully.
> You don't have to convince us here.
> I'd love to get rid of sleep calls in the tsan test suite -- they are
> a minor but a constant annoyance.
> But I also want to keep the tests *very simple*, i.e.
> 1. Single file w/o any non-system includes, no linking of extra
> libraries/objects
> 2. Not too much extra code. (ideally, 1 line for init, 1 line for
> "signal", 1 line for "wait")
> 3. Strictly posix or c++11 (unless we are testing something specific)
>
> Your idea with barrier_wait/dlsym sounds interesting, but I can't see
> the code in this mail thread.
> What do I miss?
>
We discussed two alternatives to sleep:
1. step function, optionally with sched_yield to make it somewhat less busy
waiting:
__attribute__((no_sanitize_thread))
void step (int i)
{
while (__atomic_load_n (&serial, __ATOMIC_ACQUIRE) != i - 1)
sched_yield();
__atomic_store_n (&serial, i, __ATOMIC_RELEASE);
}
2. tsan-invisible barriers:
cat tsan_barrier.h
/* TSAN-invisible barriers. Link with -ldl. */
#include <pthread.h>
#include <dlfcn.h>
static __typeof(pthread_barrier_wait) *barrier_wait;
static
void barrier_init (pthread_barrier_t *barrier, unsigned count)
{
void *h = dlopen ("libpthread.so.0", RTLD_LAZY);
barrier_wait = (__typeof (pthread_barrier_wait) *)
dlsym (h, "pthread_barrier_wait");
pthread_barrier_init (barrier, NULL, count);
}
We preferred the second alternative, because it does not do busy waiting.
We include this header file in every positive test case and link with -ldl.
Bernd.
