Julian, all, any ideas on this?
[ I am sorry for disturbing you... But just in case you've missed this
message...]
--kcc
On Dec 6, 2007 12:23 PM, Konstantin Serebryany
<[EMAIL PROTECTED]>
wrote:
> Hi
> One more question:
>
>
> % cat missed_race.cc
> #include <pthread.h>
> #include <stdio.h>
> #include <unistd.h>
> // In this test we do the following:
> // parent...........................worker
> // 1. pthread_create(worker) a. sleep(sleep_worker)
> // 2. sleep(sleep_parent) b. print(GLOB)
> // 3. GLOB = 1
>
> // The behaviour of helgrind depends on values of
> // sleep_parent/sleep_worker.
> // If the values are close (sleep_parent=1000, sleep_worker=2000),
> // detection of the race actually depends on luck.
> // On my system it is detected 1 of 4-5 of times.
> //
> // If the parent gets to 'GLOB=1' first, then no race is detected.
> // We have Exclusive(parent)->ShR(parent,worker)
> //
> // If the worker gets to print(GLOB) first, then the race is reported.
> // We have Exclusive(worked)->ShM({parent,worker}, {empty lockset})
> //
> // This race should (IMHO) be detected independently of sleep values.
> // Do we need to have ExclusiveR and ExclusiveW instead of just Exclusive?
>
> int GLOB = 0;
> const int sleep_parent=1000;
> const int sleep_worker=2000;
>
> void *worker(void*)
> {
> usleep(sleep_worker);
> printf("GLOB=%d\n", GLOB);
> return NULL;
> }
> int main(int argc, char **argv)
> {
> pthread_t threadid;
> pthread_create(&threadid, NULL, worker, NULL);
> usleep(sleep_parent);
> GLOB = 1;
> pthread_join(threadid, NULL);
> }
>
> /*
> % g++ -g missed_race.cc -lpthread
> % for((i=1; i <= 10; i++)); do echo ---------- $i;
> ~/race/valgrind32orig/Inst/bin/valgrind -q --tool=helgrind ./a.out 2>&1 |
> grep -A 5 Possible; done
> ---------- 1
> ---------- 2
> ---------- 3
> ---------- 4
> ---------- 5
> ---------- 6
> ==13246== Possible data race during write of size 4 at 0x8049850
> ==13246== at 0x8048585: main (missed_race.cc:40)
> ==13246== Old state: owned exclusively by thread #2
> ==13246== New state: shared-modified by threads #1, #2
> ==13246== Reason: this thread, #1, holds no locks at all
> GLOB=0
> ---------- 7
> ---------- 8
> ==13254== Possible data race during write of size 4 at 0x8049850
> ==13254== at 0x8048585: main (missed_race.cc:40)
> ==13254== Old state: owned exclusively by thread #2
> ==13254== New state: shared-modified by threads #1, #2
> ==13254== Reason: this thread, #1, holds no locks at all
> GLOB=0
> ---------- 9
> ---------- 10
> %
> */
>
>
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