As far as I understand, helgrind is not more than just Eraser :)
For example, the following program does not report any race, while GLOB is
*not* protected by any lock.
% cat cv2.cc
#define _MULTI_THREADED
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
static int COND = 0;
static int GLOB = 0;
static pthread_cond_t CV = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t MU = PTHREAD_MUTEX_INITIALIZER;
void *run_pm(void*) {
sleep(2); // we want waiter to get there first
GLOB = 1;
pthread_mutex_lock(&MU);
COND++;
fprintf(stderr, "Signal: COND: %d\n", COND);
pthread_cond_signal(&CV);
pthread_mutex_unlock(&MU);
return NULL;
}
int main() {
pthread_t threadid;
GLOB = 2;
pthread_create(&threadid, NULL, run_pm, NULL);
pthread_mutex_lock(&MU);
while (COND != 1) {
pthread_cond_wait(&CV, &MU);
}
pthread_mutex_unlock(&MU);
GLOB = 2;
fprintf(stderr, "GLOB: %d\n", GLOB);
pthread_join(threadid, NULL);
return 0;
}
% g++ -g cv2.cc -lpthread ; ~/race/valgrind32orig/Inst/bin/valgrind -q
--tool=helgrind ./a.out
Signal: COND: 1
GLOB: 2
%
On Dec 5, 2007 3:10 PM, Bart Van Assche <[EMAIL PROTECTED]> wrote:
> On Dec 5, 2007 10:56 AM, Konstantin Serebryany <
> [EMAIL PROTECTED]> wrote:
>
> > Hi Julian, all,
> >
> > I get a report about a race from helgrind, while everything looks well
> > synchronized to me.
> > Am I wrong?
> >
>
> I can be wrong, but my understanding is that the Eraser algorithm
> (helgrind) reports any conflicting accesses to shared variables that are not
> protected by proper locking, so I expect helgrind to complain on the last
> COND access. DRD on the other hand looks for possible causes of
> nondeterminism. There are no such issues in the program cv.cc, hence DRD
> does not complain on any of the COND accesses in cv.cc.
>
> Regards,
>
> Bart Van Assche.
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