Valgrind – Helgrind – concurrency issue detection.

# Helgrind
http://valgrind.org/docs/manual/hg-manual.html
--tool=helgrind
[root@localhost valgrindTest]# cat simpleDataRace.c
/* Code from Valgrind Manual */
#include <pthread.h>

int var = 0;

void* child_fn ( void* arg ) {
 var++; /* Unprotected relative to parent */ /* this is line 6 */
 return NULL;
}

int main ( void ) {
 pthread_t child;
 pthread_create(&child, NULL, child_fn, NULL);
 var++; /* Unprotected relative to child */ /* this is line 13 */
 pthread_join(child, NULL);
 return 0;
}
[root@localhost valgrindTest]# gcc -Wall -g -lpthread -o simpleDataRace simpleDataRace.c
[root@localhost valgrindTest]# valgrind --tool=helgrind ./simpleDataRace
==5733== Helgrind, a thread error detector
==5733== Copyright (C) 2007-2011, and GNU GPL'd, by OpenWorks LLP et al.
==5733== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==5733== Command: ./simpleDataRace
==5733==
==5733== ---Thread-Announcement------------------------------------------
==5733==
==5733== Thread #1 is the program's root thread
==5733==
==5733== ---Thread-Announcement------------------------------------------
==5733==
==5733== Thread #2 was created
==5733==    at 0x6D8098: clone (in /lib/libc-2.5.so)
==5733==    by 0x400B468: pthread_create_WRK (hg_intercepts.c:255)
==5733==    by 0x400B53D: pthread_create@* (hg_intercepts.c:286)
==5733==    by 0x804849E: main (simpleDataRace.c:12)
==5733==
==5733== ----------------------------------------------------------------
==5733==
==5733== Possible data race during read of size 4 at 0x8049724 by thread #1
==5733== Locks held: none
==5733== at 0x804849F: main (simpleDataRace.c:13)
==5733==
==5733== This conflicts with a previous write of size 4 by thread #2
==5733== Locks held: none
==5733== at 0x804845F: child_fn (simpleDataRace.c:6)
==5733== by 0x400B5B8: mythread_wrapper (hg_intercepts.c:219)
==5733== by 0x798831: start_thread (in /lib/libpthread-2.5.so)
==5733== by 0x6D80AD: clone (in /lib/libc-2.5.so)
==5733==
==5733== ----------------------------------------------------------------
==5733==
==5733== Possible data race during write of size 4 at 0x8049724 by thread #1
==5733== Locks held: none
==5733== at 0x80484A7: main (simpleDataRace.c:13)
==5733==
==5733== This conflicts with a previous write of size 4 by thread #2
==5733== Locks held: none
==5733== at 0x804845F: child_fn (simpleDataRace.c:6)
==5733== by 0x400B5B8: mythread_wrapper (hg_intercepts.c:219)
==5733== by 0x798831: start_thread (in /lib/libpthread-2.5.so)
==5733== by 0x6D80AD: clone (in /lib/libc-2.5.so)
==5733==
==5733==
==5733== For counts of detected and suppressed errors, rerun with: -v
==5733== Use --history-level=approx or =none to gain increased speed, at
==5733== the cost of reduced accuracy of conflicting-access information
==5733== ERROR SUMMARY: 2 errors from 2 contexts (suppressed: 0 from 0)
[root@localhost valgrindTest]#