Hi,
I likely found a problem in the DRD when using the --free-is-write
option. The following test case reports an huge amount of errors that
are not expected.
Valgrind and helgrind report no error.
The machine is a Ubuntu 10.4 x86 with valgrind 3.6.0 compiled from source.
The program is compiled with: gcc -O1 -g -D_REENTRANT multi.c -o
multi -lpthread
In a big application I have similar strange reports, even without
using --free-is-write, so maybe --free-is-write is only a way to
expose the bug.
Here the C program:
#include <pthread.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <string.h>
static pthread_mutex_t thread_mutex = PTHREAD_MUTEX_INITIALIZER;
unsigned term_count;
#define SIZE 22816
#define N 10
#define M 1000
void* thread_func(void* arg)
{
unsigned i;
for(i=0;i<M;++i) {
void* ptr;
printf("a");
ptr = malloc(SIZE);
printf("s");
memset(ptr, 0, SIZE);
printf("f");
free(ptr);
}
pthread_mutex_lock(&thread_mutex);
++term_count;
pthread_mutex_unlock(&thread_mutex);
pthread_exit(NULL);
return 0;
}
int main(int argc, char **argv)
{
pthread_t thread;
int i;
for (i=0;i<N; i++ ) {
if (pthread_create(&thread, 0, thread_func, 0) != 0) {
abort();
}
}
while (1) {
unsigned curr_term;
pthread_mutex_lock(&thread_mutex);
curr_term = term_count;
pthread_mutex_unlock(&thread_mutex);
if (curr_term == N)
break;
sleep(1);
}
return 0;
}
Here the DRD report:
==391== drd, a thread error detector
==391== Copyright (C) 2006-2010, and GNU GPL'd, by Bart Van Assche.
==391== Using Valgrind-3.6.0 and LibVEX; rerun with -h for copyright info
==391== Command: ./multi
==391==
--391-- Valgrind options:
--391-- --tool=drd
--391-- --free-is-write=yes
--391-- -v
--391-- Contents of /proc/version:
--391-- Linux version 2.6.32-27-generic (buildd@roseapple) (gcc
version 4.4.3 (Ubuntu 4.4.3-4ubuntu5) ) #49-Ubuntu SMP Wed Dec 1
23:52:12 UTC 2010
--391-- Arch and hwcaps: X86, x86-sse1-sse2
--391-- Page sizes: currently 4096, max supported 4096
--391-- Valgrind library directory: /usr/local/lib/valgrind
--391-- Reading syms from /lib/ld-2.11.1.so (0x4000000)
--391-- Considering /lib/ld-2.11.1.so ..
--391-- .. CRC mismatch (computed d005eb74 wanted 53dc8daf)
--391-- Considering /usr/lib/debug/lib/ld-2.11.1.so ..
--391-- .. CRC is valid
--391-- Reading syms from
/home/am/Desktop/drm/api/debugnix/test_drd/multi (0x8048000)
--391-- Reading syms from /usr/local/lib/valgrind/drd-x86-linux (0x38000000)
--391-- object doesn't have a dynamic symbol table
--391-- Reading suppressions file: /usr/local/lib/valgrind/default.supp
--391-- Reading syms from
/usr/local/lib/valgrind/vgpreload_core-x86-linux.so (0x401f000)
--391-- Reading syms from
/usr/local/lib/valgrind/vgpreload_drd-x86-linux.so (0x4022000)
--391-- REDIR: 0x4016290 (strlen) redirected to 0x402ff60 (strlen)
--391-- Reading syms from /lib/tls/i686/cmov/libpthread-2.11.1.so (0x4050000)
--391-- Considering /lib/tls/i686/cmov/libpthread-2.11.1.so ..
--391-- .. CRC mismatch (computed 38da17dd wanted d3835c81)
--391-- Considering /usr/lib/debug/lib/tls/i686/cmov/libpthread-2.11.1.so ..
--391-- .. CRC is valid
--391-- Reading syms from /lib/tls/i686/cmov/libc-2.11.1.so (0x406a000)
--391-- Considering /lib/tls/i686/cmov/libc-2.11.1.so ..
--391-- .. CRC mismatch (computed da84aea3 wanted 8ac7aa97)
--391-- Considering /usr/lib/debug/lib/tls/i686/cmov/libc-2.11.1.so ..
--391-- .. CRC is valid
--391-- REDIR: 0x4055d70 (pthread_create@@GLIBC_2.1) redirected to
0x402d5a0 (pthread_create@*)
--391-- REDIR: 0x40d9660 (calloc) redirected to 0x402610f (calloc)
--391-- REDIR: 0x40d9f40 (malloc) redirected to 0x4026e2b (malloc)
--391-- REDIR: 0x40d9e60 (free) redirected to 0x4026a45 (free)
--391-- REDIR: 0x4057f10 (pthread_mutex_lock) redirected to 0x402e0b0
(pthread_mutex_lock)
--391-- REDIR: 0x4059400 (pthread_mutex_unlock) redirected to
0x402eb60 (pthread_mutex_unlock)
--391-- Reading syms from /lib/libgcc_s.so.1 (0x47e3000)
--391-- Considering /lib/libgcc_s.so.1 ..
--391-- .. CRC mismatch (computed 75b2cc22 wanted fffc9534)
--391-- object doesn't have a symbol table
--391-- REDIR: 0x40dd730 (strlen) redirected to 0x401f44c (_vgnU_ifunc_wrapper)
--391-- REDIR: 0x40dd770 (__strlen_sse2) redirected to 0x402ff40 (strlen)
--391-- REDIR: 0x405b3a0 (pthread_once) redirected to 0x4027f70 (pthread_once)
==391== Thread 3:
==391== Conflicting store by thread 3 at 0x043c6550 size 22816
==391== at 0x4026ACA: free (vg_replace_malloc.c:366)
==391== by 0x804878A: thread_func (multi.c:33)
==391== by 0x402DAAB: vgDrd_thread_wrapper (drd_pthread_intercepts.c:281)
==391== by 0x405596D: start_thread (pthread_create.c:300)
==391== by 0x4137A4D: clone (clone.S:130)
==391== Allocation context: unknown.
==391== Other segment start (thread 2)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 2)
==391== (thread finished, call stack no longer available)
==391==
==391==
==391== ERROR SUMMARY: 8000 errors from 1 contexts (suppressed:
12190873 from 195)
==391==
==391== 8000 errors in context 1 of 1:
==391== Conflicting store by thread 3 at 0x043c6550 size 22816
==391== at 0x4026ACA: free (vg_replace_malloc.c:366)
==391== by 0x804878A: thread_func (multi.c:33)
==391== by 0x402DAAB: vgDrd_thread_wrapper (drd_pthread_intercepts.c:281)
==391== by 0x405596D: start_thread (pthread_create.c:300)
==391== by 0x4137A4D: clone (clone.S:130)
==391== Address 0x43c6550 is at offset 0 from 0x43c6550. Allocation context:
==391== at 0x40261EF: calloc (vg_replace_malloc.c:467)
==391== by 0x4010CDB: _dl_allocate_tls (dl-tls.c:300)
==391== by 0x40562E2: pthread_create@@GLIBC_2.1 (allocatestack.c:561)
==391== by 0x402D6D4: pthread_create@* (drd_pthread_intercepts.c:416)
==391== by 0x80486C3: main (multi.c:51)
==391== Other segment start (thread 1)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 1)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 1)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 1)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 1)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 1)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 1)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 1)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 1)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 1)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 2)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 2)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 4)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 4)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 5)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 5)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 6)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 6)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 7)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 7)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 8)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 8)
==391== (thread finished, call stack no longer available)
==391== Other segment start (thread 9)
==391== (thread finished, call stack no longer available)
==391== Other segment end (thread 9)
==391== (thread finished, call stack no longer available)
==391==
--391--
--391-- used_suppression: 66 drd-ld
--391-- used_suppression: 12190789 drd-libc-stdio
--391-- used_suppression: 18 drd-libpthread-_Unwind_ForcedUnwind
==391==
==391== ERROR SUMMARY: 8000 errors from 1 contexts (suppressed:
12190873 from 195)
Ciao,
Andrea
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