[Intel Thread Checker 3.1] bogus data race after pthread_once()

• Key: STDCXX-467
• Type: Bug
• Status: Open
• Priority: Major
• Assignee: Unassigned
• Reporter: Martin Sebor
• Component/s: External

Description

Running the program below through the thread checker gives the Wrtite->Read data race error shown in the output:

$ cat t.c && icc -V t.c -pthread && tcheck_cl -v a.out
#include <pthread.h>

static int flag;
static void init () { flag = 1; }

static pthread_once_t flag_init;
static int foo () {
pthread_once (&flag_init, init);
return flag;
}

static void* thr_func (void *a) {
int i;
int n = 0;
for (i = 0; i != 100; ++i)
n += foo ();

return (void*)n;
}

int main () {
pthread_t pid [2];
int i;

for (i = 0; i != sizeof pid / sizeof *pid; ++i)
pthread_create (pid + i, 0, thr_func, 0);

for (i = 0; i != sizeof pid / sizeof *pid; ++i)
pthread_join (pid [i], 0);
}
Intel(R) C Compiler for Intel(R) EM64T-based applications, Version 9.1 Build 20070320 Package ID: l_cc_c_9.1.049
Copyright (C) 1985-2007 Intel Corporation. All rights reserved.

Edison Design Group C/C++ Front End, version 3.6 (Mar 22 2007 02:18:08)
Copyright 1988-2005 Edison Design Group, Inc.

GNU ld version 2.15.92.0.2 20040927
Intel(R) Thread Checker 3.1 command line instrumentation driver (24400)
Copyright (c) 2007 Intel Corporation. All rights reserved.
Building project
Instrumenting
14% a.out ( All Functions ):..

Running: /build/sebor/stdcxx-icc-9.1_049-15S/tests/a.out

Application finished

_______________________________________________________________________________

ID	Short Des	Sever	Co	Contex	Description	1st Ac	2nd Acc
	cription	ity	un	t[Best		cess[B	ess[Bes
		Name	t	]		est]	t]

_______________________________________________________________________________

1	Write ->	Error	10	[a.out	Memory read at [a.out, 0x7b9]	[a.out	[a.out,
	Read		0	,	conflicts with a prior memory	,	0x7b9]
	data-race			0x79a]	write at [a.out, 0x7d0] (flow	0x7d0]
					dependence)

_______________________________________________________________________________

2	Thread te	Infor	1	WholeP	Thread termination at [a.out,	[a.out	[a.out,
	rmination	matio		rogram	0x762] - includes stack	,	0x762]
		n		1	allocation of 10.004 MB and use	0x762]
					of 5.047 KB

_______________________________________________________________________________

3	Thread te	Infor	1	WholeP	Thread termination at [a.out,	[a.out	[a.out,
	rmination	matio		rogram	0x762] - includes stack	,	0x762]
		n		2	allocation of 10.004 MB and use	0x762]
					of 4.984 KB

_______________________________________________________________________________

4	Thread te	Infor	1	WholeP	Thread termination at [a.out,	[a.out	[a.out,
	rmination	matio		rogram	0x728] - includes stack	,	0x728]
		n		3	allocation of 10 MB and use of	0x728]
					1.984 KB

_______________________________________________________________________________