/* Program which uses a happens-before edge to coordinate an access to
variable 'shared_var' between two threads. The h-b edge is created
by a custom (kludgesome!) mechanism and hence we need to use
ANNOTATES_HAPPEN_{BEFORE,AFTER} to explain to Helgrind what's going
on (else it reports a race). */
#include <pthread.h>
#include <stdio.h>
#include <assert.h>
#include "../../helgrind/helgrind.h"
/* Todo: move all this do_acasW guff into a support library. It's
useful for multiple tests, not just this one.
XXX: all the do_acasW routines assume the supplied address
is UWord (naturally) aligned. */
typedef unsigned long int UWord;
#if defined(VGA_ppc64be) || defined(VGA_ppc64le)
// ppc64
/* return 1 if success, 0 if failure */
UWord do_acasW ( UWord* addr, UWord expected, UWord nyu )
{
UWord old, success;
/* Fetch the old value, and set the reservation */
__asm__ __volatile__ (
"ldarx %0, 0,%1" "\n" // rD,rA,rB
: /*out*/ "=b"(old)
: /*in*/ "b"(addr)
: /*trash*/ "memory","cc"
);
/* If the old value isn't as expected, we've had it */
if (old != expected) return 0;
/* otherwise try to stuff the new value in */
__asm__ __volatile__(
"stdcx. %2, 0,%1" "\n" // rS,rA,rB
"mfcr %0" "\n\t"
"srdi %0,%0,29" "\n\t"
"andi. %0,%0,1" "\n"
: /*out*/ "=b"(success)
: /*in*/ "b"(addr), "b"(nyu)
);
assert(success == 0 || success == 1);
return success;
}
#elif defined(VGA_ppc32)
// ppc32
/* return 1 if success, 0 if failure */
UWord do_acasW ( UWord* addr, UWord expected, UWord nyu )
{
UWord old, success;
/* Fetch the old value, and set the reservation */
__asm__ __volatile__ (
"lwarx %0, 0,%1" "\n" // rD,rA,rB
: /*out*/ "=b"(old)
: /*in*/ "b"(addr)
: /*trash*/ "memory","cc"
);
/* If the old value isn't as expected, we've had it */
if (old != expected) return 0;
/* otherwise try to stuff the new value in */
__asm__ __volatile__(
"stwcx. %2, 0,%1" "\n" // rS,rA,rB
"mfcr %0" "\n\t"
"srwi %0,%0,29" "\n\t"
"andi. %0,%0,1" "\n"
: /*out*/ "=b"(success)
: /*in*/ "b"(addr), "b"(nyu)
);
assert(success == 0 || success == 1);
return success;
}
#elif defined(VGA_amd64)
// amd64
/* return 1 if success, 0 if failure */
UWord do_acasW ( UWord* addr, UWord expected, UWord nyu )
{
UWord block[4] = { (UWord)addr, expected, nyu, 2 };
__asm__ __volatile__(
"movq 0(%%rsi), %%rdi" "\n\t" // addr
"movq 8(%%rsi), %%rax" "\n\t" // expected
"movq 16(%%rsi), %%rbx" "\n\t" // nyu
"xorq %%rcx,%%rcx" "\n\t"
"lock; cmpxchgq %%rbx,(%%rdi)" "\n\t"
"setz %%cl" "\n\t"
"movq %%rcx, 24(%%rsi)" "\n"
: /*out*/
: /*in*/ "S"(&block[0])
: /*trash*/"memory","cc","rdi","rax","rbx","rcx"
);
assert(block[3] == 0 || block[3] == 1);
return block[3] & 1;
}
#elif defined(VGA_x86)
// x86
/* return 1 if success, 0 if failure */
UWord do_acasW ( UWord* addr, UWord expected, UWord nyu )
{
UWord block[4] = { (UWord)addr, expected, nyu, 2 };
__asm__ __volatile__(
"pushl %%ebx" "\n\t"
"movl 0(%%esi), %%edi" "\n\t" // addr
"movl 4(%%esi), %%eax" "\n\t" // expected
"movl 8(%%esi), %%ebx" "\n\t" // nyu
"xorl %%ecx,%%ecx" "\n\t"
"lock; cmpxchgl %%ebx,(%%edi)" "\n\t"
"setz %%cl" "\n\t"
"movl %%ecx, 12(%%esi)" "\n\t"
"popl %%ebx" "\n"
: /*out*/
: /*in*/ "S"(&block[0])
: /*trash*/"memory","cc","edi","eax","ecx"
);
assert(block[3] == 0 || block[3] == 1);
return block[3] & 1;
}
#elif defined(VGA_arm)
// arm
/* return 1 if success, 0 if failure */
UWord do_acasW ( UWord* addr, UWord expected, UWord nyu )
{
UWord old, success;
UWord block[2] = { (UWord)addr, nyu };
/* Fetch the old value, and set the reservation */
__asm__ __volatile__ (
"ldrex %0, [%1]" "\n"
: /*out*/ "=r"(old)
: /*in*/ "r"(addr)
);
/* If the old value isn't as expected, we've had it */
if (old != expected) return 0;
/* otherwise try to stuff the new value in */
__asm__ __volatile__(
"ldr r4, [%1, #0]" "\n\t"
"ldr r5, [%1, #4]" "\n\t"
"strex r6, r5, [r4, #0]" "\n\t"
"eor %0, r6, #1" "\n\t"
: /*out*/ "=r"(success)
: /*in*/ "r"(&block[0])
: /*trash*/ "r4","r5","r6","memory"
);
assert(success == 0 || success == 1);
return success;
}
#elif defined(VGA_arm64)
// arm64
/* return 1 if success, 0 if failure */
UWord do_acasW ( UWord* addr, UWord expected, UWord nyu )
{
UWord old, success;
UWord block[2] = { (UWord)addr, nyu };
/* Fetch the old value, and set the reservation */
__asm__ __volatile__ (
"ldxr %0, [%1]" "\n"
: /*out*/ "=r"(old)
: /*in*/ "r"(addr)
);
/* If the old value isn't as expected, we've had it */
if (old != expected) return 0;
/* otherwise try to stuff the new value in */
__asm__ __volatile__(
"ldr x4, [%1, #0]" "\n\t"
"ldr x5, [%1, #8]" "\n\t"
"stxr w6, x5, [x4, #0]" "\n\t"
"eor %0, x6, #1" "\n\t"
: /*out*/ "=r"(success)
: /*in*/ "r"(&block[0])
: /*trash*/ "x4","x5","x6","memory"
);
assert(success == 0 || success == 1);
return success;
}
#elif defined(VGA_s390x)
// s390x
/* return 1 if success, 0 if failure */
UWord do_acasW(UWord* addr, UWord expected, UWord nyu )
{
int cc;
__asm__ __volatile__ (
"csg %2,%3,%1\n\t"
"ipm %0\n\t"
"srl %0,28\n\t"
: /* out */ "=r" (cc)
: /* in */ "Q" (*addr), "d" (expected), "d" (nyu)
: "memory", "cc"
);
return cc == 0;
}
#elif defined(VGA_mips32)
// mips32
/* return 1 if success, 0 if failure */
UWord do_acasW ( UWord* addr, UWord expected, UWord nyu )
{
UWord success;
UWord block[3] = { (UWord)addr, nyu, expected};
__asm__ __volatile__(
".set noreorder" "\n\t"
"lw $t0, 0(%1)" "\n\t"
"lw $t2, 8(%1)" "\n\t"
"lw $t3, 4(%1)" "\n\t"
"ll $t1, 0($t0)" "\n\t"
"bne $t1, $t2, exit_0" "\n\t"
"nop" "\n\t"
"sc $t3, 0($t0)" "\n\t"
"move %0, $t3" "\n\t"
"b exit" "\n\t"
"nop" "\n\t"
"exit_0:" "\n\t"
"move %0, $zero" "\n\t"
"exit:" "\n\t"
: /*out*/ "=r"(success)
: /*in*/ "r"(&block[0])
: /*trash*/ "t0", "t1", "t2", "t3", "memory"
);
assert(success == 0 || success == 1);
return success;
}
#elif defined(VGA_mips64)
// mips64
/* return 1 if success, 0 if failure */
UWord do_acasW ( UWord* addr, UWord expected, UWord nyu )
{
UWord success;
UWord block[3] = { (UWord)addr, nyu, expected};
__asm__ __volatile__(
".set noreorder" "\n\t"
"ld $t0, 0(%1)" "\n\t"
"ld $t2, 16(%1)" "\n\t"
"ld $t3, 8(%1)" "\n\t"
"ll $t1, 0($t0)" "\n\t"
"bne $t1, $t2, exit_0" "\n\t"
"nop" "\n\t"
"sc $t3, 0($t0)" "\n\t"
"move %0, $t3" "\n\t"
"b exit" "\n\t"
"nop" "\n\t"
"exit_0:" "\n\t"
"move %0, $zero" "\n\t"
"exit:" "\n\t"
: /*out*/ "=r"(success)
: /*in*/ "r"(&block[0])
: /*trash*/ "t0", "t1", "t2", "t3", "memory"
);
assert(success == 0 || success == 1);
return success;
}
#elif defined(VGA_tilegx)
/* return 1 if success, 0 if failure */
UWord do_acasW(UWord* addr, UWord expected, UWord nyu )
{
/* Load the compare value into special register 0x2780 */
__insn_mtspr(0x2780, expected);
return __insn_cmpexch(addr, nyu);
}
#endif
void atomic_incW ( UWord* w )
{
while (1) {
UWord old = *w;
UWord nyu = old + 1;
UWord ok = do_acasW( w, old, nyu );
if (ok) break;
};
}
#if 0
#define NNN 1000000
void* thread_fn ( void* arg )
{
UWord* w = (UWord*)arg;
int i;
for (i = 0; i < NNN; i++)
atomic_incW( w );
return NULL;
}
int main ( void )
{
int r;
//ANNOTATE_HAPPENS_BEFORE(0);
//return 0;
UWord w = 0;
pthread_t t1, t2;
r= pthread_create( &t1, NULL, &thread_fn, (void*)&w ); assert(!r);
r= pthread_create( &t2, NULL, &thread_fn, (void*)&w ); assert(!r);
r= pthread_join( t1, NULL ); assert(!r);
r= pthread_join( t2, NULL ); assert(!r);
printf("result = %lu\n", w );
return 0;
}
#endif
int shared_var = 0; // is not raced upon
void delayXms ( int i )
{
struct timespec ts = { 0, 1 * 1000 * 1000 };
// We do the sleep in small pieces to have scheduling
// events ensuring a fair switch between threads, even
// without --fair-sched=yes. This is a.o. needed for
// running this test under an outer helgrind or an outer
// sgcheck.
while (i > 0) {
nanosleep(&ts, NULL);
i--;
}
}
void do_wait ( UWord* w )
{
UWord w0 = *w;
UWord volatile * wV = w;
while (*wV == w0)
delayXms(1); // small sleeps, ensuring context switches
ANNOTATE_HAPPENS_AFTER(w);
}
void do_signal ( UWord* w )
{
ANNOTATE_HAPPENS_BEFORE(w);
atomic_incW(w);
}
void* thread_fn1 ( void* arg )
{
UWord* w = (UWord*)arg;
delayXms(500); // ensure t2 gets to its wait first
shared_var = 1; // first access
do_signal(w); // cause h-b edge to second thread
delayXms(500);
return NULL;
}
void* thread_fn2 ( void* arg )
{
UWord* w = (UWord*)arg;
do_wait(w); // wait for h-b edge from first thread
shared_var = 2; // second access
delayXms(500);
return NULL;
}
int main ( void )
{
int r;
UWord w = 0;
pthread_t t1, t2;
r= pthread_create( &t1, NULL, &thread_fn1, (void*)&w ); assert(!r);
r= pthread_create( &t2, NULL, &thread_fn2, (void*)&w ); assert(!r);
r= pthread_join( t1, NULL ); assert(!r);
r= pthread_join( t2, NULL ); assert(!r);
return 0;
}