Use C11 atomics instead of atomic_decrement_and_test

Replace atomic_decrement_and_test with atomic_fetch_add_relaxed.
These are simple counters which do not protect any shared data from
concurrent accesses. Also remove the unused file cond-perf.c.

Passes regress on AArch64.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Wilco Dijkstra 2022-09-22 15:40:37 +01:00
parent d1babeb32d
commit 4a07fbb689
6 changed files with 5 additions and 108 deletions

View File

@ -33,7 +33,7 @@ extern pthread_mutex_t __pthread_free_threads_lock;
void void
__pthread_dealloc (struct __pthread *pthread) __pthread_dealloc (struct __pthread *pthread)
{ {
if (!atomic_decrement_and_test (&pthread->nr_refs)) if (atomic_fetch_add_relaxed (&pthread->nr_refs, -1) != 1)
return; return;
/* Withdraw this thread from the thread ID lookup table. */ /* Withdraw this thread from the thread ID lookup table. */

View File

@ -50,7 +50,7 @@ __pthread_exit (void *status)
/* Decrease the number of threads. We use an atomic operation to /* Decrease the number of threads. We use an atomic operation to
make sure that only the last thread calls `exit'. */ make sure that only the last thread calls `exit'. */
if (atomic_decrement_and_test (&__pthread_total)) if (atomic_fetch_add_relaxed (&__pthread_total, -1) == 1)
/* We are the last thread. */ /* We are the last thread. */
exit (0); exit (0);

View File

@ -2614,7 +2614,7 @@ aiocb64}, since the LFS transparently replaces the old interface.
@c free @ascuheap @acsmem @c free @ascuheap @acsmem
@c libc_thread_freeres @c libc_thread_freeres
@c libc_thread_subfreeres ok @c libc_thread_subfreeres ok
@c atomic_decrement_and_test ok @c atomic_fetch_add_relaxed ok
@c td_eventword ok @c td_eventword ok
@c td_eventmask ok @c td_eventmask ok
@c atomic_compare_exchange_bool_acq ok @c atomic_compare_exchange_bool_acq ok

View File

@ -1,103 +0,0 @@
#include <pthread.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <atomic.h>
static pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t mut1 = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond2 = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t mut2 = PTHREAD_MUTEX_INITIALIZER;
static bool last_round;
static int ntogo;
static bool alldone;
static void *
cons (void *arg)
{
pthread_mutex_lock (&mut1);
do
{
if (atomic_decrement_and_test (&ntogo))
{
pthread_mutex_lock (&mut2);
alldone = true;
pthread_cond_signal (&cond2);
pthread_mutex_unlock (&mut2);
}
pthread_cond_wait (&cond1, &mut1);
}
while (! last_round);
pthread_mutex_unlock (&mut1);
return NULL;
}
int
main (int argc, char *argv[])
{
int opt;
int err;
int nthreads = 10;
int nrounds = 100;
bool keeplock = false;
while ((opt = getopt (argc, argv, "n:r:k")) != -1)
switch (opt)
{
case 'n':
nthreads = atol (optarg);
break;
case 'r':
nrounds = atol (optarg);
break;
case 'k':
keeplock = true;
break;
}
ntogo = nthreads;
pthread_t th[nthreads];
int i;
for (i = 0; __builtin_expect (i < nthreads, 1); ++i)
if (__glibc_unlikely ((err = pthread_create (&th[i], NULL, cons, (void *) (long) i)) != 0))
printf ("pthread_create: %s\n", strerror (err));
for (i = 0; __builtin_expect (i < nrounds, 1); ++i)
{
pthread_mutex_lock (&mut2);
while (! alldone)
pthread_cond_wait (&cond2, &mut2);
pthread_mutex_unlock (&mut2);
pthread_mutex_lock (&mut1);
if (! keeplock)
pthread_mutex_unlock (&mut1);
ntogo = nthreads;
alldone = false;
if (i + 1 >= nrounds)
last_round = true;
pthread_cond_broadcast (&cond1);
if (keeplock)
pthread_mutex_unlock (&mut1);
}
for (i = 0; i < nthreads; ++i)
if ((err = pthread_join (th[i], NULL)) != 0)
printf ("pthread_create: %s\n", strerror (err));
return 0;
}

View File

@ -489,7 +489,7 @@ start_thread (void *arg)
the breakpoint reports TD_THR_RUN state rather than TD_THR_ZOMBIE. */ the breakpoint reports TD_THR_RUN state rather than TD_THR_ZOMBIE. */
atomic_fetch_or_relaxed (&pd->cancelhandling, EXITING_BITMASK); atomic_fetch_or_relaxed (&pd->cancelhandling, EXITING_BITMASK);
if (__glibc_unlikely (atomic_decrement_and_test (&__nptl_nthreads))) if (__glibc_unlikely (atomic_fetch_add_relaxed (&__nptl_nthreads, -1) == 1))
/* This was the last thread. */ /* This was the last thread. */
exit (0); exit (0);

View File

@ -65,7 +65,7 @@ __libc_start_call_main (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
/* One less thread. Decrement the counter. If it is zero we /* One less thread. Decrement the counter. If it is zero we
terminate the entire process. */ terminate the entire process. */
result = 0; result = 0;
if (! atomic_decrement_and_test (&__nptl_nthreads)) if (atomic_fetch_add_relaxed (&__nptl_nthreads, -1) != 1)
/* Not much left to do but to exit the thread, not the process. */ /* Not much left to do but to exit the thread, not the process. */
while (1) while (1)
INTERNAL_SYSCALL_CALL (exit, 0); INTERNAL_SYSCALL_CALL (exit, 0);