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// Copyright © Tavian Barnes <tavianator@tavianator.com>
// SPDX-License-Identifier: 0BSD
#include "prelude.h"
#include "tests.h"
#include "sighook.h"
#include "atomic.h"
#include "thread.h"
#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <sys/time.h>
/** Counts SIGALRM deliveries. */
static atomic size_t count = 0;
/** Keeps the background thread alive. */
static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
static bool done = false;
/** SIGALRM handler. */
static void alrm_hook(int sig, siginfo_t *info, void *arg) {
fetch_add(&count, 1, relaxed);
}
/** Background thread that receives signals. */
static void *hook_thread(void *ptr) {
mutex_lock(&mutex);
while (!done) {
cond_wait(&cond, &mutex);
}
mutex_unlock(&mutex);
return NULL;
}
/** Block a signal in this thread. */
static int block_signal(int sig, sigset_t *old) {
sigset_t set;
if (sigemptyset(&set) != 0) {
return -1;
}
if (sigaddset(&set, sig) != 0) {
return -1;
}
errno = pthread_sigmask(SIG_BLOCK, &set, old);
if (errno != 0) {
return -1;
}
return 0;
}
void check_sighook(void) {
struct sighook *hook = sighook(SIGALRM, alrm_hook, NULL, SH_CONTINUE);
if (!bfs_echeck(hook, "sighook(SIGALRM)")) {
return;
}
// Create a timer that sends SIGALRM every 100 microseconds
struct itimerval ival = {0};
ival.it_value.tv_usec = 100;
ival.it_interval.tv_usec = 100;
if (!bfs_echeck(setitimer(ITIMER_REAL, &ival, NULL) == 0)) {
goto unhook;
}
// Create a background thread to receive signals
pthread_t thread;
if (!bfs_echeck(thread_create(&thread, NULL, hook_thread, NULL) == 0)) {
goto untime;
}
// Block SIGALRM in this thread so the handler runs concurrently with
// sighook()/sigunhook()
sigset_t mask;
if (!bfs_echeck(block_signal(SIGALRM, &mask) == 0)) {
goto untime;
}
// Rapidly register/unregister SIGALRM hooks
while (load(&count, relaxed) < 1000) {
struct sighook *next = sighook(SIGALRM, alrm_hook, NULL, SH_CONTINUE);
if (!bfs_echeck(next, "sighook(SIGALRM)")) {
break;
}
sigunhook(hook);
hook = next;
}
// Quit the background thread
mutex_lock(&mutex);
done = true;
mutex_unlock(&mutex);
cond_signal(&cond);
thread_join(thread, NULL);
// Restore the old signal mask
errno = pthread_sigmask(SIG_SETMASK, &mask, NULL);
bfs_echeck(errno == 0, "pthread_sigmask()");
untime:
// Stop the timer
ival.it_value.tv_usec = 0;
bfs_echeck(setitimer(ITIMER_REAL, &ival, NULL) == 0);
unhook:
// Unregister the SIGALRM hook
sigunhook(hook);
}
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