sighook: New utilities for hooking signals

This allows multiple hooks to be installed for a single signal.

3 files changed, 101 insertions, 0 deletions

diff --git a/tests/main.c b/tests/main.c
index 429772b..58def32 100644
--- a/tests/main.c
+++ b/tests/main.c
@@ -116,6 +116,7 @@ int main(int argc, char *argv[]) {
 	run_test(&ctx, "bfstd", check_bfstd);
 	run_test(&ctx, "bit", check_bit);
 	run_test(&ctx, "ioq", check_ioq);
+	run_test(&ctx, "sighook", check_sighook);
 	run_test(&ctx, "trie", check_trie);
 	run_test(&ctx, "xspawn", check_xspawn);
 	run_test(&ctx, "xtime", check_xtime);
diff --git a/tests/sighook.c b/tests/sighook.c
new file mode 100644
index 0000000..e5dd47f
--- /dev/null
+++ b/tests/sighook.c
@@ -0,0 +1,97 @@
+// 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 <pthread.h>
+#include <signal.h>
+#include <sys/time.h>
+
+static atomic size_t count = 0;
+
+/** SIGALRM handler. */
+static void alrm_hook(int sig, siginfo_t *info, void *arg) {
+	fetch_add(&count, 1, relaxed);
+}
+
+/** Swap out an old hook for a new hook. */
+static int swap_hooks(struct sighook **hook) {
+	struct sighook *next = sighook(SIGALRM, alrm_hook, NULL, SH_CONTINUE);
+	if (!bfs_pcheck(next, "sighook(SIGALRM)")) {
+		return -1;
+	}
+
+	sigunhook(*hook);
+	*hook = next;
+	return 0;
+}
+
+/** Background thread that rapidly (un)registers signal hooks. */
+static void *hook_thread(void *ptr) {
+	struct sighook *hook = sighook(SIGALRM, alrm_hook, NULL, SH_CONTINUE);
+	if (!bfs_pcheck(hook, "sighook(SIGALRM)")) {
+		return NULL;
+	}
+
+	while (load(&count, relaxed) < 1000) {
+		if (swap_hooks(&hook) != 0) {
+			sigunhook(hook);
+			return NULL;
+		}
+	}
+
+	sigunhook(hook);
+	return &count;
+}
+
+bool check_sighook(void) {
+	bool ret = true;
+
+	struct sighook *hook = sighook(SIGALRM, alrm_hook, NULL, SH_CONTINUE);
+	ret &= bfs_pcheck(hook, "sighook(SIGALRM)");
+	if (!ret) {
+		goto done;
+	}
+
+	struct itimerval ival = {
+		.it_value = {
+			.tv_usec = 100,
+		},
+		.it_interval = {
+			.tv_usec = 100,
+		},
+	};
+	ret &= bfs_pcheck(setitimer(ITIMER_REAL, &ival, NULL) == 0);
+	if (!ret) {
+		goto unhook;
+	}
+
+	pthread_t thread;
+	ret &= bfs_pcheck(thread_create(&thread, NULL, hook_thread, NULL) == 0);
+	if (!ret) {
+		goto untime;
+	}
+
+	while (ret && load(&count, relaxed) < 1000) {
+		ret &= swap_hooks(&hook) == 0;
+	}
+
+ 	void *ptr;
+	thread_join(thread, &ptr);
+	ret &= bfs_check(ptr);
+
+untime:
+	ival.it_value.tv_usec = 0;
+	ret &= bfs_pcheck(setitimer(ITIMER_REAL, &ival, NULL) == 0);
+	if (!ret) {
+		goto unhook;
+	}
+
+unhook:
+	sigunhook(hook);
+done:
+	return ret;
+}
diff --git a/tests/tests.h b/tests/tests.h
index 9078938..d26a5a0 100644
--- a/tests/tests.h
+++ b/tests/tests.h
@@ -26,6 +26,9 @@ bool check_bit(void);
 /** I/O queue tests. */
 bool check_ioq(void);
 
+/** Signal hook tests. */
+bool check_sighook(void);
+
 /** Trie tests. */
 bool check_trie(void);