1 files changed, 109 insertions, 0 deletions
diff --git a/src/thread/synccall.c b/src/thread/synccall.c
new file mode 100644
index 00000000..7c4f92bf
--- /dev/null
+++ b/src/thread/synccall.c
@@ -0,0 +1,109 @@
+#include "pthread_impl.h"
+#include <semaphore.h>
+
+static struct chain {
+	struct chain *next;
+	sem_t sem, sem2;
+} *head;
+
+static void (*callback)(void *), *context;
+static int chainlen;
+static sem_t chainlock, chaindone;
+static pthread_rwlock_t lock = PTHREAD_RWLOCK_INITIALIZER;
+
+static void handler(int sig, siginfo_t *si, void *ctx)
+{
+	struct chain ch;
+	pthread_t self = __pthread_self();
+	int old_errno = errno;
+
+	if (chainlen == libc.threads_minus_1) return;
+
+	sigqueue(self->pid, SIGSYNCCALL, (union sigval){0});
+
+	/* Threads which have already decremented themselves from the
+	 * thread count must not act. Block further receipt of signals
+	 * and return. */
+	if (self->dead) {
+		memset(&((ucontext_t *)ctx)->uc_sigmask, -1, 8);
+		errno = old_errno;
+		return;
+	}
+
+	sem_init(&ch.sem, 0, 0);
+	sem_init(&ch.sem2, 0, 0);
+
+	while (sem_wait(&chainlock));
+	ch.next = head;
+	head = &ch;
+	if (++chainlen == libc.threads_minus_1) sem_post(&chaindone);
+	sem_post(&chainlock);
+
+	while (sem_wait(&ch.sem));
+	callback(context);
+	sem_post(&ch.sem2);
+	while (sem_wait(&ch.sem));
+
+	errno = old_errno;
+}
+
+void __synccall(void (*func)(void *), void *ctx)
+{
+	pthread_t self;
+	struct sigaction sa;
+	struct chain *cur, *next;
+	uint64_t oldmask;
+
+	pthread_rwlock_wrlock(&lock);
+
+	__syscall(SYS_rt_sigprocmask, SIG_BLOCK, (uint64_t[]){-1}, &oldmask, 8);
+
+	if (!libc.threads_minus_1) {
+		func(ctx);
+		return;
+	}
+
+	sem_init(&chaindone, 0, 0);
+	sem_init(&chainlock, 0, 1);
+	chainlen = 0;
+	callback = func;
+	context = ctx;
+
+	sa.sa_flags = SA_SIGINFO | SA_RESTART;
+	sa.sa_sigaction = handler;
+	sigfillset(&sa.sa_mask);
+	__libc_sigaction(SIGSYNCCALL, &sa, 0);
+
+	self = __pthread_self();
+	sigqueue(self->pid, SIGSYNCCALL, (union sigval){0});
+	while (sem_wait(&chaindone));
+
+	for (cur=head; cur; cur=cur->next) {
+		sem_post(&cur->sem);
+		while (sem_wait(&cur->sem2));
+	}
+	func(ctx);
+
+	for (cur=head; cur; cur=next) {
+		next = cur->next;
+		sem_post(&cur->sem);
+	}
+
+	sa.sa_flags = 0;
+	sa.sa_handler = SIG_IGN;
+	__libc_sigaction(SIGSYNCCALL, &sa, 0);
+
+	__syscall(SYS_rt_sigprocmask, SIG_SETMASK, &oldmask, 0, 8);
+
+	pthread_rwlock_unlock(&lock);
+}
+
+void __synccall_lock()
+{
+	pthread_rwlock_rdlock(&lock);
+}
+
+void __synccall_unlock()
+{
+	pthread_rwlock_unlock(&lock);
+}