Add a "fork" of musl as //fusl.

fusl/src/time/timer_create.c

+#include <time.h>
+#include <setjmp.h>
+#include "pthread_impl.h"
+
+struct ksigevent {
+        union sigval sigev_value;
+        int sigev_signo;
+        int sigev_notify;
+        int sigev_tid;
+};
+
+struct start_args {
+        pthread_barrier_t b;
+        struct sigevent *sev;
+};
+
+static void dummy_1(pthread_t self)
+{
+}
+weak_alias(dummy_1, __pthread_tsd_run_dtors);
+
+void __reset_tls();
+
+static void cleanup_fromsig(void *p)
+{
+        pthread_t self = __pthread_self();
+        __pthread_tsd_run_dtors(self);
+        self->cancel = 0;
+        self->cancelbuf = 0;
+        self->canceldisable = 0;
+        self->cancelasync = 0;
+        self->unblock_cancel = 0;
+        __reset_tls();
+        longjmp(p, 1);
+}
+
+static void timer_handler(int sig, siginfo_t *si, void *ctx)
+{
+        pthread_t self = __pthread_self();
+        jmp_buf jb;
+        void (*notify)(union sigval) = (void (*)(union sigval))self->start;
+        union sigval val = { .sival_ptr = self->start_arg };
+
+        if (!setjmp(jb) && si->si_code == SI_TIMER) {
+                pthread_cleanup_push(cleanup_fromsig, jb);
+                notify(val);
+                pthread_cleanup_pop(1);
+        }
+}
+
+static void install_handler()
+{
+        struct sigaction sa = {
+                .sa_sigaction = timer_handler,
+                .sa_flags = SA_SIGINFO | SA_RESTART
+        };
+        __libc_sigaction(SIGTIMER, &sa, 0);
+}
+
+static void *start(void *arg)
+{
+        pthread_t self = __pthread_self();
+        struct start_args *args = arg;
+        int id;
+
+        /* Reuse no-longer-needed thread structure fields to avoid
+         * needing the timer address in the signal handler. */
+        self->start = (void *(*)(void *))args->sev->sigev_notify_function;
+        self->start_arg = args->sev->sigev_value.sival_ptr;
+
+        pthread_barrier_wait(&args->b);
+        if ((id = self->timer_id) >= 0) {
+                __syscall(SYS_rt_sigprocmask, SIG_UNBLOCK,
+                        SIGTIMER_SET, 0, _NSIG/8);
+                __wait(&self->timer_id, 0, id, 1);
+                __syscall(SYS_timer_delete, id);
+        }
+        return 0;
+}
+
+int timer_create(clockid_t clk, struct sigevent *restrict evp, timer_t *restrict res)
+{
+        static pthread_once_t once = PTHREAD_ONCE_INIT;
+        pthread_t td;
+        pthread_attr_t attr;
+        int r;
+        struct start_args args;
+        struct ksigevent ksev, *ksevp=0;
+        int timerid;
+        sigset_t set;
+
+        switch (evp ? evp->sigev_notify : SIGEV_SIGNAL) {
+        case SIGEV_NONE:
+        case SIGEV_SIGNAL:
+                if (evp) {
+                        ksev.sigev_value = evp->sigev_value;
+                        ksev.sigev_signo = evp->sigev_signo;
+                        ksev.sigev_notify = evp->sigev_notify;
+                        ksev.sigev_tid = 0;
+                        ksevp = &ksev;
+                }
+                if (syscall(SYS_timer_create, clk, ksevp, &timerid) < 0)
+                        return -1;
+                *res = (void *)(intptr_t)timerid;
+                break;
+        case SIGEV_THREAD:
+                pthread_once(&once, install_handler);
+                if (evp->sigev_notify_attributes)
+                        attr = *evp->sigev_notify_attributes;
+                else
+                        pthread_attr_init(&attr);
+                pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+                pthread_barrier_init(&args.b, 0, 2);
+                args.sev = evp;
+
+                __block_app_sigs(&set);
+                r = pthread_create(&td, &attr, start, &args);
+                __restore_sigs(&set);
+                if (r) {
+                        errno = r;
+                        return -1;
+                }
+
+                ksev.sigev_value.sival_ptr = 0;
+                ksev.sigev_signo = SIGTIMER;
+                ksev.sigev_notify = 4; /* SIGEV_THREAD_ID */
+                ksev.sigev_tid = td->tid;
+                if (syscall(SYS_timer_create, clk, &ksev, &timerid) < 0)
+                        timerid = -1;
+                td->timer_id = timerid;
+                pthread_barrier_wait(&args.b);
+                if (timerid < 0) return -1;
+                *res = (void *)(INTPTR_MIN | (uintptr_t)td>>1);
+                break;
+        default:
+                errno = EINVAL;
+                return -1;
+        }
+
+        return 0;
+}