diff --git a/libc/bionic/posix_timers.cpp b/libc/bionic/posix_timers.cpp
new file mode 100644
index 0000000..ffe213c
--- /dev/null
+++ b/libc/bionic/posix_timers.cpp
@@ -0,0 +1,221 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "pthread_internal.h"
+#include "private/bionic_futex.h"
+#include "private/bionic_pthread.h"
+#include "private/kernel_sigset_t.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+// System calls.
+extern "C" int __rt_sigtimedwait(const sigset_t*, siginfo_t*, const struct timespec*, size_t);
+extern "C" int __timer_create(clockid_t, sigevent*, __kernel_timer_t*);
+extern "C" int __timer_delete(__kernel_timer_t);
+extern "C" int __timer_getoverrun(__kernel_timer_t);
+extern "C" int __timer_gettime(__kernel_timer_t, itimerspec*);
+extern "C" int __timer_settime(__kernel_timer_t, int, const itimerspec*, itimerspec*);
+
+// Most POSIX timers are handled directly by the kernel. We translate SIGEV_THREAD timers
+// into SIGEV_THREAD_ID timers so the kernel handles all the time-related stuff and we just
+// need to worry about running user code on a thread.
+
+// We can't use SIGALRM because too many other C library functions throw that around, and since
+// they don't send to a specific thread, all threads are eligible to handle the signal and we can
+// end up with one of our POSIX timer threads handling it (meaning that the intended recipient
+// doesn't). glibc uses SIGRTMIN for its POSIX timer implementation, so in the absence of any
+// reason to use anything else, we use that too.
+static const int TIMER_SIGNAL = SIGRTMIN;
+
+struct PosixTimer {
+  __kernel_timer_t kernel_timer_id;
+
+  int sigev_notify;
+
+  // These fields are only needed for a SIGEV_THREAD timer.
+  pthread_t callback_thread;
+  void (*callback)(sigval_t);
+  sigval_t callback_argument;
+  volatile int exiting;
+};
+
+static __kernel_timer_t to_kernel_timer_id(timer_t timer) {
+  return reinterpret_cast<PosixTimer*>(timer)->kernel_timer_id;
+}
+
+static void* __timer_thread_start(void* arg) {
+  PosixTimer* timer = reinterpret_cast<PosixTimer*>(arg);
+
+  kernel_sigset_t sigset;
+  sigaddset(sigset.get(), TIMER_SIGNAL);
+
+  while (true) {
+    // Wait for a signal...
+    siginfo_t si;
+    memset(&si, 0, sizeof(si));
+    int rc = __rt_sigtimedwait(sigset.get(), &si, NULL, sizeof(sigset));
+    if (rc == -1) {
+      continue;
+    }
+
+    if (si.si_code == SI_TIMER) {
+      // This signal was sent because a timer fired, so call the callback.
+      timer->callback(timer->callback_argument);
+    } else if (si.si_code == SI_TKILL) {
+      // This signal was sent because someone wants us to exit.
+      timer->exiting = 1;
+      __futex_wake(&timer->exiting, INT32_MAX);
+      return NULL;
+    }
+  }
+}
+
+static void __timer_thread_stop(PosixTimer* timer) {
+  pthread_kill(timer->callback_thread, TIMER_SIGNAL);
+
+  // We can't pthread_join because POSIX says "the threads created in response to a timer
+  // expiration are created detached, or in an unspecified way if the thread attribute's
+  // detachstate is PTHREAD_CREATE_JOINABLE".
+  while (timer->exiting == 0) {
+    __futex_wait(&timer->exiting, 0, NULL);
+  }
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_create.html
+int timer_create(clockid_t clock_id, sigevent* evp, timer_t* timer_id) {
+  PosixTimer* new_timer = reinterpret_cast<PosixTimer*>(malloc(sizeof(PosixTimer)));
+  if (new_timer == NULL) {
+    return -1;
+  }
+
+  new_timer->sigev_notify = (evp == NULL) ? SIGEV_SIGNAL : evp->sigev_notify;
+
+  // If not a SIGEV_THREAD timer, the kernel can handle it without our help.
+  if (new_timer->sigev_notify != SIGEV_THREAD) {
+    if (__timer_create(clock_id, evp, &new_timer->kernel_timer_id) == -1) {
+      free(new_timer);
+      return -1;
+    }
+
+    *timer_id = new_timer;
+    return 0;
+  }
+
+  // Otherwise, this must be SIGEV_THREAD timer...
+  new_timer->callback = evp->sigev_notify_function;
+  new_timer->callback_argument = evp->sigev_value;
+  new_timer->exiting = 0;
+
+  // Check arguments that the kernel doesn't care about but we do.
+  if (new_timer->callback == NULL) {
+    free(new_timer);
+    errno = EINVAL;
+    return -1;
+  }
+
+  // Create this timer's thread.
+  pthread_attr_t thread_attributes;
+  if (evp->sigev_notify_attributes == NULL) {
+    pthread_attr_init(&thread_attributes);
+  } else {
+    thread_attributes = *reinterpret_cast<pthread_attr_t*>(evp->sigev_notify_attributes);
+  }
+  pthread_attr_setdetachstate(&thread_attributes, PTHREAD_CREATE_DETACHED);
+
+  // We start the thread with TIMER_SIGNAL blocked by blocking the signal here and letting it
+  // inherit. If it tried to block the signal itself, there would be a race.
+  kernel_sigset_t sigset;
+  sigaddset(sigset.get(), TIMER_SIGNAL);
+  kernel_sigset_t old_sigset;
+  pthread_sigmask(SIG_BLOCK, sigset.get(), old_sigset.get());
+
+  int rc = pthread_create(&new_timer->callback_thread, &thread_attributes, __timer_thread_start, new_timer);
+
+  pthread_sigmask(SIG_SETMASK, old_sigset.get(), NULL);
+
+  if (rc != 0) {
+    free(new_timer);
+    errno = rc;
+    return -1;
+  }
+
+  sigevent se = *evp;
+  se.sigev_signo = TIMER_SIGNAL;
+  se.sigev_notify = SIGEV_THREAD_ID;
+  se.sigev_notify_thread_id = __pthread_gettid(new_timer->callback_thread);
+  if (__timer_create(clock_id, &se, &new_timer->kernel_timer_id) == -1) {
+    __timer_thread_stop(new_timer);
+    free(new_timer);
+    return -1;
+  }
+
+  // Give the thread a meaningful name.
+  // It can't do this itself because the kernel timer isn't created until after it's running.
+  char name[32];
+  snprintf(name, sizeof(name), "POSIX interval timer %d", to_kernel_timer_id(new_timer));
+  pthread_setname_np(new_timer->callback_thread, name);
+
+  *timer_id = new_timer;
+  return 0;
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_delete.html
+int timer_delete(timer_t id) {
+  int rc = __timer_delete(to_kernel_timer_id(id));
+  if (rc == -1) {
+    return -1;
+  }
+
+  PosixTimer* timer = reinterpret_cast<PosixTimer*>(id);
+
+  // Make sure the timer's thread has exited before we free the timer data.
+  if (timer->sigev_notify == SIGEV_THREAD) {
+    __timer_thread_stop(timer);
+  }
+
+  free(timer);
+
+  return 0;
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
+int timer_gettime(timer_t id, itimerspec* ts) {
+  return __timer_gettime(to_kernel_timer_id(id), ts);
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
+int timer_settime(timer_t id, int flags, const itimerspec* ts, itimerspec* ots) {
+  return __timer_settime(to_kernel_timer_id(id), flags, ts, ots);
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
+int timer_getoverrun(timer_t id) {
+  return __timer_getoverrun(to_kernel_timer_id(id));
+}