Add epoll_pwait2().

I've also added doc comments for everything in <sys/epoll.h>.

I've also broken up the old "smoke" test (which was taking 2s on my
riscv64 qemu) to keep the total runtime for all the tests down to 200ms.

Test: treehugger
Change-Id: Icd939af51886fdf21432653a07373c1a0f26e422
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index f4f9e1b..5791f19 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -322,6 +322,7 @@
 int __epoll_create1:epoll_create1(int)  all
 int epoll_ctl(int, int op, int, struct epoll_event*)  all
 int __epoll_pwait:epoll_pwait(int, struct epoll_event*, int, int, const sigset64_t*, size_t)  all
+int __epoll_pwait2:epoll_pwait2(int, struct epoll_event*, int, const timespec64*, const sigset64_t*, size_t)  all
 
 int __eventfd:eventfd2(unsigned int, int)  all
 
diff --git a/libc/bionic/sys_epoll.cpp b/libc/bionic/sys_epoll.cpp
index cffa173..be97818 100644
--- a/libc/bionic/sys_epoll.cpp
+++ b/libc/bionic/sys_epoll.cpp
@@ -34,6 +34,8 @@
 
 extern "C" int __epoll_create1(int flags);
 extern "C" int __epoll_pwait(int, epoll_event*, int, int, const sigset64_t*, size_t);
+extern "C" int __epoll_pwait2(int, epoll_event*, int, const __kernel_timespec*, const sigset64_t*,
+                              size_t);
 
 int epoll_create(int size) {
   if (size <= 0) {
@@ -56,6 +58,31 @@
   return __epoll_pwait(fd, events, max_events, timeout, ss, sizeof(*ss));
 }
 
+int epoll_pwait2(int fd, epoll_event* events, int max_events, const timespec* timeout,
+                 const sigset_t* ss) {
+  SigSetConverter set{ss};
+  return epoll_pwait2_64(fd, events, max_events, timeout, set.ptr);
+}
+
+int epoll_pwait2_64(int fd, epoll_event* events, int max_events, const timespec* timeout,
+                    const sigset64_t* ss) {
+  // epoll_pwait2() is our first syscall that assumes a 64-bit time_t even for
+  // 32-bit processes, so for ILP32 we need to convert.
+  // TODO: factor this out into a TimeSpecConverter as/when we get more syscalls like this.
+#if __LP64__
+  const __kernel_timespec* kts_ptr = reinterpret_cast<const __kernel_timespec*>(timeout);
+#else
+  __kernel_timespec kts;
+  const __kernel_timespec* kts_ptr = nullptr;
+  if (timeout) {
+    kts.tv_sec = timeout->tv_sec;
+    kts.tv_nsec = timeout->tv_nsec;
+    kts_ptr = &kts;
+  }
+#endif
+  return __epoll_pwait2(fd, events, max_events, kts_ptr, ss, sizeof(*ss));
+}
+
 int epoll_wait(int fd, struct epoll_event* events, int max_events, int timeout) {
   return epoll_pwait64(fd, events, max_events, timeout, nullptr);
 }
diff --git a/libc/include/sys/epoll.h b/libc/include/sys/epoll.h
index 2091b90..2bad655 100644
--- a/libc/include/sys/epoll.h
+++ b/libc/include/sys/epoll.h
@@ -26,8 +26,12 @@
  * SUCH DAMAGE.
  */
 
-#ifndef _SYS_EPOLL_H_
-#define _SYS_EPOLL_H_
+#pragma once
+
+/**
+ * @file sys/epoll.h
+ * @brief I/O event file descriptors.
+ */
 
 #include <sys/cdefs.h>
 #include <sys/types.h>
@@ -37,14 +41,67 @@
 
 __BEGIN_DECLS
 
+/**
+ * [epoll_create(2)](http://man7.org/linux/man-pages/man2/epoll_create.2.html)
+ * creates a new [epoll](http://man7.org/linux/man-pages/man7/epoll.7.html)
+ * file descriptor.
+ *
+ * Returns a new file descriptor on success and returns -1 and sets `errno` on
+ * failure.
+ */
 int epoll_create(int __size);
+
+/**
+ * [epoll_create1(2)](http://man7.org/linux/man-pages/man2/epoll_create1.2.html)
+ * creates a new [epoll](http://man7.org/linux/man-pages/man7/epoll.7.html)
+ * file descriptor with the given flags.
+ *
+ * Returns a new file descriptor on success and returns -1 and sets `errno` on
+ * failure.
+ */
 int epoll_create1(int __flags);
 
+/**
+ * [epoll_ctl(2)](http://man7.org/linux/man-pages/man2/epoll_ctl.2.html)
+ * adds/modifies/removes file descriptors from the given epoll file descriptor.
+ *
+ * Returns 0 on success and returns -1 and sets `errno` on failure.
+ */
 int epoll_ctl(int __epoll_fd, int __op, int __fd, struct epoll_event* __BIONIC_COMPLICATED_NULLNESS __event);
+
+/**
+ * [epoll_wait(2)](http://man7.org/linux/man-pages/man2/epoll_wait.2.html)
+ * waits for an event on the given epoll file descriptor.
+ *
+ * Returns the number of ready file descriptors on success, 0 on timeout,
+ * or -1 and sets `errno` on failure.
+ */
 int epoll_wait(int __epoll_fd, struct epoll_event* _Nonnull __events, int __event_count, int __timeout_ms);
+
+/**
+ * Like epoll_wait() but atomically applying the given signal mask.
+ */
 int epoll_pwait(int __epoll_fd, struct epoll_event* _Nonnull __events, int __event_count, int __timeout_ms, const sigset_t* _Nullable __mask);
+
+/**
+ * Like epoll_pwait() but using a 64-bit signal mask even on 32-bit systems.
+ *
+ * Available since API level 28.
+ */
 int epoll_pwait64(int __epoll_fd, struct epoll_event* _Nonnull __events, int __event_count, int __timeout_ms, const sigset64_t* _Nullable __mask) __INTRODUCED_IN(28);
 
-__END_DECLS
+/**
+ * Like epoll_pwait() but with a `struct timespec` timeout, for nanosecond resolution.
+ *
+ * Available since API level 35.
+ */
+int epoll_pwait2(int __epoll_fd, struct epoll_event* _Nonnull __events, int __event_count, const struct timespec* _Nullable __timeout, const sigset_t* _Nullable __mask) __INTRODUCED_IN(35);
 
-#endif
+/**
+ * Like epoll_pwait2() but using a 64-bit signal mask even on 32-bit systems.
+ *
+ * Available since API level 35.
+ */
+int epoll_pwait2_64(int __epoll_fd, struct epoll_event* _Nonnull __events, int __event_count, const struct timespec* _Nullable __timeout, const sigset64_t* _Nullable __mask) __INTRODUCED_IN(35);
+
+__END_DECLS
diff --git a/libc/libc.map.txt b/libc/libc.map.txt
index e90618d..75b3d86 100644
--- a/libc/libc.map.txt
+++ b/libc/libc.map.txt
@@ -1586,6 +1586,8 @@
 
 LIBC_V { # introduced=VanillaIceCream
   global:
+    epoll_pwait2;
+    epoll_pwait2_64;
     localtime_rz;
     mbsrtowcs_l;
     mktime_z;