Work around 32 bits epoll_wait() bug (#1349)

A bug in kernels < 2.6.37 makes timeouts larger than LONG_MAX /
CONFIG_HZ (approx. 30 minutes with CONFIG_HZ=1200) effectively
infinite on 32 bits architectures. The magic number is the same
constant used by libuv, see commit libuv/libuv@d1b5008e76.

src/sys/unix/selector/epoll.rs

@@ -46,8 +46,16 @@ impl Selector {
     }
 
     pub fn select(&self, events: &mut Events, timeout: Option<Duration>) -> io::Result<()> {
+        // A bug in kernels < 2.6.37 makes timeouts larger than LONG_MAX / CONFIG_HZ
+        // (approx. 30 minutes with CONFIG_HZ=1200) effectively infinite on 32 bits
+        // architectures. The magic number is the same constant used by libuv.
+        #[cfg(target_pointer_width = "32")]
+        const MAX_SAFE_TIMEOUT: u128 = 1789569;
+        #[cfg(not(target_pointer_width = "32"))]
+        const MAX_SAFE_TIMEOUT: u128 = libc::c_int::max_value() as u128;
+
         let timeout = timeout
-            .map(|to| cmp::min(to.as_millis(), libc::c_int::max_value() as u128) as libc::c_int)
+            .map(|to| cmp::min(to.as_millis(), MAX_SAFE_TIMEOUT) as libc::c_int)
             .unwrap_or(-1);
 
         events.clear();