handle EINTR return code from tcdrain to effectively flush

CHANGELOG.md

@@ -14,6 +14,10 @@ project adheres to [Semantic Versioning](https://semver.org/).
   [#238](https://github.com/serialport/serialport-rs/pull/238)
 
 ### Fixed
+
+* Retry flushing data on `EINTR` up to the ports read/write timeout.
+  [#225](https://github.com/serialport/serialport-rs/pull/225)
+
 ### Removed
 
 

src/posix/tty.rs

@@ -1,7 +1,7 @@
 use std::mem::MaybeUninit;
 use std::os::unix::prelude::*;
 use std::path::Path;
-use std::time::Duration;
+use std::time::{Duration, Instant};
 use std::{io, mem};
 
 use nix::fcntl::{fcntl, OFlag};
@@ -441,8 +441,25 @@ impl io::Write for TTYPort {
     }
 
     fn flush(&mut self) -> io::Result<()> {
-        nix::sys::termios::tcdrain(self.fd)
-            .map_err(|_| io::Error::new(io::ErrorKind::Other, "flush failed"))
+        let timeout = Instant::now() + self.timeout;
+        loop {
+            return match nix::sys::termios::tcdrain(self.fd) {
+                Ok(_) => Ok(()),
+                Err(nix::errno::Errno::EINTR) => {
+                    // Retry flushing. But only up to the ports timeout for not retrying
+                    // indefinitely in case that it gets interrupted again.
+                    if Instant::now() < timeout {
+                        continue;
+                    } else {
+                        Err(io::Error::new(
+                            io::ErrorKind::TimedOut,
+                            "timeout for retrying flush reached",
+                        ))
+                    }
+                }
+                Err(_) => Err(io::Error::new(io::ErrorKind::Other, "flush failed")),
+            };
+        }
     }
 }