diff --git a/mitogen/master.py b/mitogen/master.py
index 5c1f40e8..e9cad282 100644
--- a/mitogen/master.py
+++ b/mitogen/master.py
@@ -157,14 +157,25 @@ def tty_create_child(*args):
     return pid, master_fd
 
 
-def write_all(fd, s):
+def write_all(fd, s, deadline=None):
+    timeout = None
     written = 0
+
     while written < len(s):
-        rc = os.write(fd, buffer(s, written))
-        if not rc:
-            raise IOError('short write')
-        written += rc
-    return written
+        if deadline is not None:
+            timeout = max(0, deadline - time.time())
+        if timeout == 0:
+            raise mitogen.core.TimeoutError('write timed out')
+
+        _, wfds, _ = select.select([], [fd], [], timeout)
+        if not wfds:
+            continue
+
+        n, disconnected = mitogen.core.io_op(os.write, fd, buffer(s, written))
+        if disconnected:
+            raise mitogen.core.StreamError('EOF on stream during write')
+
+        written += n
 
 
 def iter_read(fd, deadline=None):
diff --git a/tests/data/write_all_consumer.sh b/tests/data/write_all_consumer.sh
new file mode 100755
index 00000000..e6aaaf72
--- /dev/null
+++ b/tests/data/write_all_consumer.sh
@@ -0,0 +1,7 @@
+#!/bin/bash
+# I consume 65535 bytes every 10ms, for testing mitogen.core.write_all()
+
+while :; do
+    read -n 65535
+    sleep 0.01
+done
diff --git a/tests/master_test.py b/tests/master_test.py
index 72318f46..2bea6193 100644
--- a/tests/master_test.py
+++ b/tests/master_test.py
@@ -12,7 +12,9 @@ class IterReadTest(unittest.TestCase):
 
     def make_proc(self):
         args = [testlib.data_path('iter_read_generator.sh')]
-        return subprocess.Popen(args, stdout=subprocess.PIPE)
+        proc = subprocess.Popen(args, stdout=subprocess.PIPE)
+        mitogen.core.set_nonblock(proc.stdout.fileno())
+        return proc
 
     def test_no_deadline(self):
         proc = self.make_proc()
@@ -54,3 +56,43 @@ class IterReadTest(unittest.TestCase):
                 assert 3 < len(got) < 5
         finally:
             proc.terminate()
+
+
+class WriteAllTest(unittest.TestCase):
+    func = staticmethod(mitogen.master.write_all)
+
+    def make_proc(self):
+        args = [testlib.data_path('write_all_consumer.sh')]
+        proc = subprocess.Popen(args, stdin=subprocess.PIPE)
+        mitogen.core.set_nonblock(proc.stdin.fileno())
+        return proc
+
+    ten_ms_chunk = ('x' * 65535)
+
+    def test_no_deadline(self):
+        proc = self.make_proc()
+        try:
+            self.func(proc.stdin.fileno(), self.ten_ms_chunk)
+        finally:
+            proc.terminate()
+
+    def test_deadline_exceeded_before_call(self):
+        proc = self.make_proc()
+        try:
+            self.assertRaises(mitogen.core.TimeoutError, (
+                lambda: self.func(proc.stdin.fileno(), self.ten_ms_chunk, 0)
+            ))
+        finally:
+            proc.terminate()
+
+    def test_deadline_exceeded_during_call(self):
+        proc = self.make_proc()
+        try:
+            deadline = time.time() + 0.1   # 100ms deadline
+            self.assertRaises(mitogen.core.TimeoutError, (
+                lambda: self.func(proc.stdin.fileno(),
+                                  self.ten_ms_chunk * 100,  # 1s of data
+                                  deadline)
+            ))
+        finally:
+            proc.terminate()