[PATCH v3 2/2] Cygwin: pty: Make slave read() thread-safe.

[Takashi Yano via Cygwin-patches]

- Currently slave read() is somehow not thread-safe. This patch
  fixes the issue.
---
 winsup/cygwin/fhandler_tty.cc | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/winsup/cygwin/fhandler_tty.cc b/winsup/cygwin/fhandler_tty.cc
index 06fc19ac2..48b89ae77 100644
--- a/winsup/cygwin/fhandler_tty.cc
+++ b/winsup/cygwin/fhandler_tty.cc
@@ -1241,6 +1241,7 @@ fhandler_pty_slave::read (void *ptr, size_t& len)
        time_to_wait = !vtime ? INFINITE : 100 * vtime;
     }
 
+wait_retry:
   while (len)
     {
       switch (cygwait (input_available_event, time_to_wait))
@@ -1319,6 +1320,11 @@ fhandler_pty_slave::read (void *ptr, size_t& len)
            }
          goto out;
        }
+      if (!IsEventSignalled (input_available_event))
+       { /* Maybe another thread has processed input. */
+         ReleaseMutex (input_mutex);
+         goto wait_retry;
+       }
 
       if (!bytes_available (bytes_in_pipe))
        {
-- 
2.30.0