[PATCH 03/12] Cygwin: fhandler_fifo::hit_eof: improve reliability

Ken Brown kbrown@cornell.edu
Thu Jul 16 16:19:06 GMT 2020


Use the writer count introduced in the previous commit to help detect
EOF.  Drop the maybe_eof method, which is no longer needed.
---
 winsup/cygwin/fhandler.h       |  7 +++----
 winsup/cygwin/fhandler_fifo.cc | 26 ++------------------------
 winsup/cygwin/select.cc        |  3 +--
 3 files changed, 6 insertions(+), 30 deletions(-)

diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index f034a110e..b5bfdd0b3 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1392,7 +1392,6 @@ class fhandler_fifo: public fhandler_base
 
   UNICODE_STRING pipe_name;
   WCHAR pipe_name_buf[CYGWIN_FIFO_PIPE_NAME_LEN + 1];
-  bool _maybe_eof;
   fifo_client_handler *fc_handler;     /* Dynamically growing array. */
   int shandlers;                       /* Size (capacity) of the array. */
   int nhandlers;                       /* Number of elements in the array. */
@@ -1473,9 +1472,9 @@ class fhandler_fifo: public fhandler_base
 
 public:
   fhandler_fifo ();
-  bool hit_eof ();
-  bool maybe_eof () const { return _maybe_eof; }
-  void maybe_eof (bool val) { _maybe_eof = val; }
+  /* Called if we appear to be at EOF after polling fc_handlers. */
+  bool hit_eof () const
+  { return !nwriters () && !IsEventSignalled (writer_opening); }
   int get_nhandlers () const { return nhandlers; }
   fifo_client_handler &get_fc_handler (int i) { return fc_handler[i]; }
   PUNICODE_STRING get_pipe_name ();
diff --git a/winsup/cygwin/fhandler_fifo.cc b/winsup/cygwin/fhandler_fifo.cc
index 26b24d019..3685cc0c2 100644
--- a/winsup/cygwin/fhandler_fifo.cc
+++ b/winsup/cygwin/fhandler_fifo.cc
@@ -87,7 +87,7 @@ fhandler_fifo::fhandler_fifo ():
   fhandler_base (),
   read_ready (NULL), write_ready (NULL), writer_opening (NULL),
   owner_needed_evt (NULL), owner_found_evt (NULL), update_needed_evt (NULL),
-  cancel_evt (NULL), thr_sync_evt (NULL), _maybe_eof (false),
+  cancel_evt (NULL), thr_sync_evt (NULL),
   fc_handler (NULL), shandlers (0), nhandlers (0),
   reader (false), writer (false), duplexer (false),
   max_atomic_write (DEFAULT_PIPEBUFSIZE),
@@ -361,8 +361,6 @@ fhandler_fifo::record_connection (fifo_client_handler& fc,
 				  fifo_client_connect_state s)
 {
   fc.state = s;
-  maybe_eof (false);
-  ResetEvent (writer_opening);
   set_pipe_non_blocking (fc.h, true);
 }
 
@@ -1173,25 +1171,6 @@ fhandler_fifo::raw_write (const void *ptr, size_t len)
   return ret;
 }
 
-/* A reader is at EOF if the pipe is empty and no writers are open.
-   hit_eof is called by raw_read and select.cc:peek_fifo if it appears
-   that we are at EOF after polling the fc_handlers.  We recheck this
-   in case a writer opened while we were polling.  */
-bool
-fhandler_fifo::hit_eof ()
-{
-  bool ret = maybe_eof () && !IsEventSignalled (writer_opening);
-  if (ret)
-    {
-      yield ();
-      /* Wait for the reader thread to finish recording any connection. */
-      fifo_client_lock ();
-      fifo_client_unlock ();
-      ret = maybe_eof ();
-    }
-  return ret;
-}
-
 /* Called from raw_read and select.cc:peek_fifo. */
 void
 fhandler_fifo::take_ownership ()
@@ -1261,9 +1240,8 @@ fhandler_fifo::raw_read (void *in_ptr, size_t& len)
 		break;
 	      }
 	  }
-      maybe_eof (!nconnected && !IsEventSignalled (writer_opening));
       fifo_client_unlock ();
-      if (maybe_eof () && hit_eof ())
+      if (!nconnected && hit_eof ())
 	{
 	  reading_unlock ();
 	  len = 0;
diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index 9ae567c38..80d16f2a7 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -883,9 +883,8 @@ peek_fifo (select_record *s, bool from_select)
 		goto out;
 	      }
 	  }
-      fh->maybe_eof (!nconnected);
       fh->fifo_client_unlock ();
-      if (fh->maybe_eof () && fh->hit_eof ())
+      if (!nconnected && fh->hit_eof ())
 	{
 	  select_printf ("read: %s, saw EOF", fh->get_name ());
 	  gotone += s->read_ready = true;
-- 
2.27.0



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