[newlib-cygwin] Cygwin: FIFO: don't read from pipes that are closing
Ken Brown
kbrown@sourceware.org
Tue Aug 4 15:29:36 GMT 2020
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=251624a3529c3d0d3d9cdb5fbaf4c3e9b079c894
commit 251624a3529c3d0d3d9cdb5fbaf4c3e9b079c894
Author: Ken Brown <kbrown@cornell.edu>
Date: Mon Aug 3 09:35:00 2020 -0400
Cygwin: FIFO: don't read from pipes that are closing
Don't try to read from fifo_client_handlers that are in the fc_closing
state. Experiments have shown that this always yields
STATUS_PIPE_BROKEN, so it just wastes a Windows system call.
Re-order the values in enum fifo_client_connect_state to reflect the
new status of fc_closing.
Diff:
---
winsup/cygwin/fhandler.h | 9 +--------
winsup/cygwin/fhandler_fifo.cc | 6 +++---
winsup/cygwin/select.cc | 2 +-
3 files changed, 5 insertions(+), 12 deletions(-)
diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index f64eabda4..40e201b0f 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1276,20 +1276,13 @@ public:
#define CYGWIN_FIFO_PIPE_NAME_LEN 47
-/* We view the fc_closing state as borderline between open and closed
- for a writer at the other end of a fifo_client_handler.
-
- We still attempt to read from the writer when the handler is in
- this state, and we don't declare a reader to be at EOF if there's a
- handler in this state. But the existence of a handler in this
- state is not sufficient to unblock a reader trying to open. */
enum fifo_client_connect_state
{
fc_unknown,
fc_error,
fc_disconnected,
- fc_listening,
fc_closing,
+ fc_listening,
fc_connected,
fc_input_avail,
};
diff --git a/winsup/cygwin/fhandler_fifo.cc b/winsup/cygwin/fhandler_fifo.cc
index c816c692a..1e1140f53 100644
--- a/winsup/cygwin/fhandler_fifo.cc
+++ b/winsup/cygwin/fhandler_fifo.cc
@@ -365,7 +365,7 @@ fhandler_fifo::cleanup_handlers ()
while (i < nhandlers)
{
- if (fc_handler[i].get_state () < fc_closing)
+ if (fc_handler[i].get_state () < fc_connected)
delete_client_handler (i);
else
i++;
@@ -1280,7 +1280,7 @@ fhandler_fifo::raw_read (void *in_ptr, size_t& len)
for (j = 0; j < nhandlers; j++)
if (fc_handler[j].last_read)
break;
- if (j < nhandlers && fc_handler[j].get_state () >= fc_closing)
+ if (j < nhandlers && fc_handler[j].get_state () >= fc_connected)
{
NTSTATUS status;
IO_STATUS_BLOCK io;
@@ -1315,7 +1315,7 @@ fhandler_fifo::raw_read (void *in_ptr, size_t& len)
/* Second pass. */
for (int i = 0; i < nhandlers; i++)
- if (fc_handler[i].get_state () >= fc_closing)
+ if (fc_handler[i].get_state () >= fc_connected)
{
NTSTATUS status;
IO_STATUS_BLOCK io;
diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index 0c94f6c45..9ee305f64 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -878,7 +878,7 @@ peek_fifo (select_record *s, bool from_select)
{
fifo_client_handler &fc = fh->get_fc_handler (i);
fc.query_and_set_state ();
- if (fc.get_state () >= fc_closing)
+ if (fc.get_state () >= fc_connected)
{
nconnected++;
if (fc.get_state () == fc_input_avail)
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