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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.
This commit is contained in:
Ken Brown 2020-08-03 09:35:00 -04:00
parent 289af73a89
commit 251624a352
3 changed files with 5 additions and 12 deletions
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9
winsup/cygwin/fhandler.h
View File

@ -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,
};

6
winsup/cygwin/fhandler_fifo.cc
View File

@ -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;

2
winsup/cygwin/select.cc
View File

@ -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)