[PATCH 10/12] Cygwin: FIFO: allow take_ownership to be interrupted
Ken Brown
kbrown@cornell.edu
Thu Jul 16 16:19:13 GMT 2020
Use cygwait in take_ownership to allow interruption while waiting to
become owner. Return the cygwait return value or a suitable value to
indicate an error.
raw_read now checks the return value and acts accordingly.
---
winsup/cygwin/fhandler.h | 2 +-
winsup/cygwin/fhandler_fifo.cc | 54 ++++++++++++++++++++++++++++++----
winsup/cygwin/select.cc | 11 ++++++-
3 files changed, 59 insertions(+), 8 deletions(-)
diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
index 221c856e6..0e0cfbd71 100644
--- a/winsup/cygwin/fhandler.h
+++ b/winsup/cygwin/fhandler.h
@@ -1489,7 +1489,7 @@ public:
void owner_lock () { shmem->owner_lock (); }
void owner_unlock () { shmem->owner_unlock (); }
- void take_ownership ();
+ DWORD take_ownership ();
void reading_lock () { shmem->reading_lock (); }
void reading_unlock () { shmem->reading_unlock (); }
diff --git a/winsup/cygwin/fhandler_fifo.cc b/winsup/cygwin/fhandler_fifo.cc
index fd1695f40..30486304f 100644
--- a/winsup/cygwin/fhandler_fifo.cc
+++ b/winsup/cygwin/fhandler_fifo.cc
@@ -1175,15 +1175,16 @@ fhandler_fifo::raw_write (const void *ptr, size_t len)
return ret;
}
-/* Called from raw_read and select.cc:peek_fifo. */
-void
+/* Called from raw_read and select.cc:peek_fifo. Return WAIT_OBJECT_0
+ on success. */
+DWORD
fhandler_fifo::take_ownership ()
{
owner_lock ();
if (get_owner () == me)
{
owner_unlock ();
- return;
+ return WAIT_OBJECT_0;
}
set_pending_owner (me);
/* Wake up my fifo_reader_thread. */
@@ -1192,8 +1193,19 @@ fhandler_fifo::take_ownership ()
/* Wake up owner's fifo_reader_thread. */
SetEvent (update_needed_evt);
owner_unlock ();
- /* The reader threads should now do the transfer. */
- WaitForSingleObject (owner_found_evt, INFINITE);
+ /* The reader threads should now do the transfer. */
+ DWORD waitret = cygwait (owner_found_evt, cw_cancel | cw_sig_eintr);
+ owner_lock ();
+ if (waitret == WAIT_OBJECT_0
+ && (get_owner () != me || get_pending_owner ()))
+ {
+ /* Something went wrong. Return WAIT_TIMEOUT, which can't be
+ returned by the above cygwait call. */
+ set_pending_owner (null_fr_id);
+ waitret = WAIT_TIMEOUT;
+ }
+ owner_unlock ();
+ return waitret;
}
void __reg3
@@ -1206,7 +1218,37 @@ fhandler_fifo::raw_read (void *in_ptr, size_t& len)
{
/* No one else can take ownership while we hold the reading_lock. */
reading_lock ();
- take_ownership ();
+ switch (take_ownership ())
+ {
+ case WAIT_OBJECT_0:
+ break;
+ case WAIT_SIGNALED:
+ if (_my_tls.call_signal_handler ())
+ {
+ reading_unlock ();
+ continue;
+ }
+ else
+ {
+ set_errno (EINTR);
+ reading_unlock ();
+ goto errout;
+ }
+ break;
+ case WAIT_CANCELED:
+ reading_unlock ();
+ pthread::static_cancel_self ();
+ break;
+ case WAIT_TIMEOUT:
+ reading_unlock ();
+ debug_printf ("take_ownership returned an unexpected result; retry");
+ continue;
+ default:
+ reading_unlock ();
+ debug_printf ("unknown error while trying to take ownership, %E");
+ goto errout;
+ }
+
/* Poll the connected clients for input. Make two passes. On
the first pass, just try to read from the client from which
we last read successfully. This should minimize
diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
index 80d16f2a7..3f3f33fb5 100644
--- a/winsup/cygwin/select.cc
+++ b/winsup/cygwin/select.cc
@@ -867,7 +867,16 @@ peek_fifo (select_record *s, bool from_select)
}
fh->reading_lock ();
- fh->take_ownership ();
+ if (fh->take_ownership () != WAIT_OBJECT_0)
+ {
+ select_printf ("%s, unable to take ownership", fh->get_name ());
+ fh->reading_unlock ();
+ gotone += s->read_ready = true;
+ if (s->except_selected)
+ gotone += s->except_ready = true;
+ goto out;
+ }
+
fh->fifo_client_lock ();
int nconnected = 0;
for (int i = 0; i < fh->get_nhandlers (); i++)
--
2.27.0
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