[PATCH 07/21] Cygwin: FIFO: dup/fork/exec: make sure child starts unlocked
Ken Brown
kbrown@cornell.edu
Thu May 7 20:21:10 GMT 2020
There can be deadlocks if the child starts with its fifo_client_lock
in the locked state.
---
winsup/cygwin/fhandler_fifo.cc | 31 +++++++++++++++++++++++--------
1 file changed, 23 insertions(+), 8 deletions(-)
diff --git a/winsup/cygwin/fhandler_fifo.cc b/winsup/cygwin/fhandler_fifo.cc
index f61e2fe72..4904a535d 100644
--- a/winsup/cygwin/fhandler_fifo.cc
+++ b/winsup/cygwin/fhandler_fifo.cc
@@ -981,6 +981,9 @@ fhandler_fifo::dup (fhandler_base *child, int flags)
}
if (reader)
{
+ /* Make sure the child starts unlocked. */
+ fhf->fifo_client_unlock ();
+
fifo_client_lock ();
for (i = 0; i < nhandlers; i++)
{
@@ -1025,20 +1028,32 @@ fhandler_fifo::fixup_after_fork (HANDLE parent)
fhandler_base::fixup_after_fork (parent);
fork_fixup (parent, read_ready, "read_ready");
fork_fixup (parent, write_ready, "write_ready");
- fifo_client_lock ();
- for (int i = 0; i < nhandlers; i++)
- fork_fixup (parent, fc_handler[i].h, "fc_handler[].h");
- fifo_client_unlock ();
- if (reader && !listen_client ())
- debug_printf ("failed to start lct, %E");
+ if (reader)
+ {
+ /* Make sure the child starts unlocked. */
+ fifo_client_unlock ();
+
+ fifo_client_lock ();
+ for (int i = 0; i < nhandlers; i++)
+ fork_fixup (parent, fc_handler[i].h, "fc_handler[].h");
+ fifo_client_unlock ();
+ if (!listen_client ())
+ debug_printf ("failed to start lct, %E");
+ }
}
void
fhandler_fifo::fixup_after_exec ()
{
fhandler_base::fixup_after_exec ();
- if (reader && !listen_client ())
- debug_printf ("failed to start lct, %E");
+ if (reader && !close_on_exec ())
+ {
+ /* Make sure the child starts unlocked. */
+ fifo_client_unlock ();
+
+ if (!listen_client ())
+ debug_printf ("failed to start lct, %E");
+ }
}
void
--
2.21.0
More information about the Cygwin-patches
mailing list