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From: Ken Brown <kbrown@sourceware.org> To: cygwin-cvs@sourceware.org Subject: [newlib-cygwin] Cygwin: FIFO: dup/fork/exec: make sure child starts unlocked Date: Fri, 8 May 2020 11:29:37 +0000 (GMT) [thread overview] Message-ID: <20200508112937.4770C396ECFE@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=13c65c43c24015f75b6488dc476b8d7b22c84f18 commit 13c65c43c24015f75b6488dc476b8d7b22c84f18 Author: Ken Brown <kbrown@cornell.edu> Date: Mon May 4 11:36:20 2020 -0400 Cygwin: FIFO: dup/fork/exec: make sure child starts unlocked There can be deadlocks if the child starts with its fifo_client_lock in the locked state. Diff: --- 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
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