diff options
author | Christopher Faylor <me@cgf.cx> | 2012-12-28 22:06:17 +0400 |
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committer | Christopher Faylor <me@cgf.cx> | 2012-12-28 22:06:17 +0400 |
commit | 871d0724fa3251afb026608af733d6eea4dce8fd (patch) | |
tree | 4a098fc2495b314174d0bd627861d14a0228146d /winsup/cygwin/DevNotes | |
parent | 81f18683364bdd83dcf74f57dee24599d86ae4f3 (diff) |
* DevNotes: Add entry cgf-000019.
* dcrt0.cc (do_exit): Just set exit_state to ES_EVENTS_TERMINATE and nuke call
to events_terminate which just set a superfluous flag.
* sigproc.cc (signal_exit_code): New variable.
(setup_signal_exit): Define new function.
(_cygtls::signal_exit): Remove accommodations for closing the signal pipe
handle.
(exit_thread): Just sleep if we're exiting.
(wait_sig): If signal_exit_code is set, just handle bookkeeping signals and
exit ReadFile loop if there is nothing more to process. Call signal_exit at
end if signal_exit_code is non-zero.
* sigproc.h (setup_signal_exit): Declare new function.
* exceptions.cc (sigpacket::process): Use setup_signal_exit to control exiting
due to a signal.
(exception::handle): Ditto. Query exit_state rather than defunct exit_already
to determine if we are exiting.
* globals.cc (ES_SIGNAL_EXIT): New enum.
* sync.h (lock_process::release): New function for explicitly unlocking muto.
(lock_process::~lock_process): Use release method.
Diffstat (limited to 'winsup/cygwin/DevNotes')
-rw-r--r-- | winsup/cygwin/DevNotes | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/winsup/cygwin/DevNotes b/winsup/cygwin/DevNotes index 04abd99cc..01293bc50 100644 --- a/winsup/cygwin/DevNotes +++ b/winsup/cygwin/DevNotes @@ -1,3 +1,32 @@ +2012-12-28 cgf-000019 + +(I forgot to mention that cgf-000018 was reverted. Although I never saw +a hang from this, I couldn't convince myself that one wasn't possible.) + +This fix attempts to correct a deadlock where, when a true Windows +signal arrives, Windows creates a thread which "does stuff" and attempts +to exit. In the process of exiting Cygwin grabs the process lock. If +the signal thread has seen the signal and wants to exit, it can't +because the newly-created thread now holds it. But, since the new +thread is relying on the signal thread to release its process lock, +it exits and the process lock is never released. + +To fix this, I removed calls to _cygtls::signal_exit in favor of +flagging that we were exiting by setting signal_exit_code (almost forgot +to mark that NO_COPY: that would have been fun). The new function +setup_signal_exit() now handles setting things up so that ReadFile loop +in wait_sig will do the right thing when it terminates. This function +may just Sleep indefinitely if a signal is being sent from a thread +other than the signal thread. wait_sig() was changed so that it will +essentially drop into asychronous-read-mode when a signal which exits +has been detected. The ReadFile loop is exited when we know that the +process is supposed to be exiting and there is nothing else in the +signal queue. + +Although I never actually saw this happen, exit_thread() was also +changed to release the process lock and just sleep indefintely if it is +detected that we are exiting. + 2012-12-21 cgf-000018 Re: cgf-000017 |