Hi Takashi, thank you for the fix! I can confirm that it addresses the problem demonstrated by the reproducer in that MSYS2-runtime ticket.
After noticing that we enumerate all the processes (which is an expensive operation) just to skip all of the non-Cygwin ones anyway, I wonder if it wouldn't be smarter to go through the internal list of cygpids and take it from there, skipping the `SystemProcessInformation` calls altogether. Ciao, Johannes On Sun, 3 Mar 2024, Takashi Yano wrote: > Non-cygwin app may call ReadFile() which makes NtQueryObject() for > ObjectNameInformation block in fhandler_pipe::get_query_hdl_per_process. > Therefore, stop to try to get query_hdl for non-cygwin apps. > > Addresses: https://github.com/msys2/msys2-runtime/issues/202 > > Fixes: b531d6b06eeb ("Cygwin: pipe: Introduce temporary query_hdl.") > Reported-by: Alisa Sireneva, Johannes Schindelin <johannes.schinde...@gmx.de> > Reviewed-by: > Signed-off-by: Takashi Yano <takashi.y...@nifty.ne.jp> > --- > winsup/cygwin/fhandler/pipe.cc | 10 ++++++++++ > winsup/cygwin/release/3.5.2 | 4 ++++ > 2 files changed, 14 insertions(+) > > diff --git a/winsup/cygwin/fhandler/pipe.cc b/winsup/cygwin/fhandler/pipe.cc > index 1a97108b5..95c2f843a 100644 > --- a/winsup/cygwin/fhandler/pipe.cc > +++ b/winsup/cygwin/fhandler/pipe.cc > @@ -1241,6 +1241,16 @@ fhandler_pipe::get_query_hdl_per_process (WCHAR *name, > > for (LONG i = (LONG) n_process - 1; i >= 0; i--) > { > + /* Non-cygwin app may call ReadFile() which makes NtQueryObject() > + for ObjectNameInformation block. Therefore, stop to try to get > + query_hdl for non-cygwin apps. */ > + pid_t cygpid; > + if (!(cygpid = cygwin_pid (proc_pids[i]))) > + continue; > + pinfo p (cygpid); > + if (p && ISSTATE (p, PID_NOTCYGWIN)) > + continue; > + > HANDLE proc = OpenProcess (PROCESS_DUP_HANDLE > | PROCESS_QUERY_INFORMATION, > 0, proc_pids[i]); > diff --git a/winsup/cygwin/release/3.5.2 b/winsup/cygwin/release/3.5.2 > index 7d8df9489..efd30b64a 100644 > --- a/winsup/cygwin/release/3.5.2 > +++ b/winsup/cygwin/release/3.5.2 > @@ -5,3 +5,7 @@ Fixes: > is already unmapped due to race condition. To avoid this issue, > shared console memory will be kept mapped if it belongs to CTTY. > Addresses: https://cygwin.com/pipermail/cygwin/2024-February/255561.html > + > +- Fix a problem that select() call for write-side of a pipe possibly > + hangs with non-cygwin reader. > + Addresses: https://github.com/msys2/msys2-runtime/issues/202 > -- > 2.43.0 > >