After the commit d243e51ef1d3, zsh sometimes hangs at startup. This occurs because SIGCHLD, which should trigger sigsuspend(), is handled in cygwait() that is used to wait for a wakeup event in sig_send(), even when __SIGFLUSHFAST is sent. Despite __SIGFLUSHFAST being required to return before handling the signal, this does not happen. With this patch, if the signal currently being sent is __SIGFLUSHFAST, do not handle the received signal and keep it asserted after the cygwait() for the wakeup event. Apply the same logic to the cygwait() in the retrying loop for WriteFile() as well.
Addresses: https://cygwin.com/pipermail/cygwin/2024-December/256954.html Fixes: d243e51ef1d3 ("Cygwin: signal: Fix deadlock between main thread and sig thread") Reported-by: Daisuke Fujimura <booleanla...@gmail.com> Reviewed-by: Signed-off-by: Takashi Yano <takashi.y...@nifty.ne.jp> --- winsup/cygwin/release/3.5.6 | 5 +++++ winsup/cygwin/sigproc.cc | 20 +++++++++++++++----- 2 files changed, 20 insertions(+), 5 deletions(-) create mode 100644 winsup/cygwin/release/3.5.6 diff --git a/winsup/cygwin/release/3.5.6 b/winsup/cygwin/release/3.5.6 new file mode 100644 index 000000000..643d58e58 --- /dev/null +++ b/winsup/cygwin/release/3.5.6 @@ -0,0 +1,5 @@ +Fixes: +------ + +- Fix zsh hang at startup. + Addresses: https://cygwin.com/pipermail/cygwin/2024-December/256954.html diff --git a/winsup/cygwin/sigproc.cc b/winsup/cygwin/sigproc.cc index ba7818a68..35ec3e70e 100644 --- a/winsup/cygwin/sigproc.cc +++ b/winsup/cygwin/sigproc.cc @@ -751,10 +751,14 @@ sig_send (_pinfo *p, siginfo_t& si, _cygtls *tls) res = WriteFile (sendsig, leader, packsize, &nb, NULL); if (!res || packsize == nb) break; - if (cygwait (NULL, 10, cw_sig_eintr) == WAIT_SIGNALED) + if (cygwait (NULL, 10, cw_sig_eintr) == WAIT_SIGNALED + && pack.si.si_signo != __SIGFLUSHFAST) _my_tls.call_signal_handler (); res = 0; } + /* Re-assert signal_arrived which has been cleared in cygwait(). */ + if (_my_tls.current_sig) + _my_tls.set_signal_arrived (); if (!res) { @@ -785,7 +789,16 @@ sig_send (_pinfo *p, siginfo_t& si, _cygtls *tls) if (wait_for_completion) { sigproc_printf ("Waiting for pack.wakeup %p", pack.wakeup); - rc = cygwait (pack.wakeup, WSSC); + do + { + rc = cygwait (pack.wakeup, WSSC, cw_sig_eintr); + if (rc == WAIT_SIGNALED && pack.si.si_signo != __SIGFLUSHFAST) + _my_tls.call_signal_handler (); + } + while (rc != WAIT_OBJECT_0 && rc != WAIT_TIMEOUT); + /* Re-assert signal_arrived which has been cleared in cygwait(). */ + if (_my_tls.current_sig) + _my_tls.set_signal_arrived (); ForceCloseHandle (pack.wakeup); } else @@ -806,9 +819,6 @@ sig_send (_pinfo *p, siginfo_t& si, _cygtls *tls) rc = -1; } - if (wait_for_completion && si.si_signo != __SIGFLUSHFAST) - _my_tls.call_signal_handler (); - out: if (communing && rc) { -- 2.45.1
