[PATCH v5 3/3] Cygwin: signal: Do not handle signal when __SIGFLUSHFAST is sent

[Takashi Yano]

The commit a22a0ad7c4f0 was not exactly the correct thing. Even with
the patch, some hangs still happen. This patch overrides the previous
commit togerther with the patch making cygwait() reentrant to fix these
hangs.

Addresses: https://cygwin.com/pipermail/cygwin/2024-December/256954.html
Addresses: https://cygwin.com/pipermail/cygwin/2024-December/256987.html
Fixes: d243e51ef1d3 ("Cygwin: signal: Fix deadlock between main thread and sig thread")
Fixes: a22a0ad7c4f0 ("Cygwin: signal: Do not handle signal when __SIGFLUSHFAST is sent")
Reported-by: Daisuke Fujimura <booleanlabel@gmail.com>
Reported-by: Jeremy Drake <cygwin@jdrake.com>
Reviewed-by:
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
 winsup/cygwin/sigproc.cc | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/winsup/cygwin/sigproc.cc b/winsup/cygwin/sigproc.cc
index ba7818a68..408784e5d 100644
--- a/winsup/cygwin/sigproc.cc
+++ b/winsup/cygwin/sigproc.cc
@@ -742,6 +742,12 @@ sig_send (_pinfo *p, siginfo_t& si, _cygtls *tls)
       memcpy (p, si._si_commune._si_str, n); p += n;
     }
 
+  unsigned cw_mask;
+  if (pack.si.si_signo == __SIGFLUSHFAST)
+    cw_mask = 0;
+  else
+    cw_mask = cw_sig_restart;
+
   DWORD nb;
   BOOL res;
   /* Try multiple times to send if packsize != nb since that probably
@@ -751,8 +757,7 @@ 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)
-	_my_tls.call_signal_handler ();
+      cygwait (NULL, 10, cw_mask);
       res = 0;
     }
 
@@ -785,7 +790,7 @@ 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);
+      rc = cygwait (pack.wakeup, WSSC, cw_mask);
       ForceCloseHandle (pack.wakeup);
     }
   else
@@ -806,9 +811,6 @@ 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