[PATCH v3 2/2] Cygwin: signal: Do not handle signal when __SIGFLUSHFAST is sent

[Corinna Vinschen]

Hi Takashi,

do you want to keep it this way, or do you rather want to change
cygwait to use a local timer?


Thanks,
Corinna

On Jan 20 17:52, Takashi Yano wrote:
> The commit a22a0ad7c4f0 was not exactly the correct thing. Even with
> the patch, some hangs still happen. This patch overrides the previous
> commit 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 | 33 +++++++++++++++++++++++++++------
>  1 file changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/winsup/cygwin/sigproc.cc b/winsup/cygwin/sigproc.cc
> index ba7818a68..4dcdd94de 100644
> --- a/winsup/cygwin/sigproc.cc
> +++ b/winsup/cygwin/sigproc.cc
> @@ -751,8 +751,19 @@ 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 ();
> +      if (pack.si.si_signo == __SIGFLUSHFAST)
> +	Sleep (10);
> +      else /* Handle signals */
> +	do
> +	  {
> +	    DWORD rc = WaitForSingleObject (_my_tls.get_signal_arrived (), 10);
> +	    if (rc == WAIT_OBJECT_0)
> +	      {
> +		_my_tls.call_signal_handler ();
> +		continue;
> +	      }
> +	  }
> +	while (false);
>        res = 0;
>      }
>  
> @@ -785,7 +796,20 @@ 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);
> +      if (pack.si.si_signo == __SIGFLUSHFAST)
> +	rc = WaitForSingleObject (pack.wakeup, WSSC);
> +      else /* Handle signals */
> +	do
> +	  {
> +	    HANDLE w[2] = {pack.wakeup, _my_tls.get_signal_arrived ()};
> +	    rc = WaitForMultipleObjects (2, w, FALSE, WSSC);
> +	    if (rc == WAIT_OBJECT_0 + 1) /* signal arrived */
> +	      {
> +		_my_tls.call_signal_handler ();
> +		continue;
> +	      }
> +	  }
> +	while (false);
>        ForceCloseHandle (pack.wakeup);
>      }
>    else
> @@ -806,9 +830,6 @@ 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