[PATCH v4] Cygwin: signal: Optimize the priority of the sig thread

[Takashi Yano]

On Tue, 3 Dec 2024 15:31:01 +0100
Corinna Vinschen wrote:
> On Dec  3 23:01, Takashi Yano wrote:
> > Previously, the sig thread ran in THREAD_PRIORITY_HIGHEST priority.
> > This causes a critical delay in the signal handling in the main
> > thread if too many signals are received rapidly and the CPU is very
> > busy. In this case, most of the CPU time is allocated to the sig
> > thread, so the main thread cannot have a chance of handling signals.
> > With this patch, to avoid such a situation, the priority of the sig
> > thread is set to THREAD_PRIORITY_NORMAL priority.
> > 
> > Addresses: https://cygwin.com/pipermail/cygwin/2024-November/256744.html
> > Fixes: 53ad6f1394aa ("(cygthread::cygthread): Use three only arguments for detached threads, and start the thread via QueueUserAPC/async_create.")
> > Reported-by: Christian Franke <Christian.Franke@t-online.de>
> > Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
> > Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
> > ---
> >  winsup/cygwin/sigproc.cc | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/winsup/cygwin/sigproc.cc b/winsup/cygwin/sigproc.cc
> > index 730259484..4c557f048 100644
> > --- a/winsup/cygwin/sigproc.cc
> > +++ b/winsup/cygwin/sigproc.cc
> > @@ -1333,6 +1333,7 @@ wait_sig (VOID *)
> >  
> >    hntdll = GetModuleHandle ("ntdll.dll");
> >  
> > +  SetThreadPriority (GetCurrentThread (), THREAD_PRIORITY_NORMAL);
> >    for (;;)
> >      {
> >        DWORD nb;
> > -- 
> > 2.45.1
> 
> Yep, please push.  This is the one you can eventually push to
> the 3.5 branch.
> 
> For 3.6 I suggest that you or I'll submit a patch removing this line
> again, in favor of dropping the line in cygthread::async_create
> setting the prio to HIGHEST.  But only after the threasd series is
> complete, ok?

I see.

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>