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Date:	Fri, 29 Apr 2022 00:01:52 +0900
From:	Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
To:	cygwin AT cygwin DOT com
Subject:	Re: GNU make losing jobserver tokens
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On Thu, 28 Apr 2022 16:09:24 +0200
Corinna Vinschen wrote:
> On Apr 28 09:42, Ken Brown wrote:
> > On 4/27/2022 10:13 AM, Takashi Yano wrote:
> > > On Fri, 1 Apr 2022 17:45:51 +0900
> > > Takashi Yano wrote:
> > > > I have tried to reproduce the issue by building OpenJDK
> > > > from source, however, I could not.
> > > > 
> > > > Instead, I encountered another issue.
> > > > 
> > > > Building OpenJDK sometimes (rarely) failed with error such as:
> > > > 
> > > >        0 [sig] make 5484 sig_send: error sending signal 11, pid 5484, pipe handle 0x118, nb 0, packsize 176, Win32 error 0
> > > >   124917 [main] make 5484 sig_send: error sending signal -72, pid 5484, pipe handle 0x118, nb 0, packsize 176, Win32 error 0
> > > > common/modules/GensrcModuleInfo.gmk:77: *** open: /home/yano/jdk/build/windows-x86-server-release/make-support/vardeps/make/common/modules/GensrcModuleInfo.gmk/jdk.accessibility/ALL_MODULES.vardeps: No such file or directory.  Stop.
> > > > make[2]: *** [make/Main.gmk:141: jdk.accessibility-gensrc-moduleinfo] Error 2
> > > > make[2]: *** Waiting for unfinished jobs....
> > > > 
> > > > 
> > > > I looked into this new problem and found that wait_sig() thread
> > > > crashes with segfault. It seems that accessing _main_tls causes
> > > > access violation if a signal is sent just after the process is
> > > > started.
> > > > 
> > > > static void WINAPI
> > > > wait_sig (VOID *)
> > > > {
> > > >    [...]
> > > >        if (!pack.mask)
> > > > 	{
> > > > 	  tl_entry = cygheap->find_tls (_main_tls);
> > > > 	  dummy_mask = _main_tls->sigmask;       // <--- Segfault here
> > > > 	  cygheap->unlock_tls (tl_entry);
> > > > 	  pack.mask = &dummy_mask;
> > > > 	}
> > > > 
> > > > I also found the following patch resolves the issue.
> > > > 
> > > > diff --git a/winsup/cygwin/sigproc.cc b/winsup/cygwin/sigproc.cc
> > > > index 62df96652..3824af199 100644
> > > > --- a/winsup/cygwin/sigproc.cc
> > > > +++ b/winsup/cygwin/sigproc.cc
> > > > @@ -1325,6 +1325,10 @@ wait_sig (VOID *)
> > > >     _sig_tls = &_my_tls;
> > > >     bool sig_held = false;
> > > > +  /* Wait for _main_tls initialization. */
> > > > +  while (!cygwin_finished_initializing)
> > > > +    Sleep (10);
> > > > +
> > > >     sigproc_printf ("entering ReadFile loop, my_readsig %p, my_sendsig %p",
> > > >   		  my_readsig, my_sendsig);
> > > > 
> > > > I guess _main_tls may not be initialized correctly until
> > > > cygwin_finished_initializing is set.
> > > > 
> > > > Any comments would be appreciated.
> > 
> > This seems reasonable to me.

Thanks Ken and Corinna.

> Missed that, sorry. I agree this seems reasonable, but wouldn't it be
> cleaner if we *start* wait_sig only after cygwin_finished_initializing
> is set to true?

I also thought so, however, there is a comment in dcrt0.cc
as follows. So, there seems to be some reason to start
wait_sig before cygwin_finished_initialization.

  /* Initialize signal processing here, early, in the hopes that the creation
     of a thread early in the process will cause more predictability in memory
     layout for the main thread. */
  if (!dynamically_loaded)
    sigproc_init ();


-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

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