DMARC-Filter: OpenDMARC Filter v1.4.2 delorie.com 56HFjE651104402
Authentication-Results: delorie.com; dmarc=pass (p=none dis=none) header.from=cygwin.com
Authentication-Results: delorie.com; spf=pass smtp.mailfrom=cygwin.com
DKIM-Filter: OpenDKIM Filter v2.11.0 delorie.com 56HFjE651104402
Authentication-Results: delorie.com;
	dkim=pass (1024-bit key, unprotected) header.d=cygwin.com header.i=@cygwin.com header.a=rsa-sha256 header.s=default header.b=KaR9iAMQ
X-Recipient: archive-cygwin AT delorie DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2FE38385EC26
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1752767113;
	bh=8p8Gc8vXUBOZreDLyNStoSr76ZXab7sYxYF7sztALro=;
	h=Date:To:Subject:In-Reply-To:References:List-Id:List-Unsubscribe:
	 List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:
	 From;
	b=KaR9iAMQ3fXjhljBSn04BhqLV1eco/n534pyWupbzKkNiowvVftSQFOnz+DdbJcdp
	 ZznJNoL7/UQRV0HC9M/S931pfwB/LE4zogcyVRDLF1M1YUoILLkP7NCyZstvZg9ko3
	 zvJ2CWseKJGpbNmGfbBhSywhNU3WQZzpwQyrUNg4=
X-Original-To: cygwin AT cygwin DOT com
Delivered-To: cygwin AT cygwin DOT com
DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 33C4F385DDFD
ARC-Filter: OpenARC Filter v1.0.0 sourceware.org 33C4F385DDFD
ARC-Seal: i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1752767089; cv=none;
 b=TqAyCwQB4/OiAdyvcQbTNVyAGGp8CDW0UbnHxX1vCs8ZMmyTSt7fma1kJn3wYs68zyqHqT9pZPyPTT9Y6VLUy1vq0mYHckKEgWjw3b1LZAukTorR8ftgcQ3PxB7P1K/69qFWO5jb7bMVPUypbUAXnNWdSjkOjL06L9O9Ou77y4g=
ARC-Message-Signature: i=1; a=rsa-sha256; d=sourceware.org; s=key;
 t=1752767089; c=relaxed/simple;
 bh=O760X966cjybT2w/zkYkhYIr4DiezjhN/uLe1tuQv2Q=;
 h=Date:From:To:Subject:Message-Id:Mime-Version:DKIM-Signature;
 b=qKJlBwk1ezCmMk8wzAW04r2RT5hREzJzd+deLaBELuZJ/N6q5YBI9lrwTLn5A700CrzQkLkAw2V3oVWAtpieuWD/ZynWHgvA12FBlTd5eFLL/A/pZ/bV6Yd5uPZv3RMip5XGXPYvL6UxWCvxgy31zFYQEexzFowGH/D5llM4654=
ARC-Authentication-Results: i=1; server2.sourceware.org
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 33C4F385DDFD
Date: Fri, 18 Jul 2025 00:44:46 +0900
To: cygwin AT cygwin DOT com
Subject: Re: Calling system() in multi-threads.
Message-Id: <20250718004446.9ce9f7f208566ded1a676fd5@nifty.ne.jp>
In-Reply-To: <aHkUldQHKjA-lZrw@calimero.vinschen.de>
References: <20250617215411 DOT ebf69d1c18b55191a1b76c01 AT nifty DOT ne DOT jp>
 <eb7786ee-dc7a-4689-9d17-b842e581d7c7 AT maxrnd DOT com>
 <20250618203127 DOT 71ac180de11230a9a6055185 AT nifty DOT ne DOT jp>
 <20250716235236 DOT 96055ec145d9a0528b50c357 AT nifty DOT ne DOT jp>
 <aHfHCqD2xZcdyu7u AT calimero DOT vinschen DOT de>
 <20250717231421 DOT 56b54f7e96266311101d4c08 AT nifty DOT ne DOT jp>
 <aHkUldQHKjA-lZrw AT calimero DOT vinschen DOT de>
X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.30; i686-pc-mingw32)
Mime-Version: 1.0
X-BeenThere: cygwin AT cygwin DOT com
X-Mailman-Version: 2.1.30
Precedence: list
List-Id: General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe: <https://cygwin.com/mailman/options/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive: <https://cygwin.com/pipermail/cygwin/>
List-Post: <mailto:cygwin AT cygwin DOT com>
List-Help: <mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe: <https://cygwin.com/mailman/listinfo/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
From: Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To: Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
Content-Type: text/plain; charset="utf-8"
Errors-To: cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com
Sender: "Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>
Content-Transfer-Encoding: 8bit
X-MIME-Autoconverted: from base64 to 8bit by delorie.com id 56HFjE651104402

On Thu, 17 Jul 2025 17:19:49 +0200
Corinna Vinschen wrote:
> On Jul 17 23:14, Takashi Yano via Cygwin wrote:
> > Hi Corinna,
> > 
> > On Wed, 16 Jul 2025 17:36:42 +0200
> > Corinna Vinschen wrote:
> > > On Jul 16 23:52, Takashi Yano via Cygwin wrote:
> > > > Do you have any idea?
> > > 
> > > Locking would be super-simple.
> > > 
> > > But theoretically it should be possible to use a local child_info_spawn
> > > variable at this point.  The ch_spawn child_info_spawn instance is not
> > > copied to the child anyway, so that should be safe.  The same goes for
> > > posix_spawn() then, btw.
> > > 
> > > I checked the sources and I don't see any dependency to ch_spawn
> > > from a spawning process, in contrast to an exec'ing process.  That
> > > doesn't mean there is none, just that I didn't find any.
> > 
> > Thanks!
> > As a starting point, I tried tntroducing locking. It almost works
> > as expected, however, sometimes my STC in my first report is hangs
> > if N is large e.g. 100. The patch is as attached.
> > 
> > What am I missing?
> 
> I don't know.  You're perhaps not releasing the lock in all cases.
> But I would have to debug this just like you ¯\_(ツ)_/¯
> 
> Out of curiosity, did you try using a locale child_info_spawn instance
> instead?  That would be a rather nice solution, but I'm pretty sure
> there's some other problem lurking in the dark...

I'm not sure what to do with local child_info_spawn.
Some of other modules refer to ch_spawn, such as exception.cc and
pinfo.cc. Also, has_execed* uses ch_spawn. What should we do for that?

I've just tried simply the following patch, however, this also hangs
with my STC.

diff --git a/winsup/cygwin/spawn.cc b/winsup/cygwin/spawn.cc
index cb58b6eed..56fca6e45 100644
--- a/winsup/cygwin/spawn.cc
+++ b/winsup/cygwin/spawn.cc
@@ -944,6 +944,7 @@ spawnve (int mode, const char *path, const char *const *argv,
   int ret;
 
   syscall_printf ("spawnve (%s, %s, %p)", path, argv[0], envp);
+  child_info_spawn ch_spawn_local;
 
   if (!envp)
     envp = empty_env;
@@ -951,7 +952,7 @@ spawnve (int mode, const char *path, const char *const *argv,
   switch (_P_MODE (mode))
     {
     case _P_OVERLAY:
-      ch_spawn.worker (path, argv, envp, mode);
+      ch_spawn_local.worker (path, argv, envp, mode);
       /* Errno should be set by worker.  */
       ret = -1;
       break;
@@ -961,7 +962,7 @@ spawnve (int mode, const char *path, const char *const *argv,
     case _P_WAIT:
     case _P_DETACH:
     case _P_SYSTEM:
-      ret = ch_spawn.worker (path, argv, envp, mode);
+      ret = ch_spawn_local.worker (path, argv, envp, mode);
       break;
     default:
       set_errno (EINVAL);

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

-- 
Problem reports:      https://cygwin.com/problems.html
FAQ:                  https://cygwin.com/faq/
Documentation:        https://cygwin.com/docs.html
Unsubscribe info:     https://cygwin.com/ml/#unsubscribe-simple