[newlib-cygwin] Cygwin: dsp: Fix hang on close() if another thread calls write().

[Takashi Yano <tyan0@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=bf915420042eadf29622c9a7b7ab12221f238fe5

commit bf915420042eadf29622c9a7b7ab12221f238fe5
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date:   Wed Jan 25 18:30:50 2023 +0900

    Cygwin: dsp: Fix hang on close() if another thread calls write().
    
    fhandler_dev_dsp (OSS) has a problem that waitforallsent(), which is
    called from close(), falls into infinite loop if another thread calls
    write() accidentally after close(). This patch fixes the issue.
    
    Reviewed-by: Corinna Vinschen <corinna@vinschen.de>
    Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>

Diff:
---
 winsup/cygwin/fhandler/dsp.cc           | 9 +++++++++
 winsup/cygwin/local_includes/fhandler.h | 1 +
 2 files changed, 10 insertions(+)

diff --git a/winsup/cygwin/fhandler/dsp.cc b/winsup/cygwin/fhandler/dsp.cc
index 8798cf876..cfbf6bec7 100644
--- a/winsup/cygwin/fhandler/dsp.cc
+++ b/winsup/cygwin/fhandler/dsp.cc
@@ -1093,6 +1093,8 @@ fhandler_dev_dsp::open (int flags, mode_t)
 
   debug_printf ("ACCMODE=%y audio_in=%d audio_out=%d, err=%d, ret=%d",
 		flags & O_ACCMODE, num_in, num_out, err, ret);
+  if (ret)
+    being_closed = false;
   return ret;
 }
 
@@ -1106,6 +1108,12 @@ fhandler_dev_dsp::_write (const void *ptr, size_t len)
   int len_s = len;
   const char *ptr_s = static_cast <const char *> (ptr);
 
+  if (being_closed)
+    {
+      set_errno (EBADF);
+      return -1;
+    }
+
   if (audio_out_)
     /* nothing to do */;
   else if (IS_WRITE ())
@@ -1207,6 +1215,7 @@ int
 fhandler_dev_dsp::close ()
 {
   debug_printf ("audio_in=%p audio_out=%p", audio_in_, audio_out_);
+  being_closed = true;
   close_audio_in ();
   close_audio_out ();
   return fhandler_base::close ();
diff --git a/winsup/cygwin/local_includes/fhandler.h b/winsup/cygwin/local_includes/fhandler.h
index 113e40293..f3dd1b5a4 100644
--- a/winsup/cygwin/local_includes/fhandler.h
+++ b/winsup/cygwin/local_includes/fhandler.h
@@ -2762,6 +2762,7 @@ class fhandler_dev_dsp: public fhandler_base
   int audiochannels_;
   Audio_out *audio_out_;
   Audio_in  *audio_in_;
+  bool being_closed;
  public:
   fhandler_dev_dsp ();
   fhandler_dev_dsp *base () const {return (fhandler_dev_dsp *)archetype;}