* cygthread.cc (cygthread::release): Reset ev here if it exists.

(cygthread::terminate_thread): Eliminat racy code which reset ev and
thread_sync.  Remove a few nonsensical inuse checks.  Exit at the bottom.
(cygthread::detach): Rewrite to again try to ensure that we don't say we're
signalled when we are not signalled.
* fhandler.cc (fhandler_base::raw_read): Revert to signalling read success
quickly.
* pipe.cc (fhandler_pipe::close): Use base method to close handle.
* sigproc.h (WAIT_SIG_PRIORITY): Just trundle along at normal priority to allow
the pipe thread to do its thing if possible.
* pinfo.h (pinfo::zap_cwd): Declare new function.
(pinfo::zap_cwd): Move 'cd out of the way code' here.
(pinfo::exit): Use it here.
* spawn.cc (spawn_guts): And here.

winsup/cygwin/spawn.cc

@@ -804,7 +804,7 @@ spawn_guts (const char * prog_arg, const char *const *argv,
 
 	 If wr_proc_pipe exists, then it should be duplicated to the child.
 	 If the child has exited already, that's ok.  The parent will pick up
-	 on this fact when we exit.  dup_proc_pipe also closes our end of the pipe.
+	 on this fact when we exit.  dup_proc_pipe will close our end of the pipe.
 	 Note that wr_proc_pipe may also be == INVALID_HANDLE_VALUE.  That will make
 	 dup_proc_pipe essentially a no-op.  */
       if (myself->wr_proc_pipe)
@@ -812,11 +812,7 @@ spawn_guts (const char * prog_arg, const char *const *argv,
 	  myself->sync_proc_pipe ();	/* Make sure that we own wr_proc_pipe
 					   just in case we've been previously
 					   execed. */
-	  SetCurrentDirectory ("c:\\");	/* Move to an innocuous location to
-					   avoid races with other processes
-					   that may want to manipulate the
-					   current directory before this process
-					   has completely exited.  */
+	  myself.zap_cwd ();
 	  (void) myself->dup_proc_pipe (pi.hProcess);
 	}
     }