[ECOS] Starvation in cyg_libc_stdio_flush_all_but()?

[David Airlie]

I think I had something like this fixed by

diff -u -r1.1 -r1.2
--- ecos/packages/language/c/libc/stdio/current/src/common/fflush.cxx	2001/04/19 16:06:09	1.1
+++ ecos/packages/language/c/libc/stdio/current/src/common/fflush.cxx	2001/12/03 15:27:25	1.2
@@ -86,7 +86,10 @@
                 } // if
                 else {
                     // valid stream
-
+#ifdef CYGSEM_LIBC_STDIO_WANT_BUFFERED_IO
+		  if(!stream->flags.last_buffer_op_was_read)
+#endif
+		  {
                     if ( stream->trylock_me() ) {
                         err = stream->flush_output_unlocked();
                         stream->unlock_me();
@@ -94,6 +97,7 @@
                     } // if
                     else
                         loop_again = true;
+		  }
                 } // else
             } // if
         } // for

this is in CVS at the time I found it in my tree.. so I just stole the fix
from CVS..

let me know if it works..

Dave.

On 3 Dec 2001, Robin Farine wrote:

> Hi,
>
> Under some circumstances, my application's UI freezes but background threads
> still run. The following scenario causes it to happen:
>
>   1. Two threads; one, called CLI, handles the command line interface. The
>      second, say WRK, does some work and prints messages to the console.
>
>   2. priority(CLI) > priority(WRK)    (higher priority, not higher value)
>
>   3. While WRK is printing a message to stdout, the user hits RETURN which
>      causes the CLI thread to wake up and display a prompt to stderr. This ends
>      in cyg_libc_stdio_flush_all_but() with the CLI thread looping endlessly
>      trying to flush stdout since WRK owns stdout stream's lock and cannot
>      release it because of its lower priority.
>
> Did anyone already have this problem? Do the current CVS sources fix it?
>
>
> Thanks,
>
> Robin
>

-- 
      David Airlie, Software Engineer, Parthus Technologies plc.,
       Mary Rosse Centre, National Tech Park, Limerick, Ireland.
   t: +353-61-508116 / f: +353-61-508101 / David.Airlie@parthus.com