Re: Pathological case identified from contest

From: Andrew Morton (akpm@digeo.com)
Date: Sat Oct 19 2002 - 22:05:44 EST


Con Kolivas wrote:
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On Thu, 17 Oct 2002 05:35 pm, you wrote:
> > Con Kolivas wrote:
> > > ...
> > > Well this has become more common with 2.5.43-mm2. I had to abort the
> > > process_load run 3 times when benchmarking it. Going back to other
> > > kernels and trying them it didnt happen so I dont think its my hardware
> > > failing or something like that.
> >
> > No, it's a bug in either the pipe code or the CPU scheduler I'd say.
> >
> > You could try backing out to the 2.5.40 pipe implementation; not sure if
> > that would tell us much though.
>
> I massaged the patch a little for it to apply and it _is_ the offending code.
> Backing out the pipe changes fixed the problem. I was unable to reproduce the
> holdup I was seeing with process_load even at higher data sizes. Now what?
>

Try Manfred's pipe fix I guess?

--- 2.5/fs/pipe.c Sat Oct 19 11:40:14 2002
+++ build-2.5/fs/pipe.c Sat Oct 19 19:44:04 2002
@@ -109,7 +109,7 @@
                         break;
                 }
                 if (do_wakeup) {
- wake_up_interruptible(PIPE_WAIT(*inode));
+ wake_up_interruptible_sync(PIPE_WAIT(*inode));
                          kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
                 }
                 pipe_wait(inode);
@@ -117,7 +117,7 @@
         up(PIPE_SEM(*inode));
         /* Signal writers asynchronously that there is more room. */
         if (do_wakeup) {
- wake_up_interruptible_sync(PIPE_WAIT(*inode));
+ wake_up_interruptible(PIPE_WAIT(*inode));
                 kill_fasync(PIPE_FASYNC_WRITERS(*inode), SIGIO, POLL_OUT);
         }
         if (ret > 0)
-
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