src/patches/suse-2.6.27.25/patches.arch/ppc-spufs-06-Don-t-require-full-buffer-in-switch_l.patch

   1 Subject: Don't require full buffer in switch_log read
   2 From: Jeremy Kerr <jk@ozlabs.org>
   3 References: 447133 - LTC50070
   4
   5 Currently, read() on the sputrace log will block until the read buffer
   6 is full. This makes it difficult to retrieve the end of the buffer, as
   7 the user will need to read with the right-sized buffer.
   8
   9 In a similar method as 91553a1b5e0df006a3573a88d98ee7cd48a3818a, this
  10 change makes the switch_log return if there has already been data
  11 read.
  12
  13 Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
  14 Signed-off-by: Olaf Hering <olh@suse.de>
  15 ---
  16  arch/powerpc/platforms/cell/spufs/file.c |   46 ++++++++++++++++++-------------
  17  1 file changed, 27 insertions(+), 19 deletions(-)
  18
  19 --- a/arch/powerpc/platforms/cell/spufs/file.c
  20 +++ b/arch/powerpc/platforms/cell/spufs/file.c
  21 @@ -2506,30 +2506,38 @@ static ssize_t spufs_switch_log_read(str
  22                 char tbuf[128];
  23                 int width;
  24
  25 -               if (file->f_flags & O_NONBLOCK) {
  26 -                       if (spufs_switch_log_used(ctx) == 0) {
  27 +               if (spufs_switch_log_used(ctx) == 0) {
  28 +                       if (cnt > 0) {
  29 +                               /* If there's data ready to go, we can
  30 +                                * just return straight away */
  31 +                               break;
  32 +
  33 +                       } else if (file->f_flags & O_NONBLOCK) {
  34                                 error = -EAGAIN;
  35                                 break;
  36 +
  37 +                       } else {
  38 +                               /* spufs_wait will drop the mutex and
  39 +                                * re-acquire, but since we're in read(), the
  40 +                                * file cannot be _released (and so
  41 +                                * ctx->switch_log is stable).
  42 +                                */
  43 +                               error = spufs_wait(ctx->switch_log->wait,
  44 +                                               spufs_switch_log_used(ctx) > 0);
  45 +
  46 +                               /* On error, spufs_wait returns without the
  47 +                                * state mutex held */
  48 +                               if (error)
  49 +                                       return error;
  50 +
  51 +                               /* We may have had entries read from underneath
  52 +                                * us while we dropped the mutex in spufs_wait,
  53 +                                * so re-check */
  54 +                               if (spufs_switch_log_used(ctx) == 0)
  55 +                                       continue;
  56                         }
  57 -               } else {
  58 -                       /* spufs_wait will drop the mutex and re-acquire,
  59 -                        * but since we're in read(), the file cannot be
  60 -                        * _released (and so ctx->switch_log is stable).
  61 -                        */
  62 -                       error = spufs_wait(ctx->switch_log->wait,
  63 -                                       spufs_switch_log_used(ctx) > 0);
  64 -
  65 -                       /* On error, spufs_wait returns without the
  66 -                        * state mutex held */
  67 -                       if (error)
  68 -                               return error;
  69                 }
  70
  71 -               /* We may have had entries read from underneath us while we
  72 -                * dropped the mutex in spufs_wait, so re-check */
  73 -               if (ctx->switch_log->head == ctx->switch_log->tail)
  74 -                       continue;
  75 -
  76                 width = switch_log_sprint(ctx, tbuf, sizeof(tbuf));
  77                 if (width < len)
  78                         ctx->switch_log->tail =