Re: [Qemu-devel] [Qemu-block] [PATCH for-2.5?] qemu-iotests: Reduce racy output in 028

[John Snow]

On 12/10/2015 10:27 PM, Eric Blake wrote:
> On my machine, './check -qcow2 028' was failing about 80% of the
> time, due to a race in how many times the repeated attempts
> to run 'info block-jobs' could occur before the job was done,
> showing up as a failure of fewer '(qemu) ' prompts than in the
> expected output.  Silence the output during the repetitions, then
> add a final clean command to keep the expected output useful;
> once patched, I was finally able to run the test 20 times in a
> row with no failures.
> 

Son of a gun:

028 4s ... - output mismatch (see 028.out.bad)
--- /home/bos/jsnow/src/q3mu/tests/qemu-iotests/028.out 2015-10-09
13:33:06.823758271 -0400
+++ 028.out.bad 2015-12-11 20:12:23.688952510 -0500
@@ -470,7 +470,7 @@

 Formatting 'TEST_DIR/t.IMGFMT.copy', fmt=IMGFMT size=4294968832
backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 (qemu)
-(qemu) info block-jobs
+info block-jobs
 Type backup, device disk: Completed 0 of 4294968832 bytes, speed limit
0 bytes/s
 info block-jobs
 No active jobs


Something must have changed to make it more prone to races, somehow.
Venus... Swamp gas...

> Signed-off-by: Eric Blake <address@hidden>
> ---
> 
> Not sure if this is the best fix, or if it is even appropriate
> for inclusion in 2.5 this late in the game.
> 
>  tests/qemu-iotests/028     | 6 ++++--
>  tests/qemu-iotests/028.out | 3 ---
>  2 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/tests/qemu-iotests/028 b/tests/qemu-iotests/028
> index a1f4423..756c335 100755
> --- a/tests/qemu-iotests/028
> +++ b/tests/qemu-iotests/028
> @@ -111,10 +111,12 @@ h=$QEMU_HANDLE
>  QEMU_COMM_TIMEOUT=1
> 
>  # Silence output since it contains the disk image path and QEMU's readline
> -# character echoing makes it very hard to filter the output
> +# character echoing makes it very hard to filter the output. Plus, there
> +# is no telling how many times the command will repeat before succeeding.
>  _send_qemu_cmd $h "drive_backup disk ${TEST_IMG}.copy" "(qemu)" >/dev/null
>  _send_qemu_cmd $h "" "Formatting" | _filter_img_create
> -qemu_cmd_repeat=20 _send_qemu_cmd $h "info block-jobs" "No active jobs"
> +qemu_cmd_repeat=20 _send_qemu_cmd $h "info block-jobs" "No active jobs" 
> >/dev/null
> +_send_qemu_cmd $h "info block-jobs" "No active jobs"
>  _send_qemu_cmd $h 'quit' ""
> 
>  # Base image sectors
> diff --git a/tests/qemu-iotests/028.out b/tests/qemu-iotests/028.out
> index 29c9972..e03452d 100644
> --- a/tests/qemu-iotests/028.out
> +++ b/tests/qemu-iotests/028.out
> @@ -469,10 +469,7 @@ No errors were found on the image.
>  block-backup
> 
>  Formatting 'TEST_DIR/t.IMGFMT.copy', fmt=IMGFMT size=4294968832 
> backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
> -(qemu)
>  (qemu) iininfinfoinfo 
> info binfo 
> blinfo bloinfo 
> blocinfo 
> blockinfo 
> block-info 
> block-jinfo 
> block-joinfo 
> block-jobinfo block-jobs
> -Type backup, device disk: Completed 0 of 4294968832 bytes, speed limit 0 
> bytes/s
> -iininfinfoinfo 
> info binfo 
> blinfo bloinfo 
> blocinfo 
> blockinfo 
> block-info 
> block-jinfo 
> block-joinfo 
> block-jobinfo block-jobs
>  No active jobs
>  === IO: pattern 195
>  read 512/512 bytes at offset 3221194240
>