Re: [Qemu-devel] [PATCH] qemu-iotests: Fix core dump suppression in test 039

[Fam Zheng <famz@redhat.com>]

On Tue, 05/13 10:46, Markus Armbruster wrote:
> The shell script attempts to suppress core dumps like this:
> 
>     old_ulimit=$(ulimit -c)
>     ulimit -c 0
>     $QEMU_IO arg...
>     ulimit -c "$old_ulimit"
> 
> This breaks the test hard unless the limit was zero to begin with!
> ulimit sets both hard and soft limit by default, and (re-)raising the
> hard limit requires privileges.  Broken since it was added in commit
> dc68afe.
> 
> Could be fixed by adding -S to set only the soft limit, but I'm not
> sure how portable that is in practice.  Simply do it in a subshell
> instead, like this:
> 
>     (ulimit -c 0; exec $QEMU_IO arg...)
> 
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
>  tests/qemu-iotests/039 | 18 ++++++------------
>  1 file changed, 6 insertions(+), 12 deletions(-)
> 
> diff --git a/tests/qemu-iotests/039 b/tests/qemu-iotests/039
> index b9cbe99..182b0f0 100755
> --- a/tests/qemu-iotests/039
> +++ b/tests/qemu-iotests/039
> @@ -67,10 +67,8 @@ echo "== Creating a dirty image file =="
>  IMGOPTS="compat=1.1,lazy_refcounts=on"
>  _make_test_img $size
>  
> -old_ulimit=$(ulimit -c)
> -ulimit -c 0 # do not produce a core dump on abort(3)
> -$QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG" | _filter_qemu_io
> -ulimit -c "$old_ulimit"
> +(ulimit -c 0 # do not produce a core dump on abort(3)
> +exec $QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG") | _filter_qemu_io

This works well.

But when I try to put this in a function to avoid repeating:

    function _no_dump_exec()
    {
        (ulimit -c 0; exec "$@")
    }

    _no_dump_exec $QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG") | _filter_qemu_io

it doesn't work:

    039 1s ... - output mismatch (see 039.out.bad)
    --- 039.out     2014-05-13 12:10:39.248866480 +0800
    +++ 039.out.bad 2014-05-13 17:19:46.161986618 +0800
    @@ -9,6 +9,7 @@

     == Creating a dirty image file ==
     Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
    +./039: line 51: 10517 Aborted                 "$@"
     wrote 512/512 bytes at offset 0
     512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
     incompatible_features     0x1

Any idea what the difference is here?

Thanks,
Fam

>  
>  # The dirty bit must be set
>  ./qcow2.py "$TEST_IMG" dump-header | grep incompatible_features
> @@ -103,10 +101,8 @@ echo "== Opening a dirty image read/write should repair it =="
>  IMGOPTS="compat=1.1,lazy_refcounts=on"
>  _make_test_img $size
>  
> -old_ulimit=$(ulimit -c)
> -ulimit -c 0 # do not produce a core dump on abort(3)
> -$QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG" | _filter_qemu_io
> -ulimit -c "$old_ulimit"
> +(ulimit -c 0 # do not produce a core dump on abort(3)
> +exec $QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG") | _filter_qemu_io
>  
>  # The dirty bit must be set
>  ./qcow2.py "$TEST_IMG" dump-header | grep incompatible_features
> @@ -122,10 +118,8 @@ echo "== Creating an image file with lazy_refcounts=off =="
>  IMGOPTS="compat=1.1,lazy_refcounts=off"
>  _make_test_img $size
>  
> -old_ulimit=$(ulimit -c)
> -ulimit -c 0 # do not produce a core dump on abort(3)
> -$QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG" | _filter_qemu_io
> -ulimit -c "$old_ulimit"
> +(ulimit -c 0 # do not produce a core dump on abort(3)
> +exec $QEMU_IO -c "write -P 0x5a 0 512" -c "abort" "$TEST_IMG") | _filter_qemu_io
>  
>  # The dirty bit must not be set since lazy_refcounts=off
>  ./qcow2.py "$TEST_IMG" dump-header | grep incompatible_features
> -- 
> 1.8.1.4
> 
>