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

[Kevin Wolf <kwolf@redhat.com>]

Am 13.05.2014 um 19:44 hat Markus Armbruster geschrieben:
> Fam Zheng <famz@redhat.com> writes:
> 
> > 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                 "$@"
> >      wrote 512/512 bytes at offset 0
> >      512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> >      incompatible_features     0x1
> >
> > Any idea what the difference is here?
> 
> This is qemu-io aborting, as instructed.  The command is
> 
>     qemu-io --cache writeback --cache writethrough -c 'write -P 0x5a 0 512' -c abort scratch/t.qcow2
> 
> [...]
> 
> The additional "Aborted" line appears as soon as I put pass the qemu-io
> command to a function that runs it using "$@".  I don't need a subshell,
> exec or anything:

So that looks fine, I'd even consider it a feature to have the abort
recorded explicitly.  Let's just update the reference output. Another
reason why qemu-iotests is bash-only, but we already have the same kind
of output in other test cases, so this is not setting a precedence.

Kevin