On Tue, 9 Aug 2022 at 18:01, Yonghong Song <yhs@xxxxxx> wrote:
> On 8/9/22 7:06 AM, Kumar Kartikeya Dwivedi wrote:
> > Add a regression test to check against invalid check_and_init_map_value
> > call inside prealloc_lru_pop.
> >
> > To actually observe a kind of problem this can cause, set debug to 1
> > when running the test locally without the fix. Then, just observe the
> > refcount which keeps increasing on each run of the test. With timers or
> > spin locks, it would cause unpredictable results when racing.
> >
> > ...
> >
> > bash-5.1# ./test_progs -t lru_bug
> > test_progs-192 [000] d..21 354.838821: bpf_trace_printk: ref: 4
> > test_progs-192 [000] d..21 354.842824: bpf_trace_printk: ref: 5
> > bash-5.1# ./test_progs -t lru_bug
> > test_progs-193 [000] d..21 356.722813: bpf_trace_printk: ref: 5
> > test_progs-193 [000] d..21 356.727071: bpf_trace_printk: ref: 6
> >
> > ... and so on.
> >
> > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
>
> Ack with a minor nit below.
>
> Acked-by: Yonghong Song <yhs@xxxxxx>
>
> > ---
> > .../selftests/bpf/prog_tests/lru_bug.c | 19 ++++++
> > tools/testing/selftests/bpf/progs/lru_bug.c | 67 +++++++++++++++++++
> > 2 files changed, 86 insertions(+)
> > create mode 100644 tools/testing/selftests/bpf/prog_tests/lru_bug.c
> > create mode 100644 tools/testing/selftests/bpf/progs/lru_bug.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/lru_bug.c b/tools/testing/selftests/bpf/prog_tests/lru_bug.c
> > new file mode 100644
> > index 000000000000..3bcb5bc62d5a
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/lru_bug.c
> > @@ -0,0 +1,19 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <test_progs.h>
> > +
> > +#include "lru_bug.skel.h"
> > +
> > +void serial_test_lru_bug(void)
> > +{
> > + struct lru_bug *skel;
> > + int ret;
> > +
> > + skel = lru_bug__open_and_load();
> > + if (!ASSERT_OK_PTR(skel, "lru_bug__open_and_load"))
> > + return;
> > + ret = lru_bug__attach(skel);
> > + if (!ASSERT_OK(ret, "lru_bug__attach"))
> > + return;
>
> If not ASSERT_OK, should go to lru_bug__destroy(skel).
>
> > + usleep(1);
> > + ASSERT_OK(skel->data->result, "prealloc_lru_pop doesn't call check_and_init_map_value");
>
> Missing
> lru_bug__destroy(skel);
Oops, thanks for catching, will fix.
> .
>
> > +}
> [...]
