Re: [External] : Re: [PATCH 6.6.y] selftests/bpf: Remove flaky test_btf_id test

[Greg KH <greg@kroah.com>]

On Fri, Feb 02, 2024 at 05:33:36PM -0800, samasth.norway.ananda@oracle.com wrote:
> 
> 
> On 2/2/24 5:31 PM, Greg KH wrote:
> > On Thu, Feb 01, 2024 at 07:45:45PM -0800, Samasth Norway Ananda wrote:
> > > From: Yonghong Song <yonghong.song@linux.dev>
> > > 
> > > [ Upstream commit 56925f389e152dcb8d093435d43b78a310539c23 ]
> > > 
> > > With previous patch, one of subtests in test_btf_id becomes
> > > flaky and may fail. The following is a failing example:
> > > 
> > >    Error: #26 btf
> > >    Error: #26/174 btf/BTF ID
> > >      Error: #26/174 btf/BTF ID
> > >      btf_raw_create:PASS:check 0 nsec
> > >      btf_raw_create:PASS:check 0 nsec
> > >      test_btf_id:PASS:check 0 nsec
> > >      ...
> > >      test_btf_id:PASS:check 0 nsec
> > >      test_btf_id:FAIL:check BTF lingersdo_test_get_info:FAIL:check failed: -1
> > > 
> > > The test tries to prove a btf_id not available after the map is closed.
> > > But btf_id is freed only after workqueue and a rcu grace period, compared
> > > to previous case just after a rcu grade period.
> > > Depending on system workload, workqueue could take quite some time
> > > to execute function bpf_map_free_deferred() which may cause the test failure.
> > > Instead of adding arbitrary delays, let us remove the logic to
> > > check btf_id availability after map is closed.
> > > 
> > > Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
> > > Link: https://urldefense.com/v3/__https://lore.kernel.org/r/20231214203820.1469402-1-yonghong.song@linux.dev__;!!ACWV5N9M2RV99hQ!I-3G5NyOo-Xom0b0NmUHYWm_hs6Ai1qD4A9smNew_5_8jyyEXbISpxoAPa4wSD_eXQr-IOAd4_TM2NBscejS$
> > > Signed-off-by: Alexei Starovoitov <ast@kernel.org>
> > > [Samasth: backport for 6.6.y]
> > > Signed-off-by: Samasth Norway Ananda <samasth.norway.ananda@oracle.com>
> > > ---
> > > Above patch is a fix for 59e5791f59dd ("bpf: Fix a race condition between
> > > btf_put() and map_free()"). While the commit causing the error is
> > > present in 6.6.y the fix is not present.
> > > ---
> > >   tools/testing/selftests/bpf/prog_tests/btf.c | 5 -----
> > >   1 file changed, 5 deletions(-)
> > 
> > What about 6.7 as well?  Shouldn't this change be there too?
> 
> Yes, it should be there on 6.7 as well. Sorry, I should have mentioned that.

thanks, now queued up.

greg k-h