linux-kernel - Re: [PATCH bpf] selftests/bpf: DENYLIST.aarch64: Remove fexit

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Message-ID: <CANk7y0gYSix9fVUC1Q+DLqu8UFaJgFbxCF+_zAzjMCyFzzM4uA@mail.gmail.com>
Date: Fri, 12 Jul 2024 20:08:19 +0200
From: Puranjay Mohan <puranjay12@...il.com>
To: Manu Bretelle <chantra@...a.com>
Cc: Puranjay Mohan <puranjay@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	KP Singh <kpsingh@...nel.org>, Andrii Nakryiko <andrii@...nel.org>, 
	Eduard Zingerman <eddyz87@...il.com>, Mykola Lysenko <mykolal@...a.com>, 
	Alexei Starovoitov <ast@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Shuah Khan <shuah@...nel.org>, "bpf@...r.kernel.org" <bpf@...r.kernel.org>, 
	"linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Florent Revest <revest@...gle.com>
Subject: Re: [PATCH bpf] selftests/bpf: DENYLIST.aarch64: Remove fexit_sleep

Hi Manu,

>
> I was able to confirm the fix using the artifacts from https://github.com/kernel-patches/bpf/actions/runs/9905842936
> Thanks
>

Thanks for testing the fix.

This bug has been resolved now but the test still hangs sometimes.
Unfortunately, I am not able to reproduce this hang
using vmtest. Can you extract some logs from the CI somehow?? If it is
hanging in the kernel there should be some
soft lockup or RCU lockup related messages.

I was talking about this with Kumar and we think that this test is
hanging in the userspace in the following loop:

while (READ_ONCE(fexit_skel->bss->fentry_cnt) != 2);

Could it be that fentry_cnt is > 2 somehow before we reach this?? This
is only a random guess though.

Thanks,
Puranjay