Re: [PATCH v2 7/7] tools/testing/selftests/bpf: replace open-coded 16 with TASK_COMM_LEN

From: Yafang Shao <laoar.shao@gmail.com>
To: Qais Yousef <qyousef@layalina.io>
Cc: Kajetan Puchalski <kajetan.puchalski@arm.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	John Stultz <jstultz@google.com>,
	Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Network Development <netdev@vger.kernel.org>,
	bpf <bpf@vger.kernel.org>,
	"linux-perf-use." <linux-perf-users@vger.kernel.org>,
	Linux-Fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	kernel test robot <oliver.sang@intel.com>,
	kbuild test robot <lkp@intel.com>,
	Andrii Nakryiko <andrii@kernel.org>,
	David Hildenbrand <david@redhat.com>,
	Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
	Andrii Nakryiko <andrii.nakryiko@gmail.com>,
	Michal Miroslaw <mirq-linux@rere.qmqm.pl>,
	Peter Zijlstra <peterz@infradead.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Matthew Wilcox <willy@infradead.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Kees Cook <keescook@chromium.org>, Petr Mladek <pmladek@suse.com>,
	Lukasz Luba <lukasz.luba@arm.com>,
	Qais Yousef <qyousef@google.com>,
	Daniele Di Proietto <ddiproietto@google.com>
Subject: Re: [PATCH v2 7/7] tools/testing/selftests/bpf: replace open-coded 16 with TASK_COMM_LEN
Date: Sun, 12 Feb 2023 11:19:48 +0800	[thread overview]
Message-ID: <CALOAHbBgTOU5z54GNdzCdKPcJR1Sr0T2XNCzSYOApE1A=MLDkA@mail.gmail.com> (raw)
In-Reply-To: <20230211165120.byivmbfhwyegiyae@airbuntu>

On Sun, Feb 12, 2023 at 12:51 AM Qais Yousef <qyousef@layalina.io> wrote:
>
> On 02/09/23 23:37, Yafang Shao wrote:
> > On Thu, Feb 9, 2023 at 10:28 PM Kajetan Puchalski
> > <kajetan.puchalski@arm.com> wrote:
> > >
> > > On Thu, Feb 09, 2023 at 02:20:36PM +0800, Yafang Shao wrote:
> > >
> > > [...]
> > >
> > > Hi Yafang,
> > >
> > > > Many thanks for the detailed analysis. Seems it can work.
> > > >
> > > > Hi John,
> > > >
> > > > Could you pls. try the attached fix ? I have verified it in my test env.
> > >
> > > I tested the patch on my environment where I found the issue with newer
> > > kernels + older Perfetto. The patch does improve things so that's nice.
> >
> > Thanks for the test. I don't have Perfetto in hand, so I haven't
> > verify Perfetto.
>
> FWIW, perfetto is not android specific and can run on normal linux distro setup
> (which I do but haven't noticed this breakage).
>
> It's easy to download the latest release (including for android though I never
> tried that) from github
>
>         https://github.com/google/perfetto/releases
>

Thanks for the information. I will try to run it on my test env.
I suspect the "systrace_parse_failure" error is caused by the field we
introduced into struct ftrace_event_field in the proposed patch, but I
haven't taken a deep look at the perfetto src code yet.

> Kajetan might try to see if he can pick the latest version which IIUC contains
> a workaround.
>
> If this simple patch can be tweaked to make it work again against older
> versions that'd be nice though.
>
> HTH.
>
>
> Cheers
>
> --
> Qais Yousef

-- 
Regards
Yafang