From: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
To: Yafang Shao <laoar.shao@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Kees Cook <keescook@chromium.org>,
Steven Rostedt <rostedt@goodmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>,
Petr Mladek <pmladek@suse.com>,
Peter Zijlstra <peterz@infradead.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Valentin Schneider <valentin.schneider@arm.com>,
Qiang Zhang <qiang.zhang@windriver.com>,
robdclark <robdclark@chromium.org>,
christian <christian@brauner.io>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ingo Molnar <mingo@redhat.com>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
David Miller <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>, Martin Lau <kafai@fb.com>,
Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
john fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
dennis.dalessandro@cornelisnetworks.com,
mike.marciniszyn@cornelisnetworks.com, dledford@redhat.com,
jgg@ziepe.ca, linux-rdma@vger.kernel.org,
netdev <netdev@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
"linux-perf-use." <linux-perf-users@vger.kernel.org>,
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>
Subject: Re: [PATCH v7 00/11] extend task comm from 16 to 24
Date: Sat, 6 Nov 2021 12:29:51 +0100 [thread overview]
Message-ID: <YYZnL58B+GsNypEn@qmqm.qmqm.pl> (raw)
In-Reply-To: <CALOAHbAP5qhKjsgwhekcDcutWpHMsxxGfB+K1-=2RyOyJt9MeQ@mail.gmail.com>
On Sat, Nov 06, 2021 at 05:12:24PM +0800, Yafang Shao wrote:
> On Sat, Nov 6, 2021 at 7:57 AM Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote:
> >
> > On Fri, Nov 05, 2021 at 02:34:58PM +0800, Yafang Shao wrote:
> > > On Thu, Nov 4, 2021 at 9:37 AM Michał Mirosław <mirq-linux@rere.qmqm.pl> wrote:
> > > >
> > > > On Mon, Nov 01, 2021 at 06:04:08AM +0000, Yafang Shao wrote:
> > > > > There're many truncated kthreads in the kernel, which may make trouble
> > > > > for the user, for example, the user can't get detailed device
> > > > > information from the task comm.
> > > > >
> > > > > This patchset tries to improve this problem fundamentally by extending
> > > > > the task comm size from 16 to 24, which is a very simple way.
> > > > [...]
> > > >
> > > > Hi,
> > > >
> > > > I've tried something like this a few years back. My attempt got mostly
> > > > lost in the mailing lists, but I'm still carrying the patches in my
> > > > tree [1]. My target was userspace thread names, and it turned out more
> > > > involved than I had time for.
> > > >
> > > > [1] https://rere.qmqm.pl/git/?p=linux;a=commit;h=2c3814268caf2b1fee6d1a0b61fd1730ce135d4a
> > > > and its parents
> > > >
> > >
> > > Hi Michal,
> > >
> > > Thanks for the information.
> > >
> > > I have looked through your patches. It seems to contain six patches
> > > now and can be divided into three parts per my understanding.
> > >
> > > 1. extend task comm len
> > > This parts contains below 4 patches:
> > > [prctl: prepare for bigger
> > > TASK_COMM_LEN](https://rere.qmqm.pl/git/?p=linux;a=commit;h=cfd99db9cf911bb4d106889aeba1dfe89b6527d0)
> > > [bluetooth: prepare for bigger
> > > TASK_COMM_LEN](https://rere.qmqm.pl/git/?p=linux;a=commit;h=ba2805f5196865b81cc6fc938ea53af2c7c2c892)
> > > [taskstats: prepare for bigger
> > > TASK_COMM_LEN](https://rere.qmqm.pl/git/?p=linux;a=commit;h=4d29bfedc57b36607915a0171f4864ec504908ca)
> > > [mm: make TASK_COMM_LEN
> > > configurable](https://rere.qmqm.pl/git/?p=linux;a=commit;h=362acc35582445174589184c738c4d86ec7d174b)
> > >
> > > What kind of userspace issues makes you extend the task comm length ?
> > > Why not just use /proc/[pid]/cmdline ?
> >
> > This was to enable longer thread names (as set by pthread_setname_np()).
> > Currently its 16 bytes, and that's too short for e.g. Chrome's or Firefox'es
> > threads. I believe that FreeBSD has 32-byte limit and so I expect that
> > major portable code is already prepared for bigger thread names.
> >
>
> The comm len in FreeBSD is (19 + 1) bytes[1], but that is still larger
> than Linux :)
> The task comm is short for many applications, that is why cmdline is
> introduced per my understanding, but pthread_{set, get}name_np() is
> reading/writing the comm or via prctl(2) rather than reading/writing
> the cmdline...
>
> Is the truncated Chrome or Firefox thread comm really harmful or is
> extending the task comm just for portable?
> Could you pls show me some examples if the short comm is really harmful?
>
> Per my understanding, if the short comm is harmful to applications
> then it is worth extending it.
> But if it is only for portable code, it may not be worth extending it.
>
> [1]. https://github.com/freebsd/freebsd-src/blob/main/sys/sys/param.h#L126
I don't think it is harmful as in exposing a bug or something. It's just
inconvenient when debugging a system where you can't differentiate
between threads because their names have been cut too short.
Best Regards
Michał Mirosław
prev parent reply other threads:[~2021-11-06 11:30 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-01 6:04 [PATCH v7 00/11] extend task comm from 16 to 24 Yafang Shao
2021-11-01 6:04 ` [PATCH v7 01/11] fs/exec: make __set_task_comm always set a nul terminated string Yafang Shao
2021-11-01 6:04 ` [PATCH v7 02/11] fs/exec: make __get_task_comm always get " Yafang Shao
2021-11-01 6:04 ` [PATCH v7 03/11] sched.h: use __must_be_array instead of BUILD_BUG_ON in get_task_comm Yafang Shao
2021-11-01 6:04 ` [PATCH v7 04/11] drivers/infiniband: make setup_ctxt always get a nul terminated task comm Yafang Shao
2021-11-01 6:04 ` [PATCH v7 05/11] fs/binfmt_elf: make prpsinfo " Yafang Shao
2021-11-01 6:04 ` [PATCH v7 06/11] samples/bpf/test_overhead_kprobe_kern: make it adopt to task comm size change Yafang Shao
2021-11-01 6:04 ` [PATCH v7 07/11] tools/bpf/bpftool/skeleton: " Yafang Shao
2021-11-01 23:47 ` Andrii Nakryiko
2021-11-01 6:04 ` [PATCH v7 08/11] tools/perf/test: make perf test " Yafang Shao
2021-11-17 14:31 ` Arnaldo Carvalho de Melo
2021-11-18 14:18 ` Yafang Shao
2021-11-01 6:04 ` [PATCH v7 09/11] tools/testing/selftests/bpf: make it " Yafang Shao
2021-11-01 23:47 ` Andrii Nakryiko
2021-11-01 6:04 ` [PATCH v7 10/11] sched.h: extend task comm from 16 to 24 Yafang Shao
2021-11-01 6:04 ` [PATCH v7 11/11] kernel/kthread: show a warning if kthread's comm is truncated Yafang Shao
2021-11-01 12:44 ` [PATCH v7 00/11] extend task comm from 16 to 24 Matthew Wilcox
2021-11-01 13:12 ` Yafang Shao
2021-11-01 14:07 ` Petr Mladek
2021-11-01 14:34 ` Yafang Shao
2021-11-01 16:02 ` Petr Mladek
2021-11-01 16:06 ` Steven Rostedt
2021-11-02 1:09 ` Yafang Shao
2021-11-02 1:18 ` Steven Rostedt
2021-11-02 1:26 ` Yafang Shao
2021-11-02 7:56 ` Petr Mladek
2021-11-02 13:48 ` Yafang Shao
2021-11-02 9:26 ` David Hildenbrand
2021-11-04 1:37 ` Michał Mirosław
2021-11-05 6:34 ` Yafang Shao
2021-11-05 23:57 ` Michał Mirosław
2021-11-06 9:12 ` Yafang Shao
2021-11-06 11:29 ` Michał Mirosław [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YYZnL58B+GsNypEn@qmqm.qmqm.pl \
--to=mirq-linux@rere.qmqm.pl \
--cc=akpm@linux-foundation.org \
--cc=andrii@kernel.org \
--cc=arnaldo.melo@gmail.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=christian@brauner.io \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=dennis.dalessandro@cornelisnetworks.com \
--cc=dietmar.eggemann@arm.com \
--cc=dledford@redhat.com \
--cc=jgg@ziepe.ca \
--cc=john.fastabend@gmail.com \
--cc=juri.lelli@redhat.com \
--cc=kafai@fb.com \
--cc=keescook@chromium.org \
--cc=kpsingh@kernel.org \
--cc=kuba@kernel.org \
--cc=laoar.shao@gmail.com \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=lkp@intel.com \
--cc=mathieu.desnoyers@efficios.com \
--cc=mike.marciniszyn@cornelisnetworks.com \
--cc=mingo@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=oliver.sang@intel.com \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=qiang.zhang@windriver.com \
--cc=robdclark@chromium.org \
--cc=rostedt@goodmis.org \
--cc=songliubraving@fb.com \
--cc=valentin.schneider@arm.com \
--cc=vincent.guittot@linaro.org \
--cc=viro@zeniv.linux.org.uk \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).