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From: Dmitry Vyukov <dvyukov@google.com>
To: "Theodore Y. Ts'o" <tytso@mit.edu>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
	Dmitry Vyukov <dvyukov@google.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Guenter Roeck <groeck@google.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	syzkaller <syzkaller@googlegroups.com>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	David Miller <davem@davemloft.net>,
	Wu Fengguang <fengguang.wu@intel.com>
Subject: Re: what trees/branches to test on syzbot
Date: Sun, 10 Jun 2018 08:11:05 +0200	[thread overview]
Message-ID: <CACT4Y+Z-+5XhmyVcLjEf6531GKC-b+JL9kes-vjWF5PXJNvqrw@mail.gmail.com> (raw)
In-Reply-To: <20180610015107.GC5020@thunk.org>

On Sun, Jun 10, 2018 at 3:51 AM, Theodore Y. Ts'o <tytso@mit.edu> wrote:
> On Sat, Jun 09, 2018 at 03:17:21PM -0700, Linus Torvalds wrote:
>> I think it would be lovely to get linux-next back eventually, but it
>> sounds like it's just too noisy right now, and yes, we should have a
>> baseline for the standard tree first.
>>
>> But once there's a "this is known for the baseline", I think adding
>> linux-next back in and then maybe even have linux-next simply just
>> kick out trees that cause problems would be a good idea.
>>
>> Right now linux-next only kicks things out based on build issues (or
>> extreme merge issues), afaik. But it *would* be good to also have
>> things like syzbot do quality control on linux-next.
>
> Syzbot is always getting improved to find new classes of problems.  So
> the only way to get a baseline would be to use an older version of
> syzbot for linux-next, and to have it suppress sending e-mails about
> failures that are duplicates that were already found via the mainline
> tree.
>
> Then periodically, once version N has run for M weeks, and has spewed
> some large number of new failures to LKML, then you could promote
> version N to be run against linux-next, and so hopefully the only
> thing it would report against linux-next are regressions, and not
> duplicates of new bugs also being found via the latest and greatest
> version of syzbot being run against the mainline kernel.

The set of trees where a crash happened is visible on dashboard, so
one can see if it's only linux-next or whole set of trees. Potentially
syzbot can act differently depending on this predicate, but I don't
see what should be the difference. However, this does not fully save
from falsely assessing bugs as linux-next-only just because they
happened few times and only on linux-next so far. But using an older
syzkaller revision won't save from this fully either, because (1) some
bugs take long time to find, and (2) a bug can be hidden by another
known bug, so when the second bug is fixed the first one suddenly pops
up, but it's not a new bug (and the chances are that the second one
will be fixed on linux-next first, so the first bug will look like
linux-next-only).
I think re removing commits from linux-next, one of the main signals
can be: were there recent changes related to the bug. Looking at new
bugs being reported, frequently it's quite obvious (e.g.
"use-after-free in foo" and a recent "make foo faster").
But in general, if we go with linux-next, maintainers and developers
need to agree to deal with this additional aspect during bug triage.

There is also a problem with rebasing of linux-next: reported commit
hashes do not make sense and we can forget about bisection.

On a related note, recently Greg suggested to onboard more subsystem
-next trees (currently we test only net-next and bpf-next), so I tried
to formulate requirements for these trees:

https://github.com/google/syzkaller/issues/592
 - not rebased (commit hashes work, bisection works)
 - maintained in a reasonably good shape (no tons of assorted crashes)
 - reasonably active (makes sense to test)
 - merge upstream periodically (bugs are getting fixed)
 - with maintainers who are willing to cooperate and fix bugs

Any volunteers?

Thanks

  reply	other threads:[~2018-06-10  6:11 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-16  7:51 Dmitry Vyukov
2018-01-16  9:45 ` Guenter Roeck
2018-01-16  9:58   ` Dmitry Vyukov
2018-01-16 16:58     ` Guenter Roeck
2018-01-16 17:02     ` Eric W. Biederman
2018-01-16 17:34       ` Greg Kroah-Hartman
2018-01-22 13:32         ` Dmitry Vyukov
2018-06-09  6:31           ` Tetsuo Handa
2018-06-09 22:17             ` Linus Torvalds
2018-06-10  1:51               ` Theodore Y. Ts'o
2018-06-10  6:11                 ` Dmitry Vyukov [this message]
2018-06-11  1:22                   ` Theodore Y. Ts'o
2018-06-15  9:54                     ` Dmitry Vyukov
2018-06-18  4:52                       ` Stephen Rothwell
2018-06-18  6:10                       ` Eric W. Biederman
2018-06-18 13:54                       ` Alan Cox
2018-06-26 10:54               ` Tetsuo Handa
2018-06-26 14:16                 ` Theodore Y. Ts'o
2018-06-26 14:38                   ` Dmitry Vyukov
2018-06-26 14:54                     ` Guenter Roeck
2018-06-26 20:37                       ` Tetsuo Handa
2018-07-05 10:49                         ` Tetsuo Handa
2018-07-06 23:26                           ` Tetsuo Handa
2018-07-10  0:35                             ` Andrew Morton
2018-07-10  2:13                               ` Tetsuo Handa
2018-01-19  1:48     ` Fengguang Wu
2018-01-22 13:34       ` Dmitry Vyukov

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