From: ebiederm@xmission.com (Eric W. Biederman)
To: Oleg Nesterov <oleg@redhat.com>
Cc: Enke Chen <enkechen@cisco.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Arnd Bergmann <arnd@arndb.de>,
Khalid Aziz <khalid.aziz@oracle.com>,
Kate Stewart <kstewart@linuxfoundation.org>,
Helge Deller <deller@gmx.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Christian Brauner <christian@brauner.io>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Dave Martin <Dave.Martin@arm.com>,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
Michal Hocko <mhocko@kernel.org>, Rik van Riel <riel@surriel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Roman Gushchin <guro@fb.com>,
Marcos Paulo de Souza <marcos.souza.org@gmail.com>,
Dominik Brodowski <linux@dominikbrodowski.net>,
Cyrill Gorcunov <gorcunov@openvz.org>,
Yang Shi <yang.shi@linux.alibaba.com>,
Jann Horn <jannh@google.com>, Kees Cook <keescook@chromium.org>,
linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
"Victor Kamensky \(kamensky\)" <kamensky@cisco.com>,
xe-linux-external@cisco.com, Stefan Strogin <sstrogin@cisco.com>,
Eugene Syromiatnikov <esyr@redhat.com>
Subject: Re: [PATCH] kernel/signal: Signal-based pre-coredump notification
Date: Tue, 16 Oct 2018 10:09:34 -0500 [thread overview]
Message-ID: <87bm7ukjwx.fsf@xmission.com> (raw)
In-Reply-To: <20181016141405.GA22045@redhat.com> (Oleg Nesterov's message of "Tue, 16 Oct 2018 16:14:06 +0200")
Oleg Nesterov <oleg@redhat.com> writes:
> On 10/15, Enke Chen wrote:
>>
>> > I don't understand why we need valid_predump_signal() at all.
>>
>> Most of the signals have well-defined semantics, and would not be appropriate
>> for this purpose.
>
> you are going to change the rules anyway.
I will just add that CLD_XXX is only valid with SIGCHLD as they are
signal specific si_codes. In conjunction with another signal like
SIGUSR it will have another meaning. I would really appreciate it
if new code does not further complicate siginfo_layout.
>> That is why it is limited to only SIGCHLD, SIGUSR1, SIGUSR2.
>
> Which do not queue. So the parent won't get the 2nd signal if 2 children
> crash at the same time.
We do best effort queueing but we don't guarantee anything. So yes
this makes signals a very louzy interface for sending this kind of
information.
>> >> if (sig_kernel_coredump(signr)) {
>> >> + /*
>> >> + * Notify the parent prior to the coredump if the
>> >> + * parent is interested in such a notificaiton.
>> >> + */
>> >> + int p_sig = current->real_parent->predump_signal;
>> >> +
>> >> + if (valid_predump_signal(p_sig)) {
>> >> + read_lock(&tasklist_lock);
>> >> + do_notify_parent_predump(current);
>> >> + read_unlock(&tasklist_lock);
>> >> + cond_resched();
>> >
>> > perhaps this should be called by do_coredump() after coredump_wait() kills
>> > all the sub-threads?
>>
>> proc_coredump_connector(current) is located here, they should stay together.
>
> Why?
>
> Once again, other threads are still alive. So if the parent restarts the service
> after it recieves -predump_signal, the new process can "race" with the old thread.
Yes. It isn't until do_coredump calls coredump_wait that all of the
threads are killed.
Eric
next prev parent reply other threads:[~2018-10-16 15:10 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-13 0:33 [PATCH] kernel/signal: Signal-based pre-coredump notification Enke Chen
2018-10-13 6:40 ` Greg Kroah-Hartman
2018-10-15 18:16 ` Enke Chen
2018-10-15 18:43 ` Greg Kroah-Hartman
2018-10-15 18:49 ` Enke Chen
2018-10-15 18:58 ` Greg Kroah-Hartman
2018-10-13 10:44 ` Christian Brauner
2018-10-15 18:39 ` Enke Chen
2018-10-13 18:27 ` Jann Horn
2018-10-15 18:36 ` Enke Chen
2018-10-15 18:54 ` Jann Horn
2018-10-15 19:23 ` Enke Chen
2018-10-19 23:01 ` Enke Chen
2018-10-22 15:40 ` Jann Horn
2018-10-22 20:48 ` Enke Chen
2018-10-15 12:05 ` Oleg Nesterov
2018-10-15 18:54 ` Enke Chen
2018-10-15 19:17 ` Enke Chen
2018-10-15 19:26 ` Enke Chen
2018-10-16 14:14 ` Oleg Nesterov
2018-10-16 15:09 ` Eric W. Biederman [this message]
2018-10-17 0:39 ` Enke Chen
2018-10-15 21:21 ` Alan Cox
2018-10-15 21:31 ` Enke Chen
2018-10-15 23:28 ` Eric W. Biederman
2018-10-16 0:33 ` valdis.kletnieks
2018-10-16 0:54 ` Enke Chen
2018-10-16 15:26 ` Eric W. Biederman
2018-10-22 21:09 ` [PATCH v2] " Enke Chen
2018-10-23 9:23 ` Oleg Nesterov
2018-10-23 19:43 ` Enke Chen
2018-10-23 21:40 ` Enke Chen
2018-10-24 13:52 ` Oleg Nesterov
2018-10-24 21:56 ` Enke Chen
2018-10-24 5:39 ` [PATCH v3] " Enke Chen
2018-10-24 14:02 ` Oleg Nesterov
2018-10-24 22:02 ` Enke Chen
2018-10-25 22:56 ` [PATCH v4] " Enke Chen
2018-10-26 8:28 ` Oleg Nesterov
2018-10-26 22:23 ` Enke Chen
2018-10-29 11:18 ` Oleg Nesterov
2018-10-29 21:08 ` Enke Chen
2018-10-29 22:31 ` [PATCH v5] " Enke Chen
2018-10-30 16:46 ` Oleg Nesterov
2018-10-31 0:25 ` Enke Chen
2018-11-22 0:37 ` Andrew Morton
2018-11-22 1:09 ` Enke Chen
2018-11-22 1:18 ` Enke Chen
2018-11-22 1:33 ` Andrew Morton
2018-11-22 4:57 ` Enke Chen
2018-11-12 23:22 ` Enke Chen
2018-11-27 22:54 ` [PATCH v5 1/2] " Enke Chen
2018-11-28 15:19 ` Dave Martin
2018-11-29 0:15 ` Enke Chen
2018-11-29 11:55 ` Dave Martin
2018-11-30 0:27 ` Enke Chen
2018-11-30 12:03 ` Oleg Nesterov
2018-12-05 6:47 ` Jann Horn
2018-12-04 22:37 ` Andrew Morton
2018-12-06 17:29 ` Oleg Nesterov
2018-10-25 22:56 ` [PATCH] selftests/prctl: selftest for pre-coredump signal notification Enke Chen
2018-11-27 22:54 ` [PATCH v5 2/2] " Enke Chen
2018-10-24 13:29 ` [PATCH v2] kernel/signal: Signal-based pre-coredump notification Eric W. Biederman
2018-10-24 23:50 ` Enke Chen
2018-10-25 12:23 ` Eric W. Biederman
2018-10-25 20:45 ` Enke Chen
2018-10-25 21:24 ` Enke Chen
2018-10-25 21:56 ` Enke Chen
2018-10-25 13:45 ` Jann Horn
2018-10-25 20:21 ` Eric W. Biederman
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=87bm7ukjwx.fsf@xmission.com \
--to=ebiederm@xmission.com \
--cc=Dave.Martin@arm.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=bp@alien8.de \
--cc=catalin.marinas@arm.com \
--cc=christian@brauner.io \
--cc=deller@gmx.de \
--cc=enkechen@cisco.com \
--cc=esyr@redhat.com \
--cc=gorcunov@openvz.org \
--cc=gregkh@linuxfoundation.org \
--cc=guro@fb.com \
--cc=hpa@zytor.com \
--cc=jannh@google.com \
--cc=kamensky@cisco.com \
--cc=keescook@chromium.org \
--cc=khalid.aziz@oracle.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=kstewart@linuxfoundation.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@dominikbrodowski.net \
--cc=marcos.souza.org@gmail.com \
--cc=mchehab+samsung@kernel.org \
--cc=mhocko@kernel.org \
--cc=mingo@redhat.com \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=riel@surriel.com \
--cc=sstrogin@cisco.com \
--cc=tglx@linutronix.de \
--cc=viro@zeniv.linux.org.uk \
--cc=will.deacon@arm.com \
--cc=x86@kernel.org \
--cc=xe-linux-external@cisco.com \
--cc=yang.shi@linux.alibaba.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).