From: Miroslav Benes <mbenes@suse.cz>
To: jpoimboe@redhat.com, jeyu@kernel.org, jikos@kernel.org
Cc: pmladek@suse.com, lpechacek@suse.cz, pavel@ucw.cz,
live-patching@vger.kernel.org, linux-kernel@vger.kernel.org,
Miroslav Benes <mbenes@suse.cz>,
Andy Lutomirski <luto@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Oleg Nesterov <oleg@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH v3 0/2] livepatch: Introduce signal and force sysfs attributes
Date: Tue, 31 Oct 2017 12:48:51 +0100 [thread overview]
Message-ID: <20171031114853.841-1-mbenes@suse.cz> (raw)
Currently, livepatch gradually migrate the system from an unpatched to a
patched state (or vice versa). Each task drops its TIF_PATCH_PENDING
itself when crossing the kernel/user space boundary or it is cleared
using the stack checking approach. If there is a task which sleeps on a
patched function, the whole transition can get stuck indefinitely.
Livepatch has means which can be used in these cases. The transition can
be cancelled and/or immediate flag may be used for the live patch. On
the other hand it might be useful to poke the system a little bit and
help the transition to finish by doing so.
That is what the fake signal can be used for. A task sleeping/waiting in
the kernel gets TIF_SIGPENDING set, it handles it and during that its
TIF_PATCH_PENDING is cleared. Kthreads are only woken up, they do not
handle signals suitably.
Still, there are cases which neither fake signal can solve. A task can
sleep uninterruptedly without reacting to signals at all. Even then, it
may be safe to clear the task's TIF_PATCH_PENDING. As a last resort,
admin may force such clearing for all tasks in the system with this
patch set.
We use the fake signal in SLES for a long time. Moreover, we don't have
a stack checking there, so we rely on the fake signal a lot. We send it
automatically and periodically.
Changes from v2:
- two sysfs attributes instead of one - Petr, Josh
- better documentation about force usage - Pavel
- small changes here and there
Changes from v1:
- better wording, typos, comments, documentation - Libor, Josh
- symbolic names in sysfs instead of numbers - Libor
- exit_to_usermode_loop(), call klp_update_patch_state() before do_signal() - Oleg
- better names - Josh
- mutex and WARN_ON_ONCE not added to klp_force_transitions() - Petr, Josh
- handle idle tasks in klp_force_transitions() too - Josh
Miroslav Benes (2):
livepatch: send a fake signal to all blocking tasks
livepatch: force transition process to finish
Documentation/ABI/testing/sysfs-kernel-livepatch | 19 +++++++
Documentation/livepatch/livepatch.txt | 21 ++++++++
arch/powerpc/kernel/signal.c | 6 +--
arch/x86/entry/common.c | 6 +--
kernel/livepatch/core.c | 54 ++++++++++++++++++++
kernel/livepatch/transition.c | 65 ++++++++++++++++++++++++
kernel/livepatch/transition.h | 2 +
kernel/signal.c | 4 +-
8 files changed, 170 insertions(+), 7 deletions(-)
--
2.14.3
next reply other threads:[~2017-10-31 11:51 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-31 11:48 Miroslav Benes [this message]
2017-10-31 11:48 ` [PATCH v3 1/2] livepatch: send a fake signal to all blocking tasks Miroslav Benes
2017-11-01 15:06 ` Miroslav Benes
2017-11-01 15:13 ` Petr Mladek
2017-11-01 16:43 ` Oleg Nesterov
2017-11-02 10:36 ` Miroslav Benes
2017-11-02 14:08 ` Oleg Nesterov
2017-11-02 13:09 ` Josh Poimboeuf
2017-11-03 8:02 ` Miroslav Benes
2017-11-03 12:57 ` Josh Poimboeuf
2017-11-02 13:32 ` Josh Poimboeuf
2017-11-03 8:06 ` Miroslav Benes
2017-11-06 11:08 ` Pavel Machek
2017-10-31 11:48 ` [PATCH v3 2/2] livepatch: force transition process to finish Miroslav Benes
2017-11-01 15:32 ` Petr Mladek
2017-11-02 13:13 ` Josh Poimboeuf
2017-11-03 8:07 ` Miroslav Benes
2017-11-06 11:11 ` Pavel Machek
2017-11-06 12:03 ` Jiri Kosina
2017-11-09 11:14 ` Pavel Machek
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=20171031114853.841-1-mbenes@suse.cz \
--to=mbenes@suse.cz \
--cc=hpa@zytor.com \
--cc=jeyu@kernel.org \
--cc=jikos@kernel.org \
--cc=jpoimboe@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=live-patching@vger.kernel.org \
--cc=lpechacek@suse.cz \
--cc=luto@kernel.org \
--cc=mingo@redhat.com \
--cc=mpe@ellerman.id.au \
--cc=oleg@redhat.com \
--cc=pavel@ucw.cz \
--cc=pmladek@suse.com \
--cc=tglx@linutronix.de \
/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).