From: Balbir Singh <bsingharora@gmail.com>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jessica Yu <jeyu@redhat.com>, Jiri Kosina <jikos@kernel.org>,
Miroslav Benes <mbenes@suse.cz>, Petr Mladek <pmladek@suse.com>,
linux-s390@vger.kernel.org, Vojtech Pavlik <vojtech@suse.com>,
Peter Zijlstra <peterz@infradead.org>,
x86@kernel.org, Heiko Carstens <heiko.carstens@de.ibm.com>,
linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
live-patching@vger.kernel.org, Jiri Slaby <jslaby@suse.cz>,
linuxppc-dev@lists.ozlabs.org, Ingo Molnar <mingo@kernel.org>,
Chris J Arges <chris.j.arges@canonical.com>
Subject: Re: [PATCH v3 00/15] livepatch: hybrid consistency model
Date: Sun, 11 Dec 2016 13:08:33 +1100 [thread overview]
Message-ID: <aac5fa04-c15c-5210-bce7-c72e16373964@gmail.com> (raw)
In-Reply-To: <20161210171707.cpupmxyuhob4tc3i@treble>
On 11/12/16 04:17, Josh Poimboeuf wrote:
> On Sat, Dec 10, 2016 at 04:46:17PM +1100, Balbir Singh wrote:
>> On Thu, 2016-12-08 at 12:08 -0600, Josh Poimboeuf wrote:
>>> Dusting the cobwebs off the consistency model again. This is based on
>>> linux-next/master.
>>>
>>> v1 was posted on 2015-02-09:
>>>
>>> https://lkml.kernel.org/r/cover.1423499826.git.jpoimboe@redhat.com
>>>
>>> v2 was posted on 2016-04-28:
>>>
>>> https://lkml.kernel.org/r/cover.1461875890.git.jpoimboe@redhat.com
>>>
>>> The biggest issue from v2 was finding a decent way to detect preemption
>>> and page faults on the stack of a sleeping task.
>>
>> Could you please elaborate on this? Preemption of a sleeping task and
>> faults as in the future (time) preemption and faults?
>
> The normal way for a task to go to sleep is to call schedule(). objtool
> ensures the stack trace is reliable in that case, by making sure that
> all functions save the frame pointer on the stack before calling out to
> another function.
>
> But a task can also go to sleep in a few other ways. One way is by
> preemption, where an interrupt handler interrupts the task and calls
> preempt_schedule_irq().
It's preempted, not sleeping. It's on_rq but not on_cpu.
Another way is by a page fault exception. In
> both cases, there's no guarantee that the interrupted function saved the
> frame pointer on the stack beforehand. So the stack trace might be
> unreliable. Fortunately, interrupts and exceptions leave evidence
> behind on the stack. So when walking the stack of a sleeping task, we
> can detect when an IRQ or exception occurred, and consider such a stack
> unreliable.
>
Thanks for the explanation. I presume a whole lot of this is arch specific
code? I'll look at the patches as well
Balbir
next prev parent reply other threads:[~2016-12-11 2:08 UTC|newest]
Thread overview: 78+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-08 18:08 [PATCH v3 00/15] livepatch: hybrid consistency model Josh Poimboeuf
2016-12-08 18:08 ` [PATCH v3 01/15] stacktrace/x86: add function for detecting reliable stack traces Josh Poimboeuf
2016-12-16 13:07 ` Petr Mladek
2016-12-16 22:09 ` Josh Poimboeuf
2016-12-19 16:25 ` Miroslav Benes
2016-12-19 17:25 ` Josh Poimboeuf
2016-12-19 18:23 ` Miroslav Benes
2016-12-20 9:39 ` Petr Mladek
2016-12-20 21:21 ` Josh Poimboeuf
2016-12-08 18:08 ` [PATCH v3 02/15] x86/entry: define _TIF_ALLWORK_MASK flags explicitly Josh Poimboeuf
2016-12-16 14:17 ` Petr Mladek
2016-12-16 22:13 ` Josh Poimboeuf
2016-12-19 16:39 ` Miroslav Benes
2017-01-10 8:49 ` Kamalesh Babulal
2016-12-08 18:08 ` [PATCH v3 03/15] livepatch: temporary stubs for klp_patch_pending() and klp_update_patch_state() Josh Poimboeuf
2016-12-16 14:41 ` Petr Mladek
2016-12-16 22:15 ` Josh Poimboeuf
2016-12-08 18:08 ` [PATCH v3 04/15] livepatch/x86: add TIF_PATCH_PENDING thread flag Josh Poimboeuf
2016-12-08 18:27 ` Andy Lutomirski
2016-12-16 15:39 ` Petr Mladek
2016-12-21 13:54 ` Miroslav Benes
2017-01-11 7:06 ` Kamalesh Babulal
2016-12-08 18:08 ` [PATCH v3 05/15] livepatch/powerpc: " Josh Poimboeuf
2016-12-16 16:00 ` Petr Mladek
2016-12-21 14:30 ` Miroslav Benes
2017-01-10 8:29 ` Kamalesh Babulal
2016-12-08 18:08 ` [PATCH v3 06/15] livepatch/s390: reorganize TIF thread flag bits Josh Poimboeuf
2016-12-21 15:29 ` Miroslav Benes
2016-12-08 18:08 ` [PATCH v3 07/15] livepatch/s390: add TIF_PATCH_PENDING thread flag Josh Poimboeuf
2016-12-08 18:08 ` [PATCH v3 08/15] livepatch: separate enabled and patched states Josh Poimboeuf
2016-12-16 16:21 ` Petr Mladek
2016-12-23 12:54 ` Miroslav Benes
2017-01-10 9:10 ` Kamalesh Babulal
2016-12-08 18:08 ` [PATCH v3 09/15] livepatch: remove unnecessary object loaded check Josh Poimboeuf
2016-12-16 16:26 ` Petr Mladek
2016-12-23 12:58 ` Miroslav Benes
2017-01-10 9:14 ` Kamalesh Babulal
2016-12-08 18:08 ` [PATCH v3 10/15] livepatch: move patching functions into patch.c Josh Poimboeuf
2016-12-16 16:49 ` Petr Mladek
2016-12-23 13:06 ` Miroslav Benes
2017-01-10 9:15 ` Kamalesh Babulal
2016-12-08 18:08 ` [PATCH v3 11/15] livepatch: use kstrtobool() in enabled_store() Josh Poimboeuf
2016-12-16 16:55 ` Petr Mladek
2016-12-16 22:19 ` Josh Poimboeuf
2016-12-23 13:13 ` Miroslav Benes
2016-12-08 18:08 ` [PATCH v3 12/15] livepatch: store function sizes Josh Poimboeuf
2016-12-19 13:10 ` Petr Mladek
2016-12-23 13:40 ` Miroslav Benes
2017-01-11 10:09 ` Kamalesh Babulal
2016-12-08 18:08 ` [PATCH v3 13/15] livepatch: change to a per-task consistency model Josh Poimboeuf
2016-12-20 17:32 ` Petr Mladek
2016-12-21 21:25 ` Josh Poimboeuf
2016-12-22 14:34 ` Petr Mladek
2016-12-22 18:31 ` Josh Poimboeuf
2017-01-10 13:00 ` Petr Mladek
2017-01-10 20:46 ` Josh Poimboeuf
2017-01-11 15:18 ` Petr Mladek
2017-01-11 15:26 ` Josh Poimboeuf
2016-12-23 9:24 ` Miroslav Benes
2016-12-23 10:18 ` Petr Mladek
2017-01-06 20:07 ` Josh Poimboeuf
2017-01-10 10:40 ` Petr Mladek
2017-01-04 13:44 ` Miroslav Benes
2017-01-06 21:01 ` Josh Poimboeuf
2017-01-10 10:45 ` Miroslav Benes
2017-01-05 9:34 ` Miroslav Benes
2017-01-06 21:04 ` Josh Poimboeuf
2016-12-08 18:08 ` [PATCH v3 14/15] livepatch: add /proc/<pid>/patch_state Josh Poimboeuf
2016-12-21 11:20 ` Petr Mladek
2017-01-04 14:50 ` Miroslav Benes
2016-12-08 18:08 ` [PATCH v3 15/15] livepatch: allow removal of a disabled patch Josh Poimboeuf
2016-12-21 14:44 ` Petr Mladek
2017-01-04 14:57 ` Miroslav Benes
2017-01-06 21:04 ` Josh Poimboeuf
2016-12-10 5:46 ` [PATCH v3 00/15] livepatch: hybrid consistency model Balbir Singh
2016-12-10 17:17 ` Josh Poimboeuf
2016-12-11 2:08 ` Balbir Singh [this message]
2016-12-12 14:04 ` Josh Poimboeuf
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