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Groups > linux.kernel > #1395840
| From | Josh Poimboeuf <jpoimboe@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model |
| Date | 2016-05-06 14:50 +0200 |
| Message-ID | <rvNmG-5ee-19@gated-at.bofh.it> (permalink) |
| References | <rt12N-1W5-3@gated-at.bofh.it> <rt12O-1W5-9@gated-at.bofh.it> <rvMgX-466-25@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Fri, May 06, 2016 at 01:33:01PM +0200, Petr Mladek wrote:
> On Thu 2016-04-28 15:44:48, Josh Poimboeuf wrote:
> > diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c
> > index 782fbb5..b3b8639 100644
> > --- a/kernel/livepatch/patch.c
> > +++ b/kernel/livepatch/patch.c
> > @@ -29,6 +29,7 @@
> > #include <linux/bug.h>
> > #include <linux/printk.h>
> > #include "patch.h"
> > +#include "transition.h"
> >
> > static LIST_HEAD(klp_ops);
> >
> > @@ -58,11 +59,42 @@ static void notrace klp_ftrace_handler(unsigned long ip,
> > ops = container_of(fops, struct klp_ops, fops);
> >
> > rcu_read_lock();
> > +
> > func = list_first_or_null_rcu(&ops->func_stack, struct klp_func,
> > stack_node);
> > - if (WARN_ON_ONCE(!func))
> > +
> > + if (!func)
> > goto unlock;
> >
> > + /*
> > + * See the comment for the 2nd smp_wmb() in klp_init_transition() for
> > + * an explanation of why this read barrier is needed.
> > + */
> > + smp_rmb();
> > +
> > + if (unlikely(func->transition)) {
> > +
> > + /*
> > + * See the comment for the 1st smp_wmb() in
> > + * klp_init_transition() for an explanation of why this read
> > + * barrier is needed.
> > + */
> > + smp_rmb();
>
> I would add here:
>
> WARN_ON_ONCE(current->patch_state == KLP_UNDEFINED);
>
> We do not know in which context this is called, so the printk's are
> not ideal. But it will get triggered only if there is a bug in
> the livepatch implementation. It should happen on random locations
> and rather early when a bug is introduced.
>
> Anyway, better to die and catch the bug that let the system running
> in an undefined state and produce cryptic errors later on.
Ok, makes sense.
> > + if (current->patch_state == KLP_UNPATCHED) {
> > + /*
> > + * Use the previously patched version of the function.
> > + * If no previous patches exist, use the original
> > + * function.
> > + */
> > + func = list_entry_rcu(func->stack_node.next,
> > + struct klp_func, stack_node);
> > +
> > + if (&func->stack_node == &ops->func_stack)
> > + goto unlock;
> > + }
> > + }
>
> I am staring into the code for too long now. I need to step back for a
> while. I'll do another look when you send the next version. Anyway,
> you did a great work. I speak mainly for the livepatch part and
> I like it.
Thanks for the helpful reviews! I'll be on vacation again next week so
I get a break too :-)
--
Josh
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[RFC PATCH v2 00/18] livepatch: hybrid consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
[RFC PATCH v2 14/18] livepatch: remove unnecessary object loaded check Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
[RFC PATCH v2 10/18] livepatch/powerpc: add TIF_PATCH_PENDING thread flag Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
Re: [RFC PATCH v2 10/18] livepatch/powerpc: add TIF_PATCH_PENDING thread flag Petr Mladek <pmladek@suse.com> - 2016-05-03 11:10 +0200
Re: [RFC PATCH v2 10/18] livepatch/powerpc: add TIF_PATCH_PENDING thread flag Miroslav Benes <mbenes@suse.cz> - 2016-05-03 14:10 +0200
[RFC PATCH v2 16/18] livepatch: store function sizes Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
[RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-29 20:10 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-29 22:20 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 22:30 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-29 22:40 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 23:30 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-29 23:40 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Jiri Kosina <jikos@kernel.org> - 2016-04-30 00:20 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-30 01:00 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-30 02:20 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-30 00:50 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-04-30 02:10 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-02 16:00 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-05-02 18:00 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-02 19:40 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-05-02 20:20 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Ingo Molnar <mingo@kernel.org> - 2016-05-02 20:40 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-02 21:50 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Jiri Kosina <jikos@kernel.org> - 2016-05-02 22:00 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Jiri Kosina <jikos@kernel.org> - 2016-05-02 22:10 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Andy Lutomirski <luto@amacapital.net> - 2016-05-03 02:50 +0200
RE: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking David Laight <David.Laight@ACULAB.COM> - 2016-05-04 17:20 +0200
Re: [RFC PATCH v2 05/18] sched: add task flag for preempt IRQ tracking Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 22:20 +0200
[RFC PATCH v2 09/18] livepatch/x86: add TIF_PATCH_PENDING thread flag Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
Re: [RFC PATCH v2 09/18] livepatch/x86: add TIF_PATCH_PENDING thread flag Andy Lutomirski <luto@amacapital.net> - 2016-04-29 20:10 +0200
Re: [RFC PATCH v2 09/18] livepatch/x86: add TIF_PATCH_PENDING thread flag Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 22:20 +0200
[RFC PATCH v2 02/18] x86/asm/head: use a common function for starting CPUs Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
[RFC PATCH v2 13/18] livepatch: separate enabled and patched states Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
Re: [RFC PATCH v2 13/18] livepatch: separate enabled and patched states Petr Mladek <pmladek@suse.com> - 2016-05-03 11:40 +0200
Re: [RFC PATCH v2 13/18] livepatch: separate enabled and patched states Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-03 15:50 +0200
[RFC PATCH v2 06/18] x86: dump_trace() error handling Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 22:50 +0200
Re: [RFC PATCH v2 06/18] x86: dump_trace() error handling Minfei Huang <mnghuan@gmail.com> - 2016-04-29 15:50 +0200
Re: [RFC PATCH v2 06/18] x86: dump_trace() error handling Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 16:10 +0200
[RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the stack for idle tasks Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 23:00 +0200
Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the stack for idle tasks Brian Gerst <brgerst@gmail.com> - 2016-04-29 20:50 +0200
Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the stack for idle tasks Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 22:30 +0200
Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the stack for idle tasks Andy Lutomirski <luto@kernel.org> - 2016-04-29 21:40 +0200
Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the stack for idle tasks Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-29 23:00 +0200
Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the stack for idle tasks Andy Lutomirski <luto@amacapital.net> - 2016-04-29 23:40 +0200
Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the stack for idle tasks Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-30 01:30 +0200
Re: [RFC PATCH v2 03/18] x86/asm/head: standardize the bottom of the stack for idle tasks Andy Lutomirski <luto@amacapital.net> - 2016-04-30 02:20 +0200
[RFC PATCH v2 04/18] x86: move _stext marker before head code Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 23:00 +0200
[RFC PATCH v2 01/18] x86/asm/head: clean up initial stack variable Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-28 23:00 +0200
Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-04 10:50 +0200
Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-04 18:00 +0200
Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Miroslav Benes <mbenes@suse.cz> - 2016-05-05 11:50 +0200
Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-05 15:10 +0200
barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-04 14:40 +0200
Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Peter Zijlstra <peterz@infradead.org> - 2016-05-04 16:00 +0200
Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-04 19:00 +0200
Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-04 16:20 +0200
Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-04 19:30 +0200
Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-05 13:30 +0200
Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Miroslav Benes <mbenes@suse.cz> - 2016-05-09 17:50 +0200
Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-04 19:10 +0200
Re: barriers: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-05 12:30 +0200
klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-04 16:50 +0200
Re: klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Jiri Kosina <jikos@kernel.org> - 2016-05-04 17:00 +0200
Re: klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-04 20:00 +0200
Re: klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-05 14:00 +0200
Re: klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-06 14:40 +0200
Re: klp_task_patch: was: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-09 14:30 +0200
Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Petr Mladek <pmladek@suse.com> - 2016-05-06 13:40 +0200
Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Josh Poimboeuf <jpoimboe@redhat.com> - 2016-05-06 14:50 +0200
Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Miroslav Benes <mbenes@suse.cz> - 2016-05-09 11:50 +0200
Re: [RFC PATCH v2 17/18] livepatch: change to a per-task consistency model Miroslav Benes <mbenes@suse.cz> - 2016-05-10 13:50 +0200
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