Re: [RFC PATCH v1.9 14/14] livepatch: update task universe when exiting kernel

From	Josh Poimboeuf <jpoimboe@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH v1.9 14/14] livepatch: update task universe when exiting kernel
Date	2016-04-14 15:50 +0200
Message-ID	<rnPOH-2pl-21@gated-at.bofh.it> (permalink)
References	<rgFKp-6zA-3@gated-at.bofh.it> <rgFKp-6zA-1@gated-at.bofh.it> <rnL8n-7nM-25@gated-at.bofh.it> <rnLi2-7rI-1@gated-at.bofh.it>
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On Thu, Apr 14, 2016 at 10:50:28AM +0200, Miroslav Benes wrote:
> On Thu, 14 Apr 2016, Miroslav Benes wrote:
> 
> > On Fri, 25 Mar 2016, Josh Poimboeuf wrote:
> > 
> > > Update a tasks's universe when returning from a system call or user
> > > space interrupt, or after handling a signal.
> > > 
> > > This greatly increases the chances of a patch operation succeeding.  If
> > > a task is I/O bound, it can switch universes when returning from a
> > > system call.  If a task is CPU bound, it can switch universes when
> > > returning from an interrupt.  If a task is sleeping on a to-be-patched
> > > function, the user can send SIGSTOP and SIGCONT to force it to switch.
> > > 
> > > Since the idle "swapper" tasks don't ever exit the kernel, they're
> > > updated from within the idle loop.
> > 
> > Well, I am still not familiarized enough with Andy's recent rework of 
> > entry stuff, but I think all of this is correct. Maybe I would add 
> > a note to the changelog, that since TIF_KLP_NEED_UPDATE is defined 14th 
> > bit it is also automatically included in _TIF_ALLWORK_MASKS. 
> 
> And I forgot to add that I would try to prepare similar thing for s390 and 
> maybe powerpc (taking recent development there into account). That's gonna 
> be fun :)

Yeah, good point.  I've glanced at the entry code for both architectures
and I don't think it'll be too bad, though the devil's in the details.

-- 
Josh

Thread

Re: [RFC PATCH v1.9 14/14] livepatch: update task universe when  exiting kernel Miroslav Benes <mbenes@suse.cz> - 2016-04-14 10:50 +0200
  Re: [RFC PATCH v1.9 14/14] livepatch: update task universe when  exiting kernel Miroslav Benes <mbenes@suse.cz> - 2016-04-14 11:00 +0200
    Re: [RFC PATCH v1.9 14/14] livepatch: update task universe when  exiting kernel Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-14 15:50 +0200
  Re: [RFC PATCH v1.9 14/14] livepatch: update task universe when  exiting kernel Josh Poimboeuf <jpoimboe@redhat.com> - 2016-04-14 15:30 +0200

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