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SubjectRe: [PATCH 0/2] vhost: improve livepatch switching for heavily loaded vhost worker kthreads
On Thu, Jan 26, 2023 at 03:12:35PM -0600, Seth Forshee (DigitalOcean) wrote:
> On Thu, Jan 26, 2023 at 06:03:16PM +0100, Petr Mladek wrote:
> > On Fri 2023-01-20 16:12:20, Seth Forshee (DigitalOcean) wrote:
> > > We've fairly regularaly seen liveptches which cannot transition within kpatch's
> > > timeout period due to busy vhost worker kthreads.
> >
> > I have missed this detail. Miroslav told me that we have solved
> > something similar some time ago, see
> > https://lore.kernel.org/all/20220507174628.2086373-1-song@kernel.org/
>
> Interesting thread. I had thought about something along the lines of the
> original patch, but there are some ideas in there that I hadn't
> considered.

Here's another idea, have we considered this? Have livepatch set
TIF_NEED_RESCHED on all kthreads to force them into schedule(), and then
have the scheduler call klp_try_switch_task() if TIF_PATCH_PENDING is
set.

Not sure how scheduler folks would feel about that ;-)

--
Josh

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