From: Thomas Monjalon <thomas@monjalon.net>
To: "Mattias Rönnblom" <hofors@lysator.liu.se>,
"Mattias Rönnblom" <mattias.ronnblom@ericsson.com>
Cc: dev@dpdk.org, Jerin Jacob <jerinj@marvell.com>,
dpdk stable <stable@dpdk.org>,
Jerin Jacob <jerinjacobk@gmail.com>
Subject: Re: [PATCH] event/dsw: fix migration bug
Date: Mon, 11 Jul 2022 22:43:22 +0200 [thread overview]
Message-ID: <3811024.d4nMDBE73Y@thomas> (raw)
In-Reply-To: <CALBAE1O9EpvPsj_nZ=G0kEvrXpLhMZRpqW+2u9QwmsnkO=V5Cg@mail.gmail.com>
11/07/2022 14:45, Jerin Jacob:
> On Thu, Jul 7, 2022 at 5:13 PM Mattias Rönnblom <hofors@lysator.liu.se> wrote:
> >
> > From: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
> >
> > Fix bug in flow migration, which under certain conditions causes
> > reordering and violation of atomicity guarantees.
> >
> > The issue occurs when the processing of a flow (on an atomic queue)
> > has resulted in events enqueued to a flow currently being migrated,
> > and the former (producer) flow is also selected for migration. The
> > events are buffered ("paused") on the originating port, and released
> > (forwarded) when the migration has completed. However, at the time of
> > "unpausing" the latter (consumer) flow, processing of the producer
> > flow on the port to which it was migrated may have already produced
> > events, for the same paused flow. This constitutes a race condition,
> > and depending on which port wins, reordering may have been introduced.
> >
> > This patch forbids migration when a port has paused events, since
> > those events may have been the result of processing a to-be-migrated
> > flow.
> >
> > This patch also disallows processing events pertaining to a flow under
> > migration, for the same reason. A new buffer is introduced, which
> > holds such not-yet-processed events dequeued from the port's input
> > ring. Such events are forwarded to the target port as a part of the
> > migration process.
> >
> > The 'forwarding' migration state is eliminated, and instead background
> > processing is only performed if there are no unreleased events on the
> > port.
> >
> > The bug is primarily triggered in situations where multiple flows are
> > migrated as one transaction, but may occur even if only a single flow
> > is migrated (e.g., with older DSW versions, which does not support
> > multi-flow migration).
> >
> > Fixes: f6257b22e767 ("event/dsw: add load balancing")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
>
> + @Thomas Monjalon to merge to the main tree directly.
No sorry,
it would not be serious to merge such a big patch in the last minute.
And it is not a new bug.
next prev parent reply other threads:[~2022-07-11 20:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-07 11:43 Mattias Rönnblom
2022-07-11 12:45 ` Jerin Jacob
2022-07-11 20:43 ` Thomas Monjalon [this message]
2022-09-13 12:53 ` Jerin Jacob
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