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From: Jerin Jacob <jerinjacobk@gmail.com>
To: "Mattias Rönnblom" <hofors@lysator.liu.se>
Cc: "Jerin Jacob" <jerinj@marvell.com>,
	dev@dpdk.org, "Mattias Rönnblom" <mattias.ronnblom@ericsson.com>,
	stable@dpdk.org
Subject: Re: [PATCH] event/dsw: fix migration bug
Date: Tue, 13 Sep 2022 18:23:09 +0530	[thread overview]
Message-ID: <CALBAE1M3F4qkDYH+fz1x4H+6b6UT_SjeVhm3UfJyEP1uuB1HkQ@mail.gmail.com> (raw)
In-Reply-To: <20220707114325.3098735-1-hofors@lysator.liu.se>

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>


Applied to dpdk-next-net-eventdev/for-main. Thanks

      parent reply	other threads:[~2022-09-13 12:53 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
2022-09-13 12:53 ` Jerin Jacob [this message]

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