From: Peter Xu <peterx@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Prasad Pandit <ppandit@redhat.com>,
qemu-devel@nongnu.org, Fabiano Rosas <farosas@suse.de>,
Jason Wang <jasowang@redhat.com>,
mcoqueli@redhat.com, Prasad Pandit <pjp@fedoraproject.org>
Subject: Re: [PATCH 0/2] Postcopy migration and vhost-user errors
Date: Wed, 17 Jul 2024 09:33:01 -0400 [thread overview]
Message-ID: <ZpfIDUwS9vawpzT5@x1n> (raw)
In-Reply-To: <20240717045335-mutt-send-email-mst@kernel.org>
Hi, Michael,
On Wed, Jul 17, 2024 at 04:55:52AM -0400, Michael S. Tsirkin wrote:
> I just want to understand how we managed to have two threads
> talking in parallel. BQL is normally enough, which path
> manages to invoke vhost-user with BQL not taken?
> Just check BQL taken on each vhost user invocation and
> you will figure it out.
Prasad mentioned how the race happened in the cover letter:
https://lore.kernel.org/r/20240711131424.181615-1-ppandit@redhat.com
Thread-1 Thread-2
vhost_dev_start postcopy_ram_incoming_cleanup
vhost_device_iotlb_miss postcopy_notify
vhost_backend_update_device_iotlb vhost_user_postcopy_notifier
vhost_user_send_device_iotlb_msg vhost_user_postcopy_end
process_message_reply process_message_reply
vhost_user_read vhost_user_read
vhost_user_read_header vhost_user_read_header
"Fail to update device iotlb" "Failed to receive reply to postcopy_end"
The normal case should be that thread-2 is postcopy_ram_listen_thread(),
and this happens when postcopy migration is close to the end.
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2024-07-17 13:33 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-07-11 13:14 [PATCH 0/2] Postcopy migration and vhost-user errors Prasad Pandit
2024-07-11 13:14 ` [PATCH 1/2] vhost-user: add a write-read lock Prasad Pandit
2024-07-11 14:39 ` Michael S. Tsirkin
2024-07-15 10:57 ` Prasad Pandit
2024-07-11 15:41 ` Peter Xu
2024-07-15 8:14 ` Prasad Pandit
2024-07-15 13:27 ` Peter Xu
2024-07-16 10:19 ` Prasad Pandit
2024-07-20 19:41 ` Michael S. Tsirkin
2024-07-23 4:58 ` Prasad Pandit
2024-07-11 13:14 ` [PATCH 2/2] vhost: fail device start if iotlb update fails Prasad Pandit
2024-07-11 15:38 ` [PATCH 0/2] Postcopy migration and vhost-user errors Peter Xu
2024-07-15 10:14 ` Prasad Pandit
2024-07-15 13:39 ` Peter Xu
2024-07-16 10:14 ` Prasad Pandit
2024-07-16 22:02 ` Peter Xu
2024-07-17 8:55 ` Michael S. Tsirkin
2024-07-17 13:33 ` Peter Xu [this message]
2024-07-17 13:40 ` Michael S. Tsirkin
2024-07-17 13:47 ` Peter Xu
2024-07-20 19:41 ` Michael S. Tsirkin
2024-07-23 5:03 ` Prasad Pandit
2024-07-23 17:52 ` Peter Xu
2024-07-23 17:57 ` Prasad Pandit
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