linux-kernel - Re: [PATCH] 9p/xen: fix init sequence

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Message-ID: <Zz8mWwLQBNq6eopG@codewreck.org>
Date: Thu, 21 Nov 2024 21:23:55 +0900
From: Dominique Martinet <asmadeus@...ewreck.org>
To: Alexander Merritt <alexander@...ra.dev>
Cc: v9fs@...ts.linux.dev, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xenproject.org,
	Eric Van Hensbergen <ericvh@...nel.org>,
	Latchesar Ionkov <lucho@...kov.net>,
	Christian Schoenebeck <linux_oss@...debyte.com>,
	Simon Horman <horms@...nel.org>, Juergen Gross <jgross@...e.com>,
	Alex Zenla <alex@...ra.dev>, Ariadne Conill <ariadne@...adne.space>
Subject: Re: [PATCH] 9p/xen: fix init sequence

Alexander Merritt wrote on Tue, Nov 19, 2024 at 09:16:33PM +0000:
> From: Alex Zenla <alex@...ra.dev>
> 
> Large amount of mount hangs observed during hotplugging of 9pfs devices. The
> 9pfs Xen driver attempts to initialize itself more than once, causing the
> frontend and backend to disagree: the backend listens on a channel that the
> frontend does not send on, resulting in stalled processing.
> 
> Only allow initialization of 9p frontend once.

I'm not familiar with the xen bringup so I don't understand how the
patch guarantees this -- otherend_changed calls are guaranted to be
seralized for a given frontend?
I guess that at least it guaratees that we won't restart the init
process after init's been done on our side and before the remote side
sends the ack, so if you've all tested this I'll just trust you and
Juergen's review and take it as an improvement.

Queued to 9p-next; will send this to Linus in ~1week

Thanks!
-- 
Dominique