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From: zcj <zcjie0802@qq.com>
To: netdev-bot+sinfo <netdev-bot+sinfo@kernel.org>
Cc: netdev <netdev@vger.kernel.org>, mst <mst@redhat.com>,
	jasowangio <jasowangio@gmail.com>, eperezma <eperezma@redhat.com>,
	xuanzhuo <xuanzhuo@linux.alibaba.com>,
	andrew+netdev <andrew+netdev@lunn.ch>,
	davem <davem@davemloft.net>, edumazet <edumazet@kernel.org>,
	kuba <kuba@kernel.org>, pabeni <pabeni@redhat.com>,
	horms <horms@kernel.org>,
	virtualization <virtualization@lists.linux.dev>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net 1/2] net: napi: add completion with an ordered IRQ mask callback
Date: Wed, 11 Nov 2026 23:08:48 +0800	[thread overview]
Message-ID: <tencent_4DBDF69909B9FD811F54F2DC0E6BAC1C0507@qq.com> (raw)
In-Reply-To: <179440541756.2168702.17991706426089713368@kernel.org>

Hi,

I first encountered this issue on Linux 6.18.58 during a multi-threaded
TCP receive workload with virtio-net in KVM guests, and then investigated
the NAPI/virtqueue completion ordering.

The observed symptom was a persistent RX stall: the RX virtqueue had
unconsumed used entries, but notifications were disabled, NAPI had no
owner and its watchdog timer was inactive. The receiving TCP threads
remained blocked waiting for data.

A deterministic KUnit fault-injection test also reproduced the
notification-loss ordering using the production NAPI completion APIs
and watchdog. The test deliberately delays the old caller until a
successor poll has rearmed callbacks and completed. The proposed fix
passes the same test. 

The original bug report describes the symptoms and completion race:
https://lore.kernel.org/netdev/tencent_AA4F39DA7ADE330C721C03AAA832B92DD608@qq.com/

Thanks,
Congjie Zhou

  reply	other threads:[~2026-11-11 15:08 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-11-11 13:36 [BUG] virtio_net: RX stall caused by masking callbacks after NAPI ownership release Congjie Zhou
2026-11-11 13:50 ` [PATCH net 1/2] net: napi: add completion with an ordered IRQ mask callback Congjie Zhou
2026-11-11 13:56   ` netdev-bot+sinfo
2026-11-11 15:08     ` zcj [this message]
2026-11-11 13:50 ` [PATCH net 2/2] virtio_net: mask callbacks before releasing NAPI ownership Congjie Zhou

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