From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793741046; b=Xiv17DHOkFJHmMfQI/92yO2Z/r24wGrNSBTZOgTdGe9JcwdlNskPrIgAQ4QfcGwZyAP5 QhzvyVOzF9uRr/0bA7MNkCHWt17w9GURpXlazAc5af+HeOF9DhFZnz0fityoSPZMj1gVz 4P7srcYBYldRbp1FjJ9Cy3NmjomzVq3PakQUS8z9b2Z57f4vTU+l0MH4aWM44JCerST/2 6HBTfK6UAcgni3A7cnZfswhfWtz1MM6XsQ9PIa0sNs51sHuPBzsU8ML/hQuNAS3ChjsPn 8/Eova4tXhnE1Rk/6o9pmubcmz7P1Cbld5yNcz7ZPU2pLLdDaMPmMTiD9AHiOpBb1bA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793741046; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=Yh5n57oLP82H40eUHpRLw11WTUDW/t06QuCXZP8MEvA=; b=1QGF6Xiv4227UBfDsyU3LvshMu9A31RiD0lFgS73jYmDOzL0TSV0t5KT+/7XZu1Cfcl5 eMnkqZYcrRDhis7hjp3xfzXrtbhozBEK1vP81+bTXhUMuj/fJ651knitcY8wO3kMW7kIO sMqcmUJda7EPyFKylOUV6DWahyUbRQAfL7TrFr2qvBPrYOSQNTvss4UdiX5K3yJnD8s6E yHo2zxHQ3JOY8o6abTIvpKxZQZm7VlGVb9/wx5SEJXboJQlqm+S5IdCAoW1jn88LtEvXg NKvuNJL4XrmCErWJp0/oqUpSzbWaseU3kO3laSUXd+b3OcydkVLDhdZtZ3GF20O0kDg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b="ntdO/wzm"; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4E4CD606A31B for ; Tue, 3 Nov 2026 21:24:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=ntdO/wzm Received: by smtp.kernel.org (Postfix) with ESMTPSA id C66B11F000C1; Tue, 3 Nov 2026 21:24:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793741045; bh=Yh5n57oLP82H40eUHpRLw11WTUDW/t06QuCXZP8MEvA=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=ntdO/wzmpD00u7MuGV6ShWmjksx4uy8lMc0X8q99Fgr3AA7qbSl9Sa+77PaQiQ3uH fBoK1MoFjNI6zpAVD0sTG7CFxRKVsihluTdvvGbwlQLv4zEDfPas/h/CC9IorWEMue oyFx6vxr2tvLcsMggBZZwv3VENamCa7S+/2+ExTC3ua0O4TpNZ2HuiSreqOjRGos1/ WOTB7CFy0NMKIMokh/qoTq1U6r9iynLPNGz9jIX4n1tLQA3mt+1Yp2a3SCLUF1aAX2 0DXxesvEevgURdmEfQsQd0XiySKhCvfXlUrHENWgE8GG5Iuw3dxnTmeif8ImG437tC WHzF4pl9y7kCA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v2] PCI: iproc-msi: Removed potentially endless loop handling MSI events Reply-To: sashiko-reviews@lists.linux.dev To: "Eugen Hristev" Cc: linux-pci@vger.kernel.org In-Reply-To: <20261103-iproc-irq-v2-1-dc7223df35fc@kernel.org> References: <20261103-iproc-irq-v2-1-dc7223df35fc@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 03 Nov 2026 21:24:05 +0000 X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list > The iProc MSI chained handler rereads the event queue tail after each > batch and keeps processing until the queue is empty. A continuously fed > queue can therefore keep the CPU in the handler indefinitely, starving > other interrupts and causing RCU stalls under heavy Ethernet traffic. >=20 > To fix this scenario, remove the loop that keeps reading the head and > the tail until there are no more pending events. Read the head and tail > only once and process only the events recorded in that snapshot. > Update the head before returning. Events arriving during processing > remain queued for a subsequent parent interrupt, allowing other handlers > to run without imposing an arbitrary event limit. >=20 > Discovered while testing it with an Ethernet NIC, when too many MSI > interrupts come in, CPU might get starved: >=20 > [ ... ] >=20 > With this one loop approach, IRQ handler will complete and continue > to serve MSI events on the next handler invocation. >=20 > Signed-off-by: Eugen Hristev Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261103-iproc-irq-= v2-1-dc7223df35fc@kernel.org?part=3D1