linux-kernel - Re: [PATCH net-next,v7] net: mana: Add handler for hardware servicing events

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Message-ID:
 <SN6PR2101MB0943E22270089F2B8A6E9A04CA77A@SN6PR2101MB0943.namprd21.prod.outlook.com>
Date: Fri, 13 Jun 2025 17:06:55 +0000
From: Haiyang Zhang <haiyangz@...rosoft.com>
To: Jakub Kicinski <kuba@...nel.org>, Haiyang Zhang
	<haiyangz@...ux.microsoft.com>
CC: "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, Dexuan Cui
	<decui@...rosoft.com>, "stephen@...workplumber.org"
	<stephen@...workplumber.org>, KY Srinivasan <kys@...rosoft.com>, Paul
 Rosswurm <paulros@...rosoft.com>, "olaf@...fle.de" <olaf@...fle.de>,
	"vkuznets@...hat.com" <vkuznets@...hat.com>, "davem@...emloft.net"
	<davem@...emloft.net>, "wei.liu@...nel.org" <wei.liu@...nel.org>,
	"edumazet@...gle.com" <edumazet@...gle.com>, "pabeni@...hat.com"
	<pabeni@...hat.com>, "leon@...nel.org" <leon@...nel.org>, Long Li
	<longli@...rosoft.com>, "ssengar@...ux.microsoft.com"
	<ssengar@...ux.microsoft.com>, "linux-rdma@...r.kernel.org"
	<linux-rdma@...r.kernel.org>, "daniel@...earbox.net" <daniel@...earbox.net>,
	"john.fastabend@...il.com" <john.fastabend@...il.com>, "bpf@...r.kernel.org"
	<bpf@...r.kernel.org>, "ast@...nel.org" <ast@...nel.org>, "hawk@...nel.org"
	<hawk@...nel.org>, "tglx@...utronix.de" <tglx@...utronix.de>,
	"shradhagupta@...ux.microsoft.com" <shradhagupta@...ux.microsoft.com>,
	"andrew+netdev@...n.ch" <andrew+netdev@...n.ch>, Konstantin Taranov
	<kotaranov@...rosoft.com>, "horms@...nel.org" <horms@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next,v7] net: mana: Add handler for hardware servicing
 events



> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Thursday, June 12, 2025 9:22 PM
> To: Haiyang Zhang <haiyangz@...ux.microsoft.com>
> Cc: linux-hyperv@...r.kernel.org; netdev@...r.kernel.org; Haiyang Zhang
> <haiyangz@...rosoft.com>; Dexuan Cui <decui@...rosoft.com>;
> stephen@...workplumber.org; KY Srinivasan <kys@...rosoft.com>; Paul
> Rosswurm <paulros@...rosoft.com>; olaf@...fle.de; vkuznets@...hat.com;
> davem@...emloft.net; wei.liu@...nel.org; edumazet@...gle.com;
> pabeni@...hat.com; leon@...nel.org; Long Li <longli@...rosoft.com>;
> ssengar@...ux.microsoft.com; linux-rdma@...r.kernel.org;
> daniel@...earbox.net; john.fastabend@...il.com; bpf@...r.kernel.org;
> ast@...nel.org; hawk@...nel.org; tglx@...utronix.de;
> shradhagupta@...ux.microsoft.com; andrew+netdev@...n.ch; Konstantin
> Taranov <kotaranov@...rosoft.com>; horms@...nel.org; linux-
> kernel@...r.kernel.org
> Subject: [EXTERNAL] Re: [PATCH net-next,v7] net: mana: Add handler for
> hardware servicing events
> 
> On Tue, 10 Jun 2025 11:42:22 -0700 Haiyang Zhang wrote:
> > v6:
> > Not acquiring module refcnt as suggested by Paolo Abeni.
> 
> TBH I'm not 100% sure this is correct.
> If the service worker operations end up unbinding the driver from
> the device holding the device ref may not prevent the module from
> being unloaded.
> 
> Could you try to trigger that condition? Make that msleep() in the work
> even longer and try to remove the module while the work is sleeping
> there?

Thanks for your suggestion! I tested and found that I can rmmod mana 
during the sleep and caused accessing freed memory. And getting the extra 
module refcnt fixed this (prevented rmmod during sleep). So, I added back
the module refcnt holding, and submitted v8.

Thanks,
- Haiyang