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From: Andrew Lunn <andrew@lunn.ch>
To: Arun Ramadoss <arun.ramadoss@microchip.com>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	George McCollister <george.mccollister@gmail.com>,
	Jakub Kicinski <kuba@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Vladimir Oltean <olteanv@gmail.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	UNGLinuxDriver@microchip.com,
	Woojung Huh <woojung.huh@microchip.com>
Subject: Re: [PATCH net] net: dsa: microchip: Added the condition for scheduling ksz_mib_read_work
Date: Fri, 8 Oct 2021 15:58:16 +0200	[thread overview]
Message-ID: <YWBOeP3dHFbEdg8w@lunn.ch> (raw)
In-Reply-To: <20211008084348.7306-1-arun.ramadoss@microchip.com>

On Fri, Oct 08, 2021 at 02:13:48PM +0530, Arun Ramadoss wrote:
> When the ksz module is installed and removed using rmmod, kernel crashes
> with null pointer dereferrence error. During rmmod, ksz_switch_remove
> function tries to cancel the mib_read_workqueue using
> cancel_delayed_work_sync routine.
> 
> At the end of  mib_read_workqueue execution, it again reschedule the
> workqueue unconditionally. Due to which queue rescheduled after
> mib_interval, during this execution it tries to access dp->slave. But
> the slave is unregistered in the ksz_switch_remove function. Hence
> kernel crashes.

Something not correct here.

https://www.kernel.org/doc/html/latest/core-api/workqueue.html?highlight=delayed_work#c.cancel_delayed_work_sync

This is cancel_work_sync() for delayed works.

and

https://www.kernel.org/doc/html/latest/core-api/workqueue.html?highlight=delayed_work#c.cancel_work_sync

This function can be used even if the work re-queues itself or
migrates to another workqueue.

Maybe the real problem is a missing call to destroy_worker()?

      Andrew

  reply	other threads:[~2021-10-08 13:58 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-08  8:43 [PATCH net] net: dsa: microchip: Added the condition for scheduling ksz_mib_read_work Arun Ramadoss
2021-10-08 13:58 ` Andrew Lunn [this message]
2021-10-08 18:34   ` Jakub Kicinski
2021-10-11  9:41     ` Arun.Ramadoss
2021-10-11 13:45       ` Jakub Kicinski

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