netdev - Re: [PATCH net] net: dsa: microchip: Added the condition for scheduling ksz_mib_read

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Message-ID: <20211011064538.7fabf949@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 11 Oct 2021 06:45:38 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     <Arun.Ramadoss@...rochip.com>
Cc:     <andrew@...n.ch>, <olteanv@...il.com>,
        <linux-kernel@...r.kernel.org>, <george.mccollister@...il.com>,
        <vivien.didelot@...il.com>, <UNGLinuxDriver@...rochip.com>,
        <f.fainelli@...il.com>, <netdev@...r.kernel.org>,
        <Woojung.Huh@...rochip.com>, <davem@...emloft.net>
Subject: Re: [PATCH net] net: dsa: microchip: Added the condition for
 scheduling ksz_mib_read_work

On Mon, 11 Oct 2021 09:41:55 +0000 Arun.Ramadoss@...rochip.com wrote:
> On Fri, 2021-10-08 at 11:34 -0700, Jakub Kicinski wrote:
> > Also the cancel_delayed_work_sync() is suspiciously early in the
> > remove
> > flow. There is a schedule_work call in ksz_mac_link_down() which may
> > schedule the work back in. That'd also explain why the patch helps
> > since
> > ksz_mac_link_down() only schedules if (dev->mib_read_interval).  
> In this patch, I did two things. Added the if condition for
> rescheduling the queue and other is resetted the mib_read_interval to
> zero.
> As per the cancel_delayed_queue_sync() functionality, Now I tried rmod
> after removing the if condition for resheduling the queue,kernel didn't
> crash. So, concluded that it is not rearm in ksz_mib_read_work  is
> causing the problem but it is due to scheduling in the
> ksz_mac_link_down function. This function is called due to the
> dsa_unregister_switch. Due to resetting of the mib_read_interval to
> zero in switch_remove, the queue is not scheduled in mac_link_down, so
> kernel didn't crash.
> 
> And also, as per suggestion on cancel_delayed_work_sync() is
> suspiciously placed in switch_remove. I undo this patch, and tried just
> by moving the canceling of delayed_work after the dsa_unregister_switch
> function. As expected dsa_unregister_switch calls the
> ksz_mac_link_down, which schedules the mib_read_work. Now, when
> cancel_delayed_work_sync is called, it cancels all the workqueue. As a
> result, module is removed successfully without kernel crash.
> 
> Can I send the updated patch as v1 or new patch with updated commit
> message and description.

Please send a patch with just the second chunk (zeroing
mib_read_interval), you can mark it as v2.