netdev - Re: [PATCH net-next V2] ptp: Avoid deadlocks in the programmable pin code.

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Message-Id: <20200330.111828.1385462054350886425.davem@davemloft.net>
Date:   Mon, 30 Mar 2020 11:18:28 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     richardcochran@...il.com
Cc:     netdev@...r.kernel.org, yangbo.lu@....com, vladimir.oltean@....com
Subject: Re: [PATCH net-next V2] ptp: Avoid deadlocks in the programmable
 pin code.

From: Richard Cochran <richardcochran@...il.com>
Date: Sun, 29 Mar 2020 07:55:10 -0700

> The PTP Hardware Clock (PHC) subsystem offers an API for configuring
> programmable pins.  User space sets or gets the settings using ioctls,
> and drivers verify dialed settings via a callback.  Drivers may also
> query pin settings by calling the ptp_find_pin() method.
> 
> Although the core subsystem protects concurrent access to the pin
> settings, the implementation places illogical restrictions on how
> drivers may call ptp_find_pin().  When enabling an auxiliary function
> via the .enable(on=1) callback, drivers may invoke the pin finding
> method, but when disabling with .enable(on=0) drivers are not
> permitted to do so.  With the exception of the mv88e6xxx, all of the
> PHC drivers do respect this restriction, but still the locking pattern
> is both confusing and unnecessary.
> 
> This patch changes the locking implementation to allow PHC drivers to
> freely call ptp_find_pin() from their .enable() and .verify()
> callbacks.
> 
> Signed-off-by: Richard Cochran <richardcochran@...il.com>
> Reported-by: Yangbo Lu <yangbo.lu@....com>
> Tested-by: Vladimir Oltean <vladimir.oltean@....com>

I made sure to apply v2 of this even though I just replied to v1
as if I had applied that one :-)