linux-kernel - Re: [RFC PATCH] net: phy: Don't miss phy_suspend() on PHY

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 16 Mar 2017 09:46:49 +0200
From:   Roger Quadros <rogerq@...com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     <f.fainelli@...il.com>, <davem@...emloft.net>,
        <kyle.roeschley@...com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] net: phy: Don't miss phy_suspend() on PHY_HALTED for
 PHYs with interrupts

On 15/03/17 17:49, Andrew Lunn wrote:
> On Wed, Mar 15, 2017 at 05:00:08PM +0200, Roger Quadros wrote:
>> Andrew,
>>
>> On 15/03/17 16:08, Andrew Lunn wrote:
>>> On Wed, Mar 15, 2017 at 03:51:27PM +0200, Roger Quadros wrote:
>>>> Since commit 3c293f4e08b5 ("net: phy: Trigger state machine on state change and not polling.")
>>>> phy_suspend() doesn't get called as part of phy_stop() for PHYs using
>>>> interrupts because the phy state machine is never triggered after a phy_stop().
>>>>
>>>> Explicitly trigger the PHY state machine so that it can
>>>> see the new PHY state (HALTED) and suspend the PHY.
>>>>
>>>> Signed-off-by: Roger Quadros <rogerq@...com>
>>>
>>> Hi Roger
>>>
>>> This seems sensible. It mirrors what phy_start() does.
>>>
>>> Reviewed-by: Andrew Lunn <andrew@...n.ch>
>>
>> The reason for this being an RFC was the following comment just before
>> where I add the phy_trigger_machine()
>>
>>         /* Cannot call flush_scheduled_work() here as desired because
>>          * of rtnl_lock(), but PHY_HALTED shall guarantee phy_change()
>>          * will not reenable interrupts.
>>          */
>>
>> Is this comment still applicable? If yes, is it OK to call
>> phy_trigger_machine() there?
> 
> Humm, good question.
> 
> My _guess_ would be, calling it with sync=True could
> deadlock. sync=False is probably safe. But lets see what Florian says.

I agree that we should use phy_trigger_machine() with sync=False.

> 
>>
>>>
>>> It does however lead to a follow up question. Are there other places
>>> phydev->state is changed and it is missing a phy_trigger_machine()?
>>>
>>
>> One other place I think we should add phy_trigger_machine() is phy_start_aneg().
> 
> Humm, that might get us into a tight loop.
> 
> phy_start_aneg() kicks the phy driver to start autoneg and sets
> phydev->state = PHY_AN.
> 
> phy_trigger_machine() triggers the state machine immediately. 
> 
> In state PHY_AN, we check if aneg is done. If not, it sets needs_aneg
> = true. At the end of the state machine, this then calls
> phy_start_aneg(), and it all starts again.
> 
> We are missing the 1s delay we have with polling. So for
> phy_start_aneg(), we might need a phy_delayed_trigger_machine(), which
> waits a second before doing anything?

I think that should do the trick.

How about this?

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 8fef03b..162061c 100644
--- a/drivers/net/phy/phy.c
+++ b/drivers/net/phy/phy.c
@@ -630,6 +630,10 @@ int phy_start_aneg(struct phy_device *phydev)
 
 out_unlock:
 	mutex_unlock(&phydev->lock);
+
+	if (!err)
+		queue_delayed_work(system_power_efficient_wq, &phydev->state_queue, HZ);
+
 	return err;
 }
 EXPORT_SYMBOL(phy_start_aneg);

-- 
cheers,
-roger