netdev - RE: [PATCH iwl-net 2/3] ice: Don't process extts if PTP is disabled

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Message-ID: <CO1PR11MB50893FB1F17FA83018D85B9ED6DA2@CO1PR11MB5089.namprd11.prod.outlook.com>
Date: Mon, 8 Jul 2024 22:50:53 +0000
From: "Keller, Jacob E" <jacob.e.keller@...el.com>
To: Simon Horman <horms@...nel.org>, "Kolacinski, Karol"
	<karol.kolacinski@...el.com>
CC: "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, "Nguyen, Anthony L"
	<anthony.l.nguyen@...el.com>, "Kitszel, Przemyslaw"
	<przemyslaw.kitszel@...el.com>
Subject: RE: [PATCH iwl-net 2/3] ice: Don't process extts if PTP is disabled



> -----Original Message-----
> From: Simon Horman <horms@...nel.org>
> Sent: Wednesday, June 19, 2024 9:41 AM
> To: Kolacinski, Karol <karol.kolacinski@...el.com>
> Cc: intel-wired-lan@...ts.osuosl.org; netdev@...r.kernel.org; Nguyen, Anthony L
> <anthony.l.nguyen@...el.com>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@...el.com>; Keller, Jacob E <jacob.e.keller@...el.com>
> Subject: Re: [PATCH iwl-net 2/3] ice: Don't process extts if PTP is disabled
> 
> On Tue, Jun 18, 2024 at 12:41:37PM +0200, Karol Kolacinski wrote:
> > From: Jacob Keller <jacob.e.keller@...el.com>
> >
> > The ice_ptp_extts_event() function can race with ice_ptp_release() and
> > result in a NULL pointer dereference which leads to a kernel panic.
> >
> > Panic occurs because the ice_ptp_extts_event() function calls
> > ptp_clock_event() with a NULL pointer. The ice driver has already
> > released the PTP clock by the time the interrupt for the next external
> > timestamp event occurs.
> >
> > To fix this, modify the ice_ptp_extts_event() function to check the
> > PTP state and bail early if PTP is not ready. To ensure that the IRQ
> > sees the state change, call synchronize_irq() before removing the PTP
> > clock.
> 
> Hi Karol and Jacob,
> 
> After pf->ptp.state is set in ptp_clock_event(),
> ice_ptp_disable_all_extts() is called which in turn calls
> synchronize_irq(). Which I assume is what the last sentence above refers
> to. But the way it is worded it sounds like a call to synchronize_irq() is
> being added by this patch, which is not the case.
> 
> I suppose it is not a big deal, but this did confuse me.
> So perhaps the wording could be enhanced?
> 

I believe the call to synchronize_irq() predates this as the same IRQ is used for other timestamping/PTP related events.

This could be clarified in the commit message

> > Another potential fix would be to ensure that all the GPIO configuration
> > gets disabled during release of the driver. This is currently not
> > trivial as each device family has its own set of configuration which is
> > not shared across all devices. In addition, only some of the device
> > families use the pin configuration interface. For now, relying on the
> > state flag is the simpler solution.
> >
> > Fixes: 172db5f91d5f ("ice: add support for auxiliary input/output pins")
> > Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@...el.com>
> > Signed-off-by: Jacob Keller <jacob.e.keller@...el.com>
> > Signed-off-by: Karol Kolacinski <karol.kolacinski@...el.com>
> > ---
> >  drivers/net/ethernet/intel/ice/ice_ptp.c | 8 +++++---
> >  1 file changed, 5 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/intel/ice/ice_ptp.c
> b/drivers/net/ethernet/intel/ice/ice_ptp.c
> > index 30f1f910e6d9..b952cad42f92 100644
> > --- a/drivers/net/ethernet/intel/ice/ice_ptp.c
> > +++ b/drivers/net/ethernet/intel/ice/ice_ptp.c
> > @@ -1559,6 +1559,10 @@ void ice_ptp_extts_event(struct ice_pf *pf)
> >  	u8 chan, tmr_idx;
> >  	u32 hi, lo;
> >
> > +	/* Don't process timestamp events if PTP is not ready */
> > +	if (pf->ptp.state != ICE_PTP_READY)
> > +		return;
> > +
> >  	tmr_idx = hw->func_caps.ts_func_info.tmr_index_owned;
> >  	/* Event time is captured by one of the two matched registers
> >  	 *      GLTSYN_EVNT_L: 32 LSB of sampled time event
> > @@ -1573,10 +1577,8 @@ void ice_ptp_extts_event(struct ice_pf *pf)
> >  			event.timestamp = (((u64)hi) << 32) | lo;
> >  			event.type = PTP_CLOCK_EXTTS;
> >  			event.index = chan;
> > -
> > -			/* Fire event */
> > -			ptp_clock_event(pf->ptp.clock, &event);
> >  			pf->ptp.ext_ts_irq &= ~(1 << chan);
> > +			ptp_clock_event(pf->ptp.clock, &event);
> >  		}
> >  	}
> >  }
> 
> I'm also confused (often, TBH!) as to how the last hunk of this
> patch relates to the problem at hand.