On Mon, 29 Jun 2020 13:51:32 -0700 Andre Guedes wrote:
> > > @@ -435,6 +432,9 @@ static void igc_ptp_tx_hwtstamp(struct igc_adapter
> > > *adapter)
> > > struct igc_hw *hw = &adapter->hw;
> > > u64 regval;
> > >
> > > + if (WARN_ON_ONCE(!skb))
> > > + return;
> > > +
> > > regval = rd32(IGC_TXSTMPL);
> > > regval |= (u64)rd32(IGC_TXSTMPH) << 32;
> > > igc_ptp_systim_to_hwtstamp(adapter, &shhwtstamps, regval);
> > > @@ -466,7 +466,7 @@ static void igc_ptp_tx_work(struct work_struct *work)
> > > struct igc_hw *hw = &adapter->hw;
> > > u32 tsynctxctl;
> > >
> > > - if (!adapter->ptp_tx_skb)
> > > + if (!test_bit(__IGC_PTP_TX_IN_PROGRESS, &adapter->state))
> > > return;
> >
> > Not that reading ptp_tx_skb is particularly correct here, but I think
> > it's better. See how they get set:
> >
> > if (adapter->tstamp_config.tx_type == HWTSTAMP_TX_ON &&
> > !test_and_set_bit_lock(__IGC_PTP_TX_IN_PROGRESS,
> > &adapter->state)) {
> > skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
> > tx_flags |= IGC_TX_FLAGS_TSTAMP;
> >
> > adapter->ptp_tx_skb = skb_get(skb);
> > adapter->ptp_tx_start = jiffies;
> >
> > bit is set first and other fields after. Since there is no locking here
> > we may just see the bit but none of the fields set.
>
> I see your point, but note that the code within the if-block and the code in
> igc_ptp_tx_work() don't execute concurrently. adapter->ptp_tx_work is
> scheduled
> only on a time-sync interrupt, which is triggered if IGC_TX_FLAGS_TSTAMP is
> set (so adapter->ptp_tx_skb is valid).
What if timeout happens, igc_ptp_tx_hang() starts cleaning up and then
irq gets delivered half way through? Perhaps we should just add a spin
lock around the ptp_tx_s* fields?
