Messages in this thread | | | Date | Thu, 6 Sep 2012 16:52:45 +0200 | From | Nicolas Ferre <> | Subject | Re: [PATCH 04/10] net/macb: Fix a race in macb_start_xmit() |
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On 09/05/2012 11:30 PM, David Miller : > From: Nicolas Ferre <nicolas.ferre@atmel.com> > Date: Wed, 5 Sep 2012 10:19:11 +0200 > >> From: Havard Skinnemoen <havard@skinnemoen.net> >> >> Fix a race in macb_start_xmit() where we unconditionally set the TSTART bit. >> If an underrun just happened (we do this with interrupts disabled, so it might >> not have been handled yet), the controller starts transmitting from the first >> entry in the ring, which is usually wrong. >> Restart the controller after error handling. >> >> Signed-off-by: Havard Skinnemoen <havard@skinnemoen.net> >> [nicolas.ferre@atmel.com: split patch in topics] >> Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com> > > Accumulating special case code and checks into the hot path of TX packet > processing is extremely unwise. > > Instead, when you handle the TX error conditions and reset the chip you > should first ensure that there are no flows of control in the transmit > function of your driver by using the appropriate locking et al. facilities. > > For example, you can quiesce the transmit path by handling the chip error > interrupt as follows: > > 1) Disable chip interrupt generation. > > 2) Schedule a workqueue so you can process the reset outside of hard > interrupt context. > > 3) In the workqueue function, disable NAPI and perform a > netif_tx_disable() to guarentee there are no threads of > execution trying to queue up packets for TX into the driver. > > 4) Perform your chip reset and whatever else is necessary. > > 5) Re-enable NAPI and TX. > > Then you don't need any special checks in your xmit method at all.
I see... I will rework the series and try to implement this as part of the "[PATCH 06/10] net/macb: better manage tx errors"
So this patch will disappear in future v2 series and patch 06 will be seriously modified. In fact I will also try to stack "cosmetic" patches at the beginning of the series.
Thanks, best regards, -- Nicolas Ferre
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