From: Måns Rullgård <m...@mansr.com> Date: Wed, 11 Nov 2015 19:17:07 +0000
> David Miller <da...@davemloft.net> writes: > >> From: Måns Rullgård <m...@mansr.com> >> Date: Wed, 11 Nov 2015 19:09:19 +0000 >> >>> David Miller <da...@davemloft.net> writes: >>> >>>> From: Måns Rullgård <m...@mansr.com> >>>> Date: Wed, 11 Nov 2015 18:25:05 +0000 >>>> >>>>> If the TX DMA channel is idle when start_xmit is called, it can be >>>>> started immediately. Checking the DMA status and starting it if >>>>> idle has to be done atomically somehow. >>>> >>>> ->ndo_start_xmit() is guaranteed to be invoked atomically, protected >>>> by the TX queue spinlock. >>> >>> Yes, but the DMA needs to be restarted from some other context if it was >>> busy when start_xmit checked. >> >> Then you can probably use the TXQ lock in the interrupt handler just for >> that. > > That seems a bit heavy-handed when the critical section for this is only > a tiny part of the start_xmit function. Then what synchornization primitive other than spin locks are you going to use for this? My point is that there is a spinlock the core code is _already_ taking, unconditionally, when ->ndo_start_xmit() executes. And you can therefore take advantage of that rather than using another lock of your own. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
