Messages in this thread | | | Date | Mon, 05 May 2014 16:56:53 -0400 (EDT) | Subject | Re: [PATCH 5/5] net: macb: Fix race between HW and driver | From | David Miller <> |
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From: Soren Brinkmann <soren.brinkmann@xilinx.com> Date: Sun, 4 May 2014 15:43:02 -0700
> Under "heavy" RX load, the driver cannot handle the descriptors fast > enough. In detail, when a descriptor is consumed, its used flag is > cleared and once the RX budget is consumed all descriptors with a > cleared used flag are prepared to receive more data. Under load though, > the HW may constantly receive more data and use those descriptors with a > cleared used flag before they are actually prepared for next usage. > > The head and tail pointers into the RX-ring should always be valid and > we can omit clearing and checking of the used flag. > > Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Isn't the RX_USED bit the only thing that controls what RX entries the chip will try to use?
I can't see how you can just remove the RX_USED bit handling altogether.
The problem actually seems to be that in the current code we clear the RX_USED bit before we actually reallocate the buffer and set it up.
It should be a bug to see the RX_USED bit set in gem_rx_refill(), and the only reason why it can happen is exactly because you're clearing it too early in gem_rx().
This change doesn't seem to be correct, I'm not applying this series sorry.
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