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Date: Mon, 17 Feb 2020 10:20:06 +0100 From: Alexandre Belloni <alexandre.belloni@...tlin.com> To: Horatiu Vultur <horatiu.vultur@...rochip.com> Cc: UNGLinuxDriver@...rochip.com, davem@...emloft.net, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] net: mscc: fix in frame extraction On 17/02/2020 09:31:33+0100, Horatiu Vultur wrote: > Each extracted frame on Ocelot has an IFH. The frame and IFH are extracted > by reading chuncks of 4 bytes from a register. > > In case the IFH and frames were read corretly it would try to read the next > frame. In case there are no more frames in the queue, it checks if there > were any previous errors and in that case clear the queue. But this check > will always succeed also when there are no errors. Because when extracting > the IFH the error is checked against 4(number of bytes read) and then the > error is set only if the extraction of the frame failed. So in a happy case > where there are no errors the err variable is still 4. So it could be > a case where after the check that there are no more frames in the queue, a > frame will arrive in the queue but because the error is not reseted, it > would try to flush the queue. So the frame will be lost. > > The fix consist in resetting the error after reading the IFH. > > Signed-off-by: Horatiu Vultur <horatiu.vultur@...rochip.com> Acked-by: Alexandre Belloni <alexandre.belloni@...tlin.com> > --- > drivers/net/ethernet/mscc/ocelot_board.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/net/ethernet/mscc/ocelot_board.c b/drivers/net/ethernet/mscc/ocelot_board.c > index b38820849faa..1135a18019c7 100644 > --- a/drivers/net/ethernet/mscc/ocelot_board.c > +++ b/drivers/net/ethernet/mscc/ocelot_board.c > @@ -114,6 +114,14 @@ static irqreturn_t ocelot_xtr_irq_handler(int irq, void *arg) > if (err != 4) > break; > > + /* At this point the IFH was read correctly, so it is safe to > + * presume that there is no error. The err needs to be reset > + * otherwise a frame could come in CPU queue between the while > + * condition and the check for error later on. And in that case > + * the new frame is just removed and not processed. > + */ > + err = 0; > + > ocelot_parse_ifh(ifh, &info); > > ocelot_port = ocelot->ports[info.port]; > -- > 2.17.1 > -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
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