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Date: Mon, 20 Jan 2020 09:29:14 +0100 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: Finn Thain <fthain@...egraphics.com.au> Cc: "David S. Miller" <davem@...emloft.net>, Thomas Bogendoerfer <tsbogend@...ha.franken.de>, Chris Zankel <chris@...kel.net>, Laurent Vivier <laurent@...ier.eu>, netdev <netdev@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: [PATCH net 04/19] net/sonic: Add mutual exclusion for accessing shared state Hi Finn, On Mon, Jan 20, 2020 at 12:19 AM Finn Thain <fthain@...egraphics.com.au> wrote: > The netif_stop_queue() call in sonic_send_packet() races with the > netif_wake_queue() call in sonic_interrupt(). This causes issues > like "NETDEV WATCHDOG: eth0 (macsonic): transmit queue 0 timed out". > Fix this by disabling interrupts when accessing tx_skb[] and next_tx. > Update a comment to clarify the synchronization properties. > > Fixes: efcce839360f ("[PATCH] macsonic/jazzsonic network drivers update") > Tested-by: Stan Johnson <userm57@...oo.com> > Signed-off-by: Finn Thain <fthain@...egraphics.com.au> Thanks for your patch! > --- a/drivers/net/ethernet/natsemi/sonic.c > +++ b/drivers/net/ethernet/natsemi/sonic.c > @@ -242,7 +242,7 @@ static void sonic_tx_timeout(struct net_device *dev) > * wake the tx queue > * Concurrently with all of this, the SONIC is potentially writing to > * the status flags of the TDs. > - * Until some mutual exclusion is added, this code will not work with SMP. However, > + * A spin lock is needed to make this work on SMP platforms. However, > * MIPS Jazz machines and m68k Macs were all uni-processor machines. > */ > > @@ -252,6 +252,7 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev) > dma_addr_t laddr; > int length; > int entry; > + unsigned long flags; > > netif_dbg(lp, tx_queued, dev, "%s: skb=%p\n", __func__, skb); > > @@ -273,6 +274,8 @@ static int sonic_send_packet(struct sk_buff *skb, struct net_device *dev) > return NETDEV_TX_OK; > } > > + local_irq_save(flags); > + Wouldn't it be better to use a spinlock instead? It looks like all currently supported platforms (Mac, Jazz, and XT2000) do no support SMP, but I'm not 100% sure about the latter. And this generic sonic.c core may end up being used on other platforms that do support SMP. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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