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Date: Tue, 6 Mar 2012 14:17:45 +0000 From: Russell King - ARM Linux <linux@....linux.org.uk> To: Ben Hutchings <bhutchings@...arflare.com> Cc: Roland Stigge <stigge@...com.de>, alexander.h.duyck@...el.com, baruch@...s.co.il, ian.campbell@...rix.com, arnd@...db.de, netdev@...r.kernel.org, eilong@...adcom.com, kevin.wells@....com, w.sang@...gutronix.de, jeffrey.t.kirsher@...el.com, joe@...ches.com, davem@...emloft.net, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org Subject: Re: [PATCH v4] lpc32xx: Added ethernet driver: smp_wmb() On Tue, Mar 06, 2012 at 02:03:28PM +0000, Ben Hutchings wrote: > On Tue, 2012-03-06 at 11:43 +0100, Roland Stigge wrote: > > On 03/05/2012 11:45 PM, Ben Hutchings wrote: > > >> + /* Clear and enable interrupts */ > > >> + writel(0xFFFF, LPC_ENET_INTCLEAR(pldat->net_base)); > > >> + lpc_eth_enable_int(pldat->net_base); > > >> + > > >> + /* Get the next TX buffer output index */ > > >> + pldat->num_used_tx_buffs = 0; > > >> + pldat->last_tx_idx = > > >> + readl(LPC_ENET_TXCONSUMEINDEX(pldat->net_base)); > > > > > > Doesn't this need to be done *before* enabling interrupts? Also, I > > > think you need an smp_wmb() so that the interrupt handler is guaranteed > > > to see all these writes. > > > > Do you mean _one_ smp_wmb() directly after lpc_eth_enable_int() (which > > I'm moving behind the above code? > > The sequence should be > > pldat->state = values...; > smp_wmb(); > enable_interrupts(); Is this correct? "SMP BARRIER PAIRING" and "EXAMPLES OF MEMORY BARRIER SEQUENCES" in Documentation/memory-barriers.txt suggest that there should be some kind of pairing with smp_wmb() to ensure correctness. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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