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Date: Fri, 16 Jan 2015 16:32:03 +0000 From: Patrick McHardy <kaber@...sh.net> To: Thomas Graf <tgraf@...g.ch> Cc: davem@...emloft.net, netdev@...r.kernel.org, kernel@...r.kernel.org, herbert@...dor.apana.org.au, paulmck@...ux.vnet.ibm.com, edumazet@...gle.com, john.r.fastabend@...el.com, josh@...htriplett.org, netfilter-devel@...r.kernel.org Subject: Re: [PATCH 7/9] rhashtable: Per bucket locks & deferred expansion/shrinking On 16.01, Thomas Graf wrote: > On 01/16/15 at 04:03pm, Patrick McHardy wrote: > > On 16.01, Thomas Graf wrote: > > > A walker may not see insertions that occur after the walker was started > > > if resizing is enabled. Is that a problem for nftables? > > > > No, that would be Ok. The case I'm wondering about is: > > > > - insertion > > - resize starts > > - another insertion > > - walker, resize not finished yet > > Correct, walker may not see "another insertion". The window for this > behavior to occur is not the full resize operation, just the linking > period, but it may occur. The length of the window is typically > equal to a grace period. > > We can provide a synchronization function to block the dumper or the > insertion/removal until the linking is complete. The latter would > give the old runtime behaviour back (variable runtime of insert), > the blocked dumper might be preferred. What do you think? If we have to block, the dumper if of course preferred. Taking the mutex should do fine I guess? I suppose walking both tables without any races would be rather complicated. -- 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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