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Message-ID: <1398349249.29914.67.camel@edumazet-glaptop2.roam.corp.google.com> Date: Thu, 24 Apr 2014 07:20:49 -0700 From: Eric Dumazet <eric.dumazet@...il.com> To: Chris Mason <clm@...com> Cc: netdev@...r.kernel.org Subject: Re: [PATCH RFC] ipv6_fib limit spinlock hold times for /proc/net/ipv6_route On Thu, 2014-04-24 at 09:59 -0400, Chris Mason wrote: > The ipv6 code to dump routes in /proc/net/ipv6_route can hold > a read lock on the table for a very long time. This ends up blocking > writers and triggering softlockups. > > This patch is a simple work around to limit the number of entries > we'll walk while processing /proc/net/ipv6_route. It intentionally > slows down proc file reading to make sure we don't lock out the > real ipv6 traffic. > > This patch is also horrible, and doesn't actually fix the entire > problem. We still have rcu_read_lock held the whole time we cat > /proc/net/ipv6_route. On an unpatched machine, I've clocked the > time required to cat /proc/net/ipv6_route at 14 minutes. > > java cats this proc file on startup to search for local routes, and the > resulting contention on the table lock makes our boxes fall over. > > So, I'm sending the partial fix to get discussion started. > > Signed-off-by: Chris Mason <clm@...com> > > --- It might be time to convert this to RCU and/or a better data structure. -- 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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