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Date: Wed, 25 Jul 2012 10:43:36 -0400 From: Kevin Groeneveld <kgroeneveld@...il.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: netdev@...r.kernel.org Subject: Re: [PATCH] ppp: add 64 bit stats On Wed, Jul 25, 2012 at 12:04 AM, Eric Dumazet <eric.dumazet@...il.com> wrote: > It there are spinlocks already, why even adding u64_stats_sync ? That is a good question I have already wondered about myself. >include/linux/u64_stats_sync.h > >* 3) Write side must ensure mutual exclusion or one seqcount update could > * be lost, thus blocking readers forever. > * If this synchronization point is not a mutex, but a spinlock or > * spinlock_bh() or disable_bh() : It seems the u64_stats_sync requires some form of mutual exclusion. So why bother ever using it at all? Maybe there are cases where the required mutual exclusion can be cheaper than a spinlock? Maybe it is just to avoid the spinlocks on the read side of things? I hope you don't mind all my questions... -- 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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