Subject: Re: [RFC net-next PATCH V1 9/9] net: frag remove readers-writer lock (hack)

From: Stephen Hemminger <[email-masked]>
Date: Sun, 25 Nov 2012 22:03:16 -0800

On Fri, 23 Nov 2012 14:08:47 +0100
Jesper Dangaard Brouer <[email-masked]> wrote:

> Do NOT APPLY this patch.
> 
> After all the other patches, the rw_lock is now the contention point.

Reader-writer locks are significantly slower than a simple spinlock.
Unless the reader holds the lock for "significant" number of cycles,
a spin lock will be faster. 

Did you try just changing it to a spinlock?