netdev - Re: [RFC net-next 2/2] net: net-sysfs: Reduce netstat_show read

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Date:   Tue, 10 Apr 2018 13:17:26 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     saeedm@...lanox.com
Cc:     netdev@...r.kernel.org
Subject: Re: [RFC net-next 2/2] net: net-sysfs: Reduce netstat_show
 read_lock critical section

From: Saeed Mahameed <saeedm@...lanox.com>
Date: Tue, 10 Apr 2018 10:08:12 -0700

> Instead of holding the device chain read_lock also while calling
> dev_get_stats just hold it only to check dev_isalive, if the dev is alive,
> hold that dev via dev_hold then release the read_lock.
> 
> When done handling the device, dev_put it.
> 
> Signed-off-by: Saeed Mahameed <saeedm@...lanox.com>

My feedback here is that same as for patch #1.

Two atomics for a shorter RCU lock hold time is not that great of
a tradeoff.