netdev - netif_poll_enable() & barrier

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Message-Id: <1166586252.19254.118.camel@localhost.localdomain>
Date:	Wed, 20 Dec 2006 14:44:12 +1100
From:	Benjamin Herrenschmidt <benh@....ibm.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	Linux Kernel list <linux-kernel@...r.kernel.org>,
	netdev@...r.kernel.org
Subject: netif_poll_enable() & barrier

Hi !

I stumbled accross what might be a bug on out of order architecture:

netif_poll_enable() only does a clear_bit(). However,
netif_poll_disable/enable pairs are often used as simili-spinlocks.

(netif_poll_enable() has pretty much spin_lock semantics except that it
schedules instead of looping).

Thus, shouldn't netif_poll_disable() do an smp_wmb(); before clearing
the bit to make sure that any stores done within the poll-disabled
section are properly visible to the rest of the system before clearing
the bit ?

Cheers,
Ben.

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