netdev - Re: Printing the driver name as part of the netdev watchdog message

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Message-ID: <adafxqlxqi5.fsf@cisco.com>
Date:	Mon, 07 Jul 2008 15:45:38 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	David Miller <davem@...emloft.net>
Cc:	shemminger@...tta.com, arjan@...radead.org, netdev@...r.kernel.org
Subject: Re: Printing the driver name as part of the netdev watchdog message

 > > For consistency each call through ethtool_ops should
 > > be holding rtnl mutex. And since dev_watchdog is a timer routine,
 > > it is not safe to acquire a mutex there.
 > 
 > I think "get driver info", which does nothing but copy strings out of
 > the driver software state, is a safe exception to these strict locking
 > rules.

it seems that's not universally the case, eg get_drvinfo() in
drivers/net/cxgb3/cxgb3_main.c does

	t3_get_fw_version(adapter, &fw_vers);
	t3_get_tp_version(adapter, &tp_vers);

and from reading further in the code it's not obvious that this is safe
to do without serialization (it calls into t3_read_flash(), which does a
typical "write address reg, read data reg" sequence to access flash,
without any locking).

 - R.
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