On Tue, Feb 13, 2007 at 02:32:43PM -0800, David Miller wrote:
> From: Jay Vosburgh <[EMAIL PROTECTED]>
> Date: Tue, 13 Feb 2007 14:26:28 -0800
>
> > In reference to Andy's recent patch (which first did conditional
> > locking for rtnl, then later acquired rtnl for every entry into the
> > timer function), I know the conditional locking isn't popular, but it
> > seems to me that it's a less bad alternative than holding rtnl every
> > time the bond_mii_monitor() runs (typically 10 - 50 times per second).
> > Or is the rtnl lock really so cheap that this isn't an issue? The
> > overwhelming majority of cases the mii_monitor won't need to do anything
> > that requires rtnl, so only holding it when needed is better.
>
> We definitely don't want to take the RTNL that often if it can
> be avoided.
>
> Maybe if you put the RTNL acquisition deeper into the call
> path, ie. down into the code that knows RTNL is needed,
> perhaps it won't be so ugly. Replace the conditions with
> functions.
That is almost exactly what I am working on right now. I'm trying to
determine where the best place to put this would be so reduce the
chance that I'd be using conditional locking.
I once put together a patch that used a macro like this (ignore the
whitespace problems, this was just a cut and paste):
/**
* bond_rtnl_wrapper - take the rtnl_lock if needed
* @x: function with args
*
*/
#define RTNL_WRAPPER(x) \
({ \
int __rc__; \
if (rtnl_trylock()) { \
__rc__ = x; \
rtnl_unlock(); \
} else { \
__rc__ = x; \
} \
__rc__; \
})
and wrapped it around the calls to dev_set_mac_address. I wasn't
pleased with it, but it seemed like it worked pretty well based on the
testing I did.
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
