Subject: Re: [PATCH 1/4] Net device error logging, revised

From: Jim Keniston <[email-masked]>
Date: Tue, 26 Aug 2003 18:07:57 -0700

Jeff Garzik wrote:
> 
> Jim Keniston wrote:
> > #define netdev_printk(sevlevel, netdev, msglevel, format, arg...)     \
> > do {                                                                  \
> > if (NETIF_MSG_##msglevel == NETIF_MSG_ALL || ((netdev)->msg_enable & NETIF_MSG_##msglevel)) { \
> >       char pfx[40];                                                   \
> >       printk(sevlevel "%s: " format , make_netdev_msg_prefix(pfx, netdev) , ## arg);  \
> > }} while (0)
> >
> > This would make your code bigger, but not that much bigger for the common case where
> > the msglevel is omitted (and the 'if(...)' is optimized out).
> 
> "NETIF_MSG_" is silly and should be eliminated.

>>From this, I infer that you think that the option to "omit" the msglevel arg --
e.g.,
	netdev_err(dev,, "NIC is fried!\n");	/* always logged */
-- is silly.  No big deal.  Its sole purpose is to help keep netdev_* calls terse.

> A separate "NETIF_MSG_ALL" test is not needed, because msg_enable is a
> bitmask.  A msg_enable of 0xffffffff will naturally create a NETIF_MSG_ALL.

But how do you code a netdev_* call where you ALWAYS want the message (including
netdev_printk-style prefix) logged, regardless of the value of msg_enable?  That's
what NETIF_MSG_ALL is for (and why it might be better called NETIF_MSG_ALWAYS)...
	netdev_err(dev, ALL, "NIC is fried!\n");	/* always logged */
or
	netdev_err(dev, ALWAYS, "NIC is fried!\n");	/* always logged */

> 
> Also, whatever mechanism is created, it needs to preserve the feature of
> the existing system:
> 
>         if (a quick bitmask test)
>                 do something
> 
> And preferably "do something" is not inlined, because printk'ing --
> although it may appear in a fast path during debugging -- cannot be
> considered a fast path itself.
> 
>         Jeff

Sorry, I'm not sure what you're getting at here.  netdev_* doesn't prevent
people from using the existing netif_msg_* macros; it just provides shorthand
for the (usual) case where "do something" is "printk".

Jim