PERFORCE change 112835 for review
Hans Petter Selasky
hselasky at c2i.net
Sun Jan 14 02:25:39 UTC 2007
On Saturday 13 January 2007 20:29, M. Warner Losh wrote:
> In message: <200701122132.l0CLWuAG096027 at repoman.freebsd.org>
>
> Hans Petter Selasky <hselasky at freebsd.org> writes:
> : http://perforce.freebsd.org/chv.cgi?CH=112835
> :
> : Change 112835 by hselasky at hselasky_mini_itx on 2007/01/12 21:32:24
> :
> : ether_ifattach() must be called without any mutexes held, hence
> : it can sleep. Use generated typedef's for prototypes for exported
> : device methods. This prevents invalid parameter passing and return.
>
> Why do the attach methods even have locked mutexes to drop? That was
> a common error in the early locking efforts that too many network
> drivers inherited. Maybe the right fix is to just remove the
> lock/unlock pairs in attach entirely...
>
The attach code in question is run from a separate config thread, which by
default locks "sc->sc_mtx" before calling the callback function. Therefore
the code unlocks that lock, to avoid sleeping with mutex locked errors.
Probably all of the attach code can run without "sc->sc_mtx" locked, but will
require Giant locked, when changing the device tree, for example when adding
new child devices like MII-bus instances.
--HPS
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