Messages in this thread | | | Date | Thu, 1 Oct 2009 20:19:20 +0200 | From | Uwe Kleine-König <> | Subject | Re: [PATCH 31/34] move virtrng_remove to .devexit.text |
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Hello Michael,
On Thu, Oct 01, 2009 at 08:05:00PM +0200, Michael S. Tsirkin wrote: > On Thu, Oct 01, 2009 at 07:41:16PM +0200, Uwe Kleine-König wrote: > > Hello Michael, > > > > > > But note it's not an error in general to use a .text function as remove > > > > callback. E.g. take drivers/gpio/twl4030-gpio.c. gpio_twl4030_remove > > > > is used in gpio_twl4030_probe which is defined using __devinit. So > > > > using __devexit for gpio_twl4030_remove is wrong. (So there is a bug, > > > > as gpio_twl4030_remove uses __devexit.) I didn't try, but as far as I > > > > understand this will result in a compile error if the driver is built-in > > > > with HOTPLUG=n. > > > > > > Wait a second. > > > As far as I understand, __devexit makes it possible to remove code if > > > hotplug is off. > > right. > > > > > At least for static functions, it's enough to mark their only use > > > as _devexit_p, and compiler will remove the text as it's unused. > > > > > > Isn't that right? > > hmm, I don't know. I'll try, one moment. OK, you're right. The > > function is discarded with a compiler warning. > > > > > If so, what, again, was the motivation for the patches that added > > > __devexit to functions that were already used with __devexit_p? > > I thought it saves some memory, but as it looks now it only fixes a > > compiler warning. > > We can redefine __devexit_p(x) to something like > #define __devexit_p(x) ((typeof(x) *)NULL) > and this will shut down the warning without need to fix the code. Mmmmh, don't know. A definitive advantage is that there is only a single point in the code that defines if a function is discarded or not. Nothing that needs to be consistent. For me it feels somehow wrong anyhow, but that might be only because I'm used to the current model.
> > Note there are two types of errors fixed in this series. One is: > > > > -static int func(void arg) > > +static int __devexit func(void arg) > > > > if the only usage of func() is wraped by __devexit_p. This is (as > > seen above) not that critical, there is only a warning fixed. > > > > The other type results in a build failure: > > > > -remove = __devexit_p(another_func), > > +remove = __exit_p(another_func), > > > > with another_func being defined using __exit. In the case > > defined(MODULE) && defined(CONFIG_HOTPLUG) another_func is discarded, > > but __devexit_p(another_func) evaluates to another_func and thus the > > module doesn't link. > > Yes, calling __exit function from non- __exit is always a bug. > I think there's a make flag to warn about this, not sure why it's > not the default. I think it was disabled because there were too many warnings :-)
Best regards Uwe
-- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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