Messages in this thread | | | Date | Wed, 30 Oct 2013 13:48:39 -0700 | From | Andrew Morton <> | Subject | Re: [RFC PATCH -next] Fix printk_once build errors due to __read_mostly |
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On Wed, 30 Oct 2013 10:18:21 +0000 James Hogan <james.hogan@imgtec.com> wrote:
> Commit 3e39c1ab04ba (printk: mark printk_once test variable > __read_mostly) added __read_mostly to the __print_once bool in the > printk_once() macro, but __read_mostly is defined in <linux/cache.h> > which isn't included from <linux/printk.h>. This results in build errors > like this: > > arch/metag/mm/l2cache.c: In function 'meta_l2c_setup': > arch/metag/mm/l2cache.c:56: error: '__read_mostly' undeclared > > This is fixed by adding an include of <linux/cache.h> from > <linux/printk.h> since I don't think printk_once() users should need to > include <linux/cache.h> for it to work. > > Note that this actually adds a recursive include, since <linux/cache.h> > includes <linux/kernel.h>, which includes <linux/printk.h>. The actual > dependencies are all in macros so it doesn't actually seem to result in > any build failures, but it's clearly less than ideal.
Yitch.
> Signed-off-by: James Hogan <james.hogan@imgtec.com> > Cc: Joe Perches <joe@perches.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: linux-metag@vger.kernel.org > --- > This build failure was caught in today's linux-next. > > I'm not too keen on this due to the recursive include. Is it better to > just workaround the problem by including <linux/cache.h> from the .c > file that fails to build, or should the original patch be removed > instead?
Well, these patches make the kernel worse. We should make it better, not worse.
One approach would be to add a new printk_once.h, which includes printk.h and cache.h.
I can't immediately think of a nice solution so I guess for now I'll drop printk-mark-printk_once-test-variable-__read_mostly.patch.
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