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    SubjectRe: [GIT PULL] core/locking changes for v3.1
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    Hi,

    On Mon, Jul 25, 2011 at 4:02 PM, Ingo Molnar <mingo@elte.hu> wrote:
    >
    > * Linus Torvalds <torvalds@linux-foundation.org> wrote:
    >
    >> On Mon, Jul 25, 2011 at 12:04 PM, Ingo Molnar <mingo@elte.hu> wrote:
    >> > ..
    >> > net/netfilter/nf_conntrack_core.c: In function ‘nf_conntrack_init’:
    >> > net/netfilter/nf_conntrack_core.c:1579:3: warning: the comparison
    >> > will always evaluate as ‘true’ for the address of
    >> > ‘nf_conntrack_attach’ will never be NULL [-Waddress]
    >>
    >> These all seem to be essentially compiler bugs.
    >>
    >> We have macros that do generic things (in this case
    >> "rcu_assign_pointer()" and tests their values. The fact that the tests
    >> sometimes end up being statically true (or false) is not something the
    >> compiler should complain about - it should use it to optimize the
    >> code.
    >>
    >> Sad.
    >>
    >> We can make a compiler bug-report, or disable -Waddress. Or maybe we
    >> can write the tests in a way that doesn't trigger the compiler bug.
    >>
    >> This same issue is why I hated -Wsign-compare. Some of the things
    >> gcc complained about were just technically moronic. So compiler
    >> warnings are not always a good thing.
    >
    > With -Wno-address added (see the first patch below) it looks a lot
    > more useful:
    >
    > aldebaran:~/linux/linux> make -j32 >e
    > sound/pci/hda/patch_sigmatel.c: In function ‘stac92xx_init’:
    > sound/pci/hda/patch_sigmatel.c:4385:3: warning: statement with no
    > effect [-Wunused-value]
    > sound/pci/hda/patch_sigmatel.c: In function ‘stac92xx_resume’:
    > sound/pci/hda/patch_sigmatel.c:4925:3: warning: statement with no
    > effect [-Wunused-value]
    > sound/pci/hda/patch_realtek.c: In function ‘alc_init’:
    > sound/pci/hda/patch_realtek.c:4176:2: warning: statement with no
    > effect [-Wunused-value]
    > sound/pci/hda/patch_realtek.c: In function ‘alc_resume’:
    > sound/pci/hda/patch_realtek.c:4558:2: warning: statement with no
    > effect [-Wunused-value]
    > sound/pci/hda/hda_codec.c: In function
    > ‘snd_hda_mixer_amp_switch_put’:
    > sound/pci/hda/hda_codec.c:2320:2: warning: statement with no effect
    > [-Wunused-value]
    > sound/pci/hda/patch_realtek.c: In function ‘alc269_resume’:
    > sound/pci/hda/patch_realtek.c:14878:2: warning: statement with no
    > effect [-Wunused-value]
    > drivers/md/dm.c: In function ‘split_bvec’:
    > drivers/md/dm.c:1052:3: warning: statement with no effect
    > [-Wunused-value]
    > drivers/md/dm.c: In function ‘clone_bio’:
    > drivers/md/dm.c:1079:3: warning: statement with no effect
    > [-Wunused-value]
    > drivers/md/dm-table.c: In function ‘dm_table_set_integrity’:
    > drivers/md/dm-table.c:1193:2: warning: statement with no effect
    > [-Wunused-value]
    > Setup is 15260 bytes (padded to 15360 bytes).
    > System is 4654 kB
    > CRC 6d1b94ea
    >
    > those unused-x warnings seem legit and should be fixed. For example
    > the second patch below fixed the dm.c warnings.
    >
    > That's with:
    >
    >  gcc version 4.6.0 20110509 (Red Hat 4.6.0-7) (GCC)
    >
    > so a reasonably recent GCC. I think we should kill -Waddress.
    >
    > Thanks,
    >
    >        Ingo
    >
    > diff --git a/Makefile b/Makefile
    > index d018956..e651294 100644
    > --- a/Makefile
    > +++ b/Makefile
    > @@ -559,9 +559,9 @@ endif # $(dot-config)
    >  all: vmlinux
    >
    >  ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
    > -KBUILD_CFLAGS  += -Os
    > +KBUILD_CFLAGS  += -Os -Wno-address
    >  else
    > -KBUILD_CFLAGS  += -O2
    > +KBUILD_CFLAGS  += -O2 -Wno-address
    >  endif
    >
    did you submit this to linux-kbuild@ ?

    >  include $(srctree)/arch/$(SRCARCH)/Makefile
    >
    > diff --git a/include/linux/bio.h b/include/linux/bio.h
    > index ce33e68..283250a 100644
    > --- a/include/linux/bio.h
    > +++ b/include/linux/bio.h
    > @@ -527,7 +527,7 @@ extern void bio_integrity_init(void);
    >  #define bioset_integrity_create(a, b)  (0)
    >  #define bio_integrity_prep(a)          (0)
    >  #define bio_integrity_enabled(a)       (0)
    > -#define bio_integrity_clone(a, b, c, d)        (0)
    > +#define bio_integrity_clone(a, b, c, d)        ({0;})
    >  #define bioset_integrity_free(a)       do { } while (0)
    >  #define bio_integrity_free(a, b)       do { } while (0)
    >  #define bio_integrity_endio(a, b)      do { } while (0)
    >
    likewise, but to the maintainer of `include/linux/bio.h' ?
    --
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