On Thursday, August 11, 2016 4:01:33 PM CEST Nicolas Pitre wrote:
> > #ifdef CONFIG_SMP_ON_UP
> > .init.smpalt : {
> > __smpalt_begin = .;
> > - *(.alt.smp.init)
> > + KEEP(*(.alt.smp.init))
>
> Yes unfortunately this needs a KEEP() right now as there is no explicit
> references to those entries. But by doing so you force a reference from
> those entries to all functions they annotate, preventing those functions
> from being discarded if there isn't any reference to that code
> otherwise. That's a case that falls into the "missing forward reference"
> category in my slides.
I see. This actually relates to an existing problem with SMP alternatives
in exit sections, which cause a linker error. I've done a patch for
this at some point, but didn't feel confident enough to send it out
commit 0c598e53b3a0ad7daf077603618001edcf9bface
Author: Arnd Bergmann <arnd@xxxxxxxx>
Date: Sun Mar 16 20:14:30 2014 +0100
ARM: don't discard exit sections for spinlock debugging
This avoids lots of warnings like this one:
`.exit.text' referenced in section `.alt.smp.init' of drivers/built-in.o: defined in discarded section `.exit.text' of drivers/built-in.o
for each spinlock that is used in an __exit function, because
the smp alternatives try to patch out the spinlock locations.
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
index d24e5dd2aa7a..1f5eeeb4c8d0 100644
--- a/arch/arm/kernel/vmlinux.lds.S
+++ b/arch/arm/kernel/vmlinux.lds.S
@@ -43,8 +43,7 @@
#define ARM_CPU_KEEP(x)
#endif
-#if (defined(CONFIG_SMP_ON_UP) && !defined(CONFIG_DEBUG_SPINLOCK)) || \
- defined(CONFIG_GENERIC_BUG) || defined(CONFIG_JUMP_LABEL)
+#if defined(CONFIG_SMP_ON_UP) || defined(CONFIG_GENERIC_BUG) || defined(CONFIG_JUMP_LABEL)
#define ARM_EXIT_KEEP(x) x
#define ARM_EXIT_DISCARD(x)
#else
--
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