* [PATCH] ia64: Depend on non-static printk for cmpxchg debug
@ 2021-02-13 14:41 Chris Down
2021-02-26 12:47 ` Chris Down
0 siblings, 1 reply; 6+ messages in thread
From: Chris Down @ 2021-02-13 14:41 UTC (permalink / raw)
To: linux-ia64; +Cc: Tony Luck, Fenghua Yu, linux-kernel, kernel-team
With !CONFIG_PRINTK, printk() is static in the header, but ia64's
cmpxchg.h with CONFIG_IA64_DEBUG_CMPXCHG doesn't take this into account
before trying to use it as extern, resulting in a compiler error:
./include/linux/printk.h:219:5: error: static declaration of 'printk' follows non-static declaration
219 | int printk(const char *s, ...)
| ^~~~~~
./arch/ia64/include/uapi/asm/cmpxchg.h:142:14: note: previous declaration of 'printk' was here
142 | extern int printk(const char *fmt, ...); \
| ^~~~~~
Make CONFIG_IA64_DEBUG_CMPXCHG dependent on CONFIG_PRINTK to avoid this.
Signed-off-by: Chris Down <chris@chrisdown.name>
Reported-by: kernel test robot <lkp@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: linux-ia64@vger.kernel.org
---
arch/ia64/Kconfig.debug | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/ia64/Kconfig.debug b/arch/ia64/Kconfig.debug
index 40ca23bd228d..2ce008e2d164 100644
--- a/arch/ia64/Kconfig.debug
+++ b/arch/ia64/Kconfig.debug
@@ -39,7 +39,7 @@ config DISABLE_VHPT
config IA64_DEBUG_CMPXCHG
bool "Turn on compare-and-exchange bug checking (slow!)"
- depends on DEBUG_KERNEL
+ depends on DEBUG_KERNEL && PRINTK
help
Selecting this option turns on bug checking for the IA-64
compare-and-exchange instructions. This is slow! Itaniums
--
2.30.1
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] ia64: Depend on non-static printk for cmpxchg debug
2021-02-13 14:41 [PATCH] ia64: Depend on non-static printk for cmpxchg debug Chris Down
@ 2021-02-26 12:47 ` Chris Down
2021-02-26 13:00 ` Matthew Wilcox
0 siblings, 1 reply; 6+ messages in thread
From: Chris Down @ 2021-02-26 12:47 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, Tony Luck, Fenghua Yu, linux-ia64, linux-kernel,
kernel-team
+ akpm, linux-mm
Hey folks,
Chris Down writes:
>With !CONFIG_PRINTK, printk() is static in the header, but ia64's
>cmpxchg.h with CONFIG_IA64_DEBUG_CMPXCHG doesn't take this into account
>before trying to use it as extern, resulting in a compiler error:
>
> ./include/linux/printk.h:219:5: error: static declaration of 'printk' follows non-static declaration
> 219 | int printk(const char *s, ...)
> | ^~~~~~
> ./arch/ia64/include/uapi/asm/cmpxchg.h:142:14: note: previous declaration of 'printk' was here
> 142 | extern int printk(const char *fmt, ...); \
> | ^~~~~~
>
>Make CONFIG_IA64_DEBUG_CMPXCHG dependent on CONFIG_PRINTK to avoid this.
>
>Signed-off-by: Chris Down <chris@chrisdown.name>
>Reported-by: kernel test robot <lkp@intel.com>
>Cc: Tony Luck <tony.luck@intel.com>
>Cc: Fenghua Yu <fenghua.yu@intel.com>
>Cc: linux-ia64@vger.kernel.org
I now see that last month ia64 was marked as orphaned, so I'm going to send
this over to Andrew/-mm.
Andrew, any chance you can take this in your tree? It's causing spurious LKP
noise for some recent work on printk and would be great to have in -next.
Thanks,
Chris
>---
> arch/ia64/Kconfig.debug | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/arch/ia64/Kconfig.debug b/arch/ia64/Kconfig.debug
>index 40ca23bd228d..2ce008e2d164 100644
>--- a/arch/ia64/Kconfig.debug
>+++ b/arch/ia64/Kconfig.debug
>@@ -39,7 +39,7 @@ config DISABLE_VHPT
>
> config IA64_DEBUG_CMPXCHG
> bool "Turn on compare-and-exchange bug checking (slow!)"
>- depends on DEBUG_KERNEL
>+ depends on DEBUG_KERNEL && PRINTK
> help
> Selecting this option turns on bug checking for the IA-64
> compare-and-exchange instructions. This is slow! Itaniums
>--
>2.30.1
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] ia64: Depend on non-static printk for cmpxchg debug
2021-02-26 12:47 ` Chris Down
@ 2021-02-26 13:00 ` Matthew Wilcox
2021-02-26 13:14 ` Chris Down
0 siblings, 1 reply; 6+ messages in thread
From: Matthew Wilcox @ 2021-02-26 13:00 UTC (permalink / raw)
To: Chris Down
Cc: Andrew Morton, linux-mm, Tony Luck, Fenghua Yu, linux-ia64,
linux-kernel, kernel-team
On Fri, Feb 26, 2021 at 12:47:58PM +0000, Chris Down wrote:
> > ./include/linux/printk.h:219:5: error: static declaration of 'printk' follows non-static declaration
> > 219 | int printk(const char *s, ...)
> > | ^~~~~~
> > ./arch/ia64/include/uapi/asm/cmpxchg.h:142:14: note: previous declaration of 'printk' was here
> > 142 | extern int printk(const char *fmt, ...); \
> > | ^~~~~~
> >
> > Make CONFIG_IA64_DEBUG_CMPXCHG dependent on CONFIG_PRINTK to avoid this.
Why not just fix it?
diff --git a/arch/ia64/include/uapi/asm/cmpxchg.h b/arch/ia64/include/uapi/asm/cmpxchg.h
index 5d90307fd6e0..d955a8e3ebde 100644
--- a/arch/ia64/include/uapi/asm/cmpxchg.h
+++ b/arch/ia64/include/uapi/asm/cmpxchg.h
@@ -139,7 +139,7 @@ extern long ia64_cmpxchg_called_with_bad_pointer(void);
do { \
if (_cmpxchg_bugcheck_count-- <= 0) { \
void *ip; \
- extern int printk(const char *fmt, ...); \
+ int printk(const char *fmt, ...); \
ip = (void *) ia64_getreg(_IA64_REG_IP); \
printk("CMPXCHG_BUGCHECK: stuck at %p on word %p\n", ip, (v));\
break; \
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] ia64: Depend on non-static printk for cmpxchg debug
2021-02-26 13:00 ` Matthew Wilcox
@ 2021-02-26 13:14 ` Chris Down
2021-02-26 13:47 ` Chris Down
0 siblings, 1 reply; 6+ messages in thread
From: Chris Down @ 2021-02-26 13:14 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Andrew Morton, linux-mm, Tony Luck, Fenghua Yu, linux-ia64,
linux-kernel, kernel-team
Matthew Wilcox writes:
>Why not just fix it?
>
>diff --git a/arch/ia64/include/uapi/asm/cmpxchg.h b/arch/ia64/include/uapi/asm/cmpxchg.h
>index 5d90307fd6e0..d955a8e3ebde 100644
>--- a/arch/ia64/include/uapi/asm/cmpxchg.h
>+++ b/arch/ia64/include/uapi/asm/cmpxchg.h
>@@ -139,7 +139,7 @@ extern long ia64_cmpxchg_called_with_bad_pointer(void);
> do { \
> if (_cmpxchg_bugcheck_count-- <= 0) { \
> void *ip; \
>- extern int printk(const char *fmt, ...); \
>+ int printk(const char *fmt, ...); \
> ip = (void *) ia64_getreg(_IA64_REG_IP); \
> printk("CMPXCHG_BUGCHECK: stuck at %p on word %p\n", ip, (v));\
> break; \
I must confess I have no idea of the history of why it was `extern int` in the
first place -- my fear was somehow we use cmpxchg.h from a different context.
Do you have any idea? :-)
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] ia64: Depend on non-static printk for cmpxchg debug
2021-02-26 13:14 ` Chris Down
@ 2021-02-26 13:47 ` Chris Down
2021-02-26 13:50 ` Matthew Wilcox
0 siblings, 1 reply; 6+ messages in thread
From: Chris Down @ 2021-02-26 13:47 UTC (permalink / raw)
To: Matthew Wilcox
Cc: Andrew Morton, linux-mm, Tony Luck, Fenghua Yu, linux-ia64,
linux-kernel, kernel-team
Chris Down writes:
>I must confess I have no idea of the history of why it was `extern
>int` in the first place -- my fear was somehow we use cmpxchg.h from a
>different context. Do you have any idea? :-)
Ok, found where it's introduced in the pre-git archives: "New file
asm-ia64/intrinsics.h." from David Mosberger <davidm@tiger.hpl.hp.com>, Dec 9
2002. No indication why it's extern, but it's been there since the dawn of
ia64.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] ia64: Depend on non-static printk for cmpxchg debug
2021-02-26 13:47 ` Chris Down
@ 2021-02-26 13:50 ` Matthew Wilcox
0 siblings, 0 replies; 6+ messages in thread
From: Matthew Wilcox @ 2021-02-26 13:50 UTC (permalink / raw)
To: Chris Down
Cc: Andrew Morton, linux-mm, Tony Luck, Fenghua Yu, linux-ia64,
linux-kernel, kernel-team
On Fri, Feb 26, 2021 at 01:47:20PM +0000, Chris Down wrote:
> Chris Down writes:
> > I must confess I have no idea of the history of why it was `extern int`
> > in the first place -- my fear was somehow we use cmpxchg.h from a
> > different context. Do you have any idea? :-)
>
> Ok, found where it's introduced in the pre-git archives: "New file
> asm-ia64/intrinsics.h." from David Mosberger <davidm@tiger.hpl.hp.com>, Dec
> 9 2002. No indication why it's extern, but it's been there since the dawn of
> ia64.
It's just a quirk of C. 'extern' is only meaningful when applied to
variables. In the context of functions,
extern int printk(char *fmt);
int printk(char *fmt);
are completely equivalent. Unless (as you've seen) there's then a
static definition following the extern declaration.
^ permalink raw reply [flat|nested] 6+ messages in thread
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2021-02-13 14:41 [PATCH] ia64: Depend on non-static printk for cmpxchg debug Chris Down
2021-02-26 12:47 ` Chris Down
2021-02-26 13:00 ` Matthew Wilcox
2021-02-26 13:14 ` Chris Down
2021-02-26 13:47 ` Chris Down
2021-02-26 13:50 ` Matthew Wilcox
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