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SubjectRe: [PATCH v2] arch/powerpc: Rework local_paca to avoid LTO warnings
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Le 14/03/2019 à 03:31, Alastair D'Silva a écrit :
> From: Alastair D'Silva <alastair@d-silva.org>
>
> When building an LTO kernel, the existing code generates warnings:
> ./arch/powerpc/include/asm/paca.h:37:30: warning: register of
> ‘local_paca’ used for multiple global register variables
> register struct paca_struct *local_paca asm("r13");
> ^
> ./arch/powerpc/include/asm/paca.h:37:30: note: conflicts with
> ‘local_paca’
>
> This patch reworks local_paca into an inline getter & setter function,
> which addresses the warning.
>
> Changelog:
> V2
> - Address whitespace issues
> - keep new implementation close to where the old implementation was
>
> Signed-off-by: Alastair D'Silva <alastair@d-silva.org>

Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>

> ---
> arch/powerpc/include/asm/paca.h | 37 +++++++++++++++++++++++++--------
> arch/powerpc/kernel/paca.c | 2 +-
> 2 files changed, 29 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
> index e843bc5d1a0f..2fa0b43357c9 100644
> --- a/arch/powerpc/include/asm/paca.h
> +++ b/arch/powerpc/include/asm/paca.h
> @@ -34,19 +34,38 @@
> #include <asm/cpuidle.h>
> #include <asm/atomic.h>
>
> -register struct paca_struct *local_paca asm("r13");
> -
> #if defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_SMP)
> extern unsigned int debug_smp_processor_id(void); /* from linux/smp.h */
> -/*
> - * Add standard checks that preemption cannot occur when using get_paca():
> - * otherwise the paca_struct it points to may be the wrong one just after.
> - */
> -#define get_paca() ((void) debug_smp_processor_id(), local_paca)
> -#else
> -#define get_paca() local_paca
> #endif
>
> +static inline struct paca_struct *get_paca_no_preempt_check(void)
> +{
> + register struct paca_struct *paca asm("r13");
> +
> + return paca;
> +}
> +
> +static inline struct paca_struct *get_paca(void)
> +{
> +#if defined(CONFIG_DEBUG_PREEMPT) && defined(CONFIG_SMP)
> + /*
> + * Add standard checks that preemption cannot occur when using get_paca():
> + * otherwise the paca_struct it points to may be the wrong one just after.
> + */
> + debug_smp_processor_id();
> +#endif
> + return get_paca_no_preempt_check();
> +}
> +
> +#define local_paca get_paca_no_preempt_check()
> +
> +static inline void set_paca(struct paca_struct *new)
> +{
> + register struct paca_struct *paca asm("r13");
> +
> + paca = new;
> +}
> +
> #ifdef CONFIG_PPC_PSERIES
> #define get_lppaca() (get_paca()->lppaca_ptr)
> #endif
> diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
> index 913bfca09c4f..ae5c243f9d5a 100644
> --- a/arch/powerpc/kernel/paca.c
> +++ b/arch/powerpc/kernel/paca.c
> @@ -172,7 +172,7 @@ void __init initialise_paca(struct paca_struct *new_paca, int cpu)
> void setup_paca(struct paca_struct *new_paca)
> {
> /* Setup r13 */
> - local_paca = new_paca;
> + set_paca(new_paca);
>
> #ifdef CONFIG_PPC_BOOK3E
> /* On Book3E, initialize the TLB miss exception frames */
>

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