arch/arc/include/asm/smp.h

Source file repositories/reference/linux-study-clean/arch/arc/include/asm/smp.h

File Facts

System
Linux kernel
Corpus path
arch/arc/include/asm/smp.h
Extension
.h
Size
3913 bytes
Lines
131
Domain
Architecture Layer
Bucket
arch/arc
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

struct plat_smp_ops {
	const char 	*info;
	void		(*init_early_smp)(void);
	void		(*init_per_cpu)(int cpu);
	void		(*cpu_kick)(int cpu, unsigned long pc);
	void		(*ipi_send)(int cpu);
	void		(*ipi_clear)(int irq);
};

/* TBD: stop exporting it for direct population by platform */
extern struct plat_smp_ops  plat_smp_ops;

#else /* CONFIG_SMP */

static inline void smp_init_cpus(void) {}
static inline const char *arc_platform_smp_cpuinfo(void)
{
	return "";
}

#endif  /* !CONFIG_SMP */

/*
 * ARC700 doesn't support atomic Read-Modify-Write ops.
 * Originally Interrupts had to be disabled around code to guarantee atomicity.
 * The LLOCK/SCOND insns allow writing interrupt-hassle-free based atomic ops
 * based on retry-if-irq-in-atomic (with hardware assist).
 * However despite these, we provide the IRQ disabling variant
 *
 * (1) These insn were introduced only in 4.10 release. So for older released
 *	support needed.
 *
 * (2) In a SMP setup, the LLOCK/SCOND atomicity across CPUs needs to be
 *	guaranteed by the platform (not something which core handles).
 *	Assuming a platform won't, SMP Linux needs to use spinlocks + local IRQ
 *	disabling for atomicity.
 *
 *	However exported spinlock API is not usable due to cyclic hdr deps
 *	(even after system.h disintegration upstream)
 *	asm/bitops.h -> linux/spinlock.h -> linux/preempt.h
 *		-> linux/thread_info.h -> linux/bitops.h -> asm/bitops.h
 *
 *	So the workaround is to use the lowest level arch spinlock API.
 *	The exported spinlock API is smart enough to be NOP for !CONFIG_SMP,
 *	but same is not true for ARCH backend, hence the need for 2 variants
 */
#ifndef CONFIG_ARC_HAS_LLSC

#include <linux/irqflags.h>
#ifdef CONFIG_SMP

#include <asm/spinlock.h>

extern arch_spinlock_t smp_atomic_ops_lock;

#define atomic_ops_lock(flags)	do {		\
	local_irq_save(flags);			\
	arch_spin_lock(&smp_atomic_ops_lock);	\
} while (0)

#define atomic_ops_unlock(flags) do {		\
	arch_spin_unlock(&smp_atomic_ops_lock);	\
	local_irq_restore(flags);		\
} while (0)

#else /* !CONFIG_SMP */

#define atomic_ops_lock(flags)		local_irq_save(flags)
#define atomic_ops_unlock(flags)	local_irq_restore(flags)

#endif /* !CONFIG_SMP */

#endif	/* !CONFIG_ARC_HAS_LLSC */

#endif

Annotation

Implementation Notes