include/linux/context_tracking_state.h

Source file repositories/reference/linux-study-clean/include/linux/context_tracking_state.h

File Facts

System
Linux kernel
Corpus path
include/linux/context_tracking_state.h
Extension
.h
Size
5227 bytes
Lines
179
Domain
Core OS
Bucket
Core Kernel Interface
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

struct context_tracking {
#ifdef CONFIG_CONTEXT_TRACKING_USER
	/*
	 * When active is false, probes are unset in order
	 * to minimize overhead: TIF flags are cleared
	 * and calls to user_enter/exit are ignored. This
	 * may be further optimized using static keys.
	 */
	bool active;
	int recursion;
#endif
#ifdef CONFIG_CONTEXT_TRACKING
	atomic_t state;
#endif
#ifdef CONFIG_CONTEXT_TRACKING_IDLE
	long nesting;		/* Track process nesting level. */
	long nmi_nesting;	/* Track irq/NMI nesting level. */
#endif
};

/*
 * We cram two different things within the same atomic variable:
 *
 *                     CT_RCU_WATCHING_START  CT_STATE_START
 *                                |                |
 *                                v                v
 *     MSB [ RCU watching counter ][ context_state ] LSB
 *         ^                       ^
 *         |                       |
 * CT_RCU_WATCHING_END        CT_STATE_END
 *
 * Bits are used from the LSB upwards, so unused bits (if any) will always be in
 * upper bits of the variable.
 */
#ifdef CONFIG_CONTEXT_TRACKING
#define CT_SIZE (sizeof(((struct context_tracking *)0)->state) * BITS_PER_BYTE)

#define CT_STATE_WIDTH bits_per(CT_STATE_MAX - 1)
#define CT_STATE_START 0
#define CT_STATE_END   (CT_STATE_START + CT_STATE_WIDTH - 1)

#define CT_RCU_WATCHING_MAX_WIDTH (CT_SIZE - CT_STATE_WIDTH)
#define CT_RCU_WATCHING_WIDTH     (IS_ENABLED(CONFIG_RCU_DYNTICKS_TORTURE) ? 2 : CT_RCU_WATCHING_MAX_WIDTH)
#define CT_RCU_WATCHING_START     (CT_STATE_END + 1)
#define CT_RCU_WATCHING_END       (CT_RCU_WATCHING_START + CT_RCU_WATCHING_WIDTH - 1)
#define CT_RCU_WATCHING           BIT(CT_RCU_WATCHING_START)

#define CT_STATE_MASK        GENMASK(CT_STATE_END,        CT_STATE_START)
#define CT_RCU_WATCHING_MASK GENMASK(CT_RCU_WATCHING_END, CT_RCU_WATCHING_START)

#define CT_UNUSED_WIDTH (CT_RCU_WATCHING_MAX_WIDTH - CT_RCU_WATCHING_WIDTH)

static_assert(CT_STATE_WIDTH        +
	      CT_RCU_WATCHING_WIDTH +
	      CT_UNUSED_WIDTH       ==
	      CT_SIZE);

DECLARE_PER_CPU(struct context_tracking, context_tracking);
#endif	/* CONFIG_CONTEXT_TRACKING */

#ifdef CONFIG_CONTEXT_TRACKING_USER
static __always_inline int __ct_state(void)
{
	return raw_atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_STATE_MASK;
}
#endif

#ifdef CONFIG_CONTEXT_TRACKING_IDLE
static __always_inline int ct_rcu_watching(void)
{
	return atomic_read(this_cpu_ptr(&context_tracking.state)) & CT_RCU_WATCHING_MASK;
}

static __always_inline int ct_rcu_watching_cpu(int cpu)
{
	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);

	return atomic_read(&ct->state) & CT_RCU_WATCHING_MASK;
}

static __always_inline int ct_rcu_watching_cpu_acquire(int cpu)
{
	struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);

	return atomic_read_acquire(&ct->state) & CT_RCU_WATCHING_MASK;
}

static __always_inline long ct_nesting(void)
{
	return __this_cpu_read(context_tracking.nesting);

Annotation

Implementation Notes