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Diffstat (limited to 'include/linux/context_tracking_state.h')
| -rw-r--r-- | include/linux/context_tracking_state.h | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h new file mode 100644 index 000000000000..0b81248aa03e --- /dev/null +++ b/include/linux/context_tracking_state.h @@ -0,0 +1,178 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _LINUX_CONTEXT_TRACKING_STATE_H +#define _LINUX_CONTEXT_TRACKING_STATE_H + +#include <linux/percpu.h> +#include <linux/static_key.h> +#include <linux/context_tracking_irq.h> + +/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */ +#define CT_NESTING_IRQ_NONIDLE ((LONG_MAX / 2) + 1) + +enum ctx_state { + CT_STATE_DISABLED = -1, /* returned by ct_state() if unknown */ + CT_STATE_KERNEL = 0, + CT_STATE_IDLE = 1, + CT_STATE_USER = 2, + CT_STATE_GUEST = 3, + CT_STATE_MAX = 4, +}; + +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); +} + +static __always_inline long ct_nesting_cpu(int cpu) +{ + struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu); + + return ct->nesting; +} + +static __always_inline long ct_nmi_nesting(void) +{ + return __this_cpu_read(context_tracking.nmi_nesting); +} + +static __always_inline long ct_nmi_nesting_cpu(int cpu) +{ + struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu); + + return ct->nmi_nesting; +} +#endif /* #ifdef CONFIG_CONTEXT_TRACKING_IDLE */ + +#ifdef CONFIG_CONTEXT_TRACKING_USER +extern struct static_key_false context_tracking_key; + +static __always_inline bool context_tracking_enabled(void) +{ + return static_branch_unlikely(&context_tracking_key); +} + +static __always_inline bool context_tracking_enabled_cpu(int cpu) +{ + return context_tracking_enabled() && per_cpu(context_tracking.active, cpu); +} + +static __always_inline bool context_tracking_enabled_this_cpu(void) +{ + return context_tracking_enabled() && __this_cpu_read(context_tracking.active); +} + +/** + * ct_state() - return the current context tracking state if known + * + * Returns the current cpu's context tracking state if context tracking + * is enabled. If context tracking is disabled, returns + * CT_STATE_DISABLED. This should be used primarily for debugging. + */ +static __always_inline int ct_state(void) +{ + int ret; + + if (!context_tracking_enabled()) + return CT_STATE_DISABLED; + + preempt_disable(); + ret = __ct_state(); + preempt_enable(); + + return ret; +} + +#else +static __always_inline bool context_tracking_enabled(void) { return false; } +static __always_inline bool context_tracking_enabled_cpu(int cpu) { return false; } +static __always_inline bool context_tracking_enabled_this_cpu(void) { return false; } +#endif /* CONFIG_CONTEXT_TRACKING_USER */ + +#endif |