diff options
Diffstat (limited to 'include/linux/srcutree.h')
| -rw-r--r-- | include/linux/srcutree.h | 259 |
1 files changed, 230 insertions, 29 deletions
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 9cfcc8a756ae..8bed7e6cc4c1 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -17,14 +17,21 @@ struct srcu_node; struct srcu_struct; +/* One element of the srcu_data srcu_ctrs array. */ +struct srcu_ctr { + atomic_long_t srcu_locks; /* Locks per CPU. */ + atomic_long_t srcu_unlocks; /* Unlocks per CPU. */ +}; + /* * Per-CPU structure feeding into leaf srcu_node, similar in function * to rcu_node. */ struct srcu_data { /* Read-side state. */ - unsigned long srcu_lock_count[2]; /* Locks per CPU. */ - unsigned long srcu_unlock_count[2]; /* Unlocks per CPU. */ + struct srcu_ctr srcu_ctrs[2]; /* Locks and unlocks per CPU. */ + int srcu_reader_flavor; /* Reader flavor for srcu_struct structure? */ + /* Values: SRCU_READ_FLAVOR_.* */ /* Update-side state. */ spinlock_t __private lock ____cacheline_internodealigned_in_smp; @@ -47,11 +54,9 @@ struct srcu_data { */ struct srcu_node { spinlock_t __private lock; - unsigned long srcu_have_cbs[4]; /* GP seq for children */ - /* having CBs, but only */ - /* is > ->srcu_gq_seq. */ - unsigned long srcu_data_have_cbs[4]; /* Which srcu_data structs */ - /* have CBs for given GP? */ + unsigned long srcu_have_cbs[4]; /* GP seq for children having CBs, but only */ + /* if greater than ->srcu_gp_seq. */ + unsigned long srcu_data_have_cbs[4]; /* Which srcu_data structs have CBs for given GP? */ unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */ struct srcu_node *srcu_parent; /* Next up in tree. */ int grplo; /* Least CPU for node. */ @@ -59,21 +64,25 @@ struct srcu_node { }; /* - * Per-SRCU-domain structure, similar in function to rcu_state. + * Per-SRCU-domain structure, update-side data linked from srcu_struct. */ -struct srcu_struct { - struct srcu_node node[NUM_RCU_NODES]; /* Combining tree. */ +struct srcu_usage { + struct srcu_node *node; /* Combining tree. */ struct srcu_node *level[RCU_NUM_LVLS + 1]; /* First node at each level. */ + int srcu_size_state; /* Small-to-big transition state. */ struct mutex srcu_cb_mutex; /* Serialize CB preparation. */ - spinlock_t __private lock; /* Protect counters */ + spinlock_t __private lock; /* Protect counters and size state. */ struct mutex srcu_gp_mutex; /* Serialize GP work. */ - unsigned int srcu_idx; /* Current rdr array element. */ unsigned long srcu_gp_seq; /* Grace-period seq #. */ unsigned long srcu_gp_seq_needed; /* Latest gp_seq needed. */ unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */ + unsigned long srcu_gp_start; /* Last GP start timestamp (jiffies) */ unsigned long srcu_last_gp_end; /* Last GP end timestamp (ns) */ - struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */ + unsigned long srcu_size_jiffies; /* Current contention-measurement interval. */ + unsigned long srcu_n_lock_retries; /* Contention events in current interval. */ + unsigned long srcu_n_exp_nodelay; /* # expedited no-delays in current GP phase. */ + bool sda_is_static; /* May ->sda be passed to free_percpu()? */ unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */ struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */ struct completion srcu_barrier_completion; @@ -81,24 +90,85 @@ struct srcu_struct { atomic_t srcu_barrier_cpu_cnt; /* # CPUs not yet posting a */ /* callback for the barrier */ /* operation. */ + unsigned long reschedule_jiffies; + unsigned long reschedule_count; struct delayed_work work; -#ifdef CONFIG_DEBUG_LOCK_ALLOC + struct srcu_struct *srcu_ssp; +}; + +/* + * Per-SRCU-domain structure, similar in function to rcu_state. + */ +struct srcu_struct { + struct srcu_ctr __percpu *srcu_ctrp; + struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */ struct lockdep_map dep_map; -#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + struct srcu_usage *srcu_sup; /* Update-side data. */ }; +// Values for size state variable (->srcu_size_state). Once the state +// has been set to SRCU_SIZE_ALLOC, the grace-period code advances through +// this state machine one step per grace period until the SRCU_SIZE_BIG state +// is reached. Otherwise, the state machine remains in the SRCU_SIZE_SMALL +// state indefinitely. +#define SRCU_SIZE_SMALL 0 // No srcu_node combining tree, ->node == NULL +#define SRCU_SIZE_ALLOC 1 // An srcu_node tree is being allocated, initialized, + // and then referenced by ->node. It will not be used. +#define SRCU_SIZE_WAIT_BARRIER 2 // The srcu_node tree starts being used by everything + // except call_srcu(), especially by srcu_barrier(). + // By the end of this state, all CPUs and threads + // are aware of this tree's existence. +#define SRCU_SIZE_WAIT_CALL 3 // The srcu_node tree starts being used by call_srcu(). + // By the end of this state, all of the call_srcu() + // invocations that were running on a non-boot CPU + // and using the boot CPU's callback queue will have + // completed. +#define SRCU_SIZE_WAIT_CBS1 4 // Don't trust the ->srcu_have_cbs[] grace-period +#define SRCU_SIZE_WAIT_CBS2 5 // sequence elements or the ->srcu_data_have_cbs[] +#define SRCU_SIZE_WAIT_CBS3 6 // CPU-bitmask elements until all four elements of +#define SRCU_SIZE_WAIT_CBS4 7 // each array have been initialized. +#define SRCU_SIZE_BIG 8 // The srcu_node combining tree is fully initialized + // and all aspects of it are being put to use. + /* Values for state variable (bottom bits of ->srcu_gp_seq). */ #define SRCU_STATE_IDLE 0 #define SRCU_STATE_SCAN1 1 #define SRCU_STATE_SCAN2 2 -#define __SRCU_STRUCT_INIT(name, pcpu_name) \ -{ \ - .sda = &pcpu_name, \ - .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ - .srcu_gp_seq_needed = -1UL, \ - .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \ - __SRCU_DEP_MAP_INIT(name) \ +/* + * Values for initializing gp sequence fields. Higher values allow wrap arounds to + * occur earlier. + * The second value with state is useful in the case of static initialization of + * srcu_usage where srcu_gp_seq_needed is expected to have some state value in its + * lower bits (or else it will appear to be already initialized within + * the call check_init_srcu_struct()). + */ +#define SRCU_GP_SEQ_INITIAL_VAL ((0UL - 100UL) << RCU_SEQ_CTR_SHIFT) +#define SRCU_GP_SEQ_INITIAL_VAL_WITH_STATE (SRCU_GP_SEQ_INITIAL_VAL - 1) + +#define __SRCU_USAGE_INIT(name) \ +{ \ + .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ + .srcu_gp_seq = SRCU_GP_SEQ_INITIAL_VAL, \ + .srcu_gp_seq_needed = SRCU_GP_SEQ_INITIAL_VAL_WITH_STATE, \ + .srcu_gp_seq_needed_exp = SRCU_GP_SEQ_INITIAL_VAL, \ + .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \ +} + +#define __SRCU_STRUCT_INIT_COMMON(name, usage_name) \ + .srcu_sup = &usage_name, \ + __SRCU_DEP_MAP_INIT(name) + +#define __SRCU_STRUCT_INIT_MODULE(name, usage_name) \ +{ \ + __SRCU_STRUCT_INIT_COMMON(name, usage_name) \ +} + +#define __SRCU_STRUCT_INIT(name, usage_name, pcpu_name) \ +{ \ + .sda = &pcpu_name, \ + .srcu_ctrp = &pcpu_name.srcu_ctrs[0], \ + __SRCU_STRUCT_INIT_COMMON(name, usage_name) \ } /* @@ -121,21 +191,152 @@ struct srcu_struct { * See include/linux/percpu-defs.h for the rules on per-CPU variables. */ #ifdef MODULE -# define __DEFINE_SRCU(name, is_static) \ - is_static struct srcu_struct name; \ - struct srcu_struct * const __srcu_struct_##name \ +# define __DEFINE_SRCU(name, is_static) \ + static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage); \ + is_static struct srcu_struct name = __SRCU_STRUCT_INIT_MODULE(name, name##_srcu_usage); \ + extern struct srcu_struct * const __srcu_struct_##name; \ + struct srcu_struct * const __srcu_struct_##name \ __section("___srcu_struct_ptrs") = &name #else -# define __DEFINE_SRCU(name, is_static) \ - static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data); \ - is_static struct srcu_struct name = \ - __SRCU_STRUCT_INIT(name, name##_srcu_data) +# define __DEFINE_SRCU(name, is_static) \ + static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data); \ + static struct srcu_usage name##_srcu_usage = __SRCU_USAGE_INIT(name##_srcu_usage); \ + is_static struct srcu_struct name = \ + __SRCU_STRUCT_INIT(name, name##_srcu_usage, name##_srcu_data) #endif #define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */) #define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static) +int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); void synchronize_srcu_expedited(struct srcu_struct *ssp); void srcu_barrier(struct srcu_struct *ssp); void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf); +// Converts a per-CPU pointer to an ->srcu_ctrs[] array element to that +// element's index. +static inline bool __srcu_ptr_to_ctr(struct srcu_struct *ssp, struct srcu_ctr __percpu *scpp) +{ + return scpp - &ssp->sda->srcu_ctrs[0]; +} + +// Converts an integer to a per-CPU pointer to the corresponding +// ->srcu_ctrs[] array element. +static inline struct srcu_ctr __percpu *__srcu_ctr_to_ptr(struct srcu_struct *ssp, int idx) +{ + return &ssp->sda->srcu_ctrs[idx]; +} + +/* + * Counts the new reader in the appropriate per-CPU element of the + * srcu_struct. Returns a pointer that must be passed to the matching + * srcu_read_unlock_fast(). + * + * Note that both this_cpu_inc() and atomic_long_inc() are RCU read-side + * critical sections either because they disables interrupts, because they + * are a single instruction, or because they are a read-modify-write atomic + * operation, depending on the whims of the architecture. + * + * This means that __srcu_read_lock_fast() is not all that fast + * on architectures that support NMIs but do not supply NMI-safe + * implementations of this_cpu_inc(). + */ +static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct *ssp) +{ + struct srcu_ctr __percpu *scp = READ_ONCE(ssp->srcu_ctrp); + + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_fast()."); + if (!IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE)) + this_cpu_inc(scp->srcu_locks.counter); /* Y */ + else + atomic_long_inc(raw_cpu_ptr(&scp->srcu_locks)); /* Z */ + barrier(); /* Avoid leaking the critical section. */ + return scp; +} + +/* + * Removes the count for the old reader from the appropriate + * per-CPU element of the srcu_struct. Note that this may well be a + * different CPU than that which was incremented by the corresponding + * srcu_read_lock_fast(), but it must be within the same task. + * + * Note that both this_cpu_inc() and atomic_long_inc() are RCU read-side + * critical sections either because they disables interrupts, because they + * are a single instruction, or because they are a read-modify-write atomic + * operation, depending on the whims of the architecture. + * + * This means that __srcu_read_unlock_fast() is not all that fast + * on architectures that support NMIs but do not supply NMI-safe + * implementations of this_cpu_inc(). + */ +static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) +{ + barrier(); /* Avoid leaking the critical section. */ + if (!IS_ENABLED(CONFIG_NEED_SRCU_NMI_SAFE)) + this_cpu_inc(scp->srcu_unlocks.counter); /* Z */ + else + atomic_long_inc(raw_cpu_ptr(&scp->srcu_unlocks)); /* Z */ + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_fast()."); +} + +/* + * Counts the new reader in the appropriate per-CPU element of the + * srcu_struct. Returns an index that must be passed to the matching + * srcu_read_unlock_lite(). + * + * Note that this_cpu_inc() is an RCU read-side critical section either + * because it disables interrupts, because it is a single instruction, + * or because it is a read-modify-write atomic operation, depending on + * the whims of the architecture. + */ +static inline int __srcu_read_lock_lite(struct srcu_struct *ssp) +{ + struct srcu_ctr __percpu *scp = READ_ONCE(ssp->srcu_ctrp); + + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_lite()."); + this_cpu_inc(scp->srcu_locks.counter); /* Y */ + barrier(); /* Avoid leaking the critical section. */ + return __srcu_ptr_to_ctr(ssp, scp); +} + +/* + * Removes the count for the old reader from the appropriate + * per-CPU element of the srcu_struct. Note that this may well be a + * different CPU than that which was incremented by the corresponding + * srcu_read_lock_lite(), but it must be within the same task. + * + * Note that this_cpu_inc() is an RCU read-side critical section either + * because it disables interrupts, because it is a single instruction, + * or because it is a read-modify-write atomic operation, depending on + * the whims of the architecture. + */ +static inline void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx) +{ + barrier(); /* Avoid leaking the critical section. */ + this_cpu_inc(__srcu_ctr_to_ptr(ssp, idx)->srcu_unlocks.counter); /* Z */ + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlock_lite()."); +} + +void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor); + +// Record reader usage even for CONFIG_PROVE_RCU=n kernels. This is +// needed only for flavors that require grace-period smp_mb() calls to be +// promoted to synchronize_rcu(). +static inline void srcu_check_read_flavor_force(struct srcu_struct *ssp, int read_flavor) +{ + struct srcu_data *sdp = raw_cpu_ptr(ssp->sda); + + if (likely(READ_ONCE(sdp->srcu_reader_flavor) & read_flavor)) + return; + + // Note that the cmpxchg() in __srcu_check_read_flavor() is fully ordered. + __srcu_check_read_flavor(ssp, read_flavor); +} + +// Record non-_lite() usage only for CONFIG_PROVE_RCU=y kernels. +static inline void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) +{ + if (IS_ENABLED(CONFIG_PROVE_RCU)) + __srcu_check_read_flavor(ssp, read_flavor); +} + #endif |