diff options
Diffstat (limited to 'include/linux/srcutree.h')
| -rw-r--r-- | include/linux/srcutree.h | 67 |
1 files changed, 66 insertions, 1 deletions
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index ed57598394de..490aeecc6bb4 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -25,7 +25,7 @@ struct srcu_data { /* Read-side state. */ atomic_long_t srcu_lock_count[2]; /* Locks per CPU. */ atomic_long_t srcu_unlock_count[2]; /* Unlocks per CPU. */ - int srcu_nmi_safety; /* NMI-safe srcu_struct structure? */ + int srcu_reader_flavor; /* Reader flavor for srcu_struct structure? */ /* Update-side state. */ spinlock_t __private lock ____cacheline_internodealigned_in_smp; @@ -43,6 +43,11 @@ struct srcu_data { struct srcu_struct *ssp; }; +/* Values for ->srcu_reader_flavor. */ +#define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock(). +#define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe(). +#define SRCU_READ_FLAVOR_LITE 0x4 // srcu_read_lock_lite(). + /* * Node in SRCU combining tree, similar in function to rcu_data. */ @@ -204,4 +209,64 @@ 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); +/* + * 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) +{ + int idx; + + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_lite()."); + idx = READ_ONCE(ssp->srcu_idx) & 0x1; + this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter); /* Y */ + barrier(); /* Avoid leaking the critical section. */ + return idx; +} + +/* + * 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(ssp->sda->srcu_unlock_count[idx].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 _lite() usage even for CONFIG_PROVE_RCU=n kernels. +static inline void srcu_check_read_flavor_lite(struct srcu_struct *ssp) +{ + struct srcu_data *sdp = raw_cpu_ptr(ssp->sda); + + if (likely(READ_ONCE(sdp->srcu_reader_flavor) & SRCU_READ_FLAVOR_LITE)) + return; + + // Note that the cmpxchg() in srcu_check_read_flavor() is fully ordered. + __srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_LITE); +} + +// 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 |