This commit makes CONFIG_PROVE_RCU=y kernels enforce the new rule that srcu_struct structures that are passed to srcu_read_lock_fast() and other SRCU-fast read-side markers be either initialized with init_srcu_struct_fast() on the one hand or defined with DEFINE_SRCU_FAST() or DEFINE_STATIC_SRCU_FAST() on the other.
This eliminates the read-side test that was formerly included in srcu_read_lock_fast() and friends, speeding these primitives up by about 25% (admittedly only about half of a nanosecond, but when tracing on fastpaths...) Signed-off-by: Paul E. McKenney <[email protected]> Cc: Mathieu Desnoyers <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Sebastian Andrzej Siewior <[email protected]> Cc: <[email protected]> --- include/linux/srcu.h | 6 +++--- include/linux/srcutiny.h | 1 - include/linux/srcutree.h | 16 +--------------- 3 files changed, 4 insertions(+), 19 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 2982b5a6930f..41e27c1d917d 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -297,7 +297,7 @@ static inline struct srcu_ctr __percpu *srcu_read_lock_fast(struct srcu_struct * struct srcu_ctr __percpu *retval; RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock_fast()."); - srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); retval = __srcu_read_lock_fast(ssp); rcu_try_lock_acquire(&ssp->dep_map); return retval; @@ -312,7 +312,7 @@ static inline struct srcu_ctr __percpu *srcu_read_lock_fast_notrace(struct srcu_ { struct srcu_ctr __percpu *retval; - srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); retval = __srcu_read_lock_fast(ssp); return retval; } @@ -333,7 +333,7 @@ static inline struct srcu_ctr __percpu *srcu_down_read_fast(struct srcu_struct * { WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && in_nmi()); RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_down_read_fast()."); - srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); return __srcu_read_lock_fast(ssp); } diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index 92e6ab53398f..1ecc3393fb26 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -112,7 +112,6 @@ static inline void srcu_barrier(struct srcu_struct *ssp) static inline void srcu_expedite_current(struct srcu_struct *ssp) { } #define srcu_check_read_flavor(ssp, read_flavor) do { } while (0) -#define srcu_check_read_flavor_force(ssp, read_flavor) do { } while (0) /* Defined here to avoid size increase for non-torture kernels. */ static inline void srcu_torture_stats_print(struct srcu_struct *ssp, diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 7ff4a11bc5a3..6080a9094618 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -307,21 +307,7 @@ __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp) 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. +// Record SRCU-reader usage type 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)) -- 2.40.1
