X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-static.h;h=30bd7fddbea5372c08aff936751e79225893a314;hp=f1aab2f2dfed0123070e3d608fec00701a3b364d;hb=3644b3ee9ca6a858cf733579012ef595d652dcdf;hpb=d2d2303563e2b260114bc0aa679d8c256eb0a43e diff --git a/urcu-static.h b/urcu-static.h index f1aab2f..30bd7fd 100644 --- a/urcu-static.h +++ b/urcu-static.h @@ -31,59 +31,18 @@ #include #include +#include +#include -#include -#include +#include +#include +#include +#include +#include -/* - * Identify a shared load. A smp_rmc() or smp_mc() should come before the load. - */ -#define _LOAD_SHARED(p) ACCESS_ONCE(p) - -/* - * Load a data from shared memory, doing a cache flush if required. - */ -#define LOAD_SHARED(p) \ - ({ \ - smp_rmc(); \ - _LOAD_SHARED(p); \ - }) - -/* - * Identify a shared store. A smp_wmc() or smp_mc() should follow the store. - */ -#define _STORE_SHARED(x, v) ({ ACCESS_ONCE(x) = (v); }) - -/* - * Store v into x, where x is located in shared memory. Performs the required - * cache flush after writing. Returns v. - */ -#define STORE_SHARED(x, v) \ - ({ \ - _STORE_SHARED(x, v); \ - smp_wmc(); \ - (v); \ - }) - -/** - * _rcu_dereference - reads (copy) a RCU-protected pointer to a local variable - * into a RCU read-side critical section. The pointer can later be safely - * dereferenced within the critical section. - * - * This ensures that the pointer copy is invariant thorough the whole critical - * section. - * - * Inserts memory barriers on architectures that require them (currently only - * Alpha) and documents which pointers are protected by RCU. - * - * Should match rcu_assign_pointer() or rcu_xchg_pointer(). - */ - -#define _rcu_dereference(p) ({ \ - typeof(p) _________p1 = LOAD_SHARED(p); \ - smp_read_barrier_depends(); \ - (_________p1); \ - }) +#define futex(...) syscall(__NR_futex, __VA_ARGS__) +#define FUTEX_WAIT 0 +#define FUTEX_WAKE 1 /* * This code section can only be included in LGPL 2.1 compatible source code. @@ -108,6 +67,17 @@ */ #define KICK_READER_LOOPS 10000 +/* + * Active attempts to check for reader Q.S. before calling futex(). + */ +#define RCU_QS_ACTIVE_ATTEMPTS 100 + +#ifdef DEBUG_RCU +#define rcu_assert(args...) assert(args) +#else +#define rcu_assert(args...) +#endif + #ifdef DEBUG_YIELD #include #include @@ -117,8 +87,11 @@ #define YIELD_READ (1 << 0) #define YIELD_WRITE (1 << 1) -/* Updates without DEBUG_FULL_MB are much slower. Account this in the delay */ -#ifdef DEBUG_FULL_MB +/* + * Updates without URCU_MB are much slower. Account this in + * the delay. + */ +#ifdef URCU_MB /* maximum sleep delay, in us */ #define MAX_SLEEP 50 #else @@ -161,7 +134,7 @@ static inline void debug_yield_init(void) } #endif -#ifdef DEBUG_FULL_MB +#ifdef URCU_MB static inline void reader_barrier() { smp_mb(); @@ -189,7 +162,30 @@ static inline void reader_barrier() */ extern long urcu_gp_ctr; -extern long __thread urcu_active_readers; +struct urcu_reader { + /* Data used by both reader and synchronize_rcu() */ + long ctr; + char need_mb; + /* Data used for registry */ + struct list_head head __attribute__((aligned(CACHE_LINE_SIZE))); + pthread_t tid; +}; + +extern struct urcu_reader __thread urcu_reader; + +extern int gp_futex; + +/* + * Wake-up waiting synchronize_rcu(). Called from many concurrent threads. + */ +static inline void wake_up_gp(void) +{ + if (unlikely(uatomic_read(&gp_futex) == -1)) { + uatomic_set(&gp_futex, 0); + futex(&gp_futex, FUTEX_WAKE, 1, + NULL, NULL, 0); + } +} static inline int rcu_old_gp_ongoing(long *value) { @@ -210,81 +206,38 @@ static inline void _rcu_read_lock(void) { long tmp; - tmp = urcu_active_readers; + tmp = urcu_reader.ctr; /* urcu_gp_ctr = RCU_GP_COUNT | (~RCU_GP_CTR_BIT or RCU_GP_CTR_BIT) */ - /* - * The data dependency "read urcu_gp_ctr, write urcu_active_readers", - * serializes those two memory operations. The memory barrier in the - * signal handler ensures we receive the proper memory commit barriers - * required by _STORE_SHARED and _LOAD_SHARED whenever communication - * with the writer is needed. - */ - if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) - _STORE_SHARED(urcu_active_readers, _LOAD_SHARED(urcu_gp_ctr)); - else - _STORE_SHARED(urcu_active_readers, tmp + RCU_GP_COUNT); - /* - * Increment active readers count before accessing the pointer. - * See force_mb_all_threads(). - */ - reader_barrier(); + if (likely(!(tmp & RCU_GP_CTR_NEST_MASK))) { + _STORE_SHARED(urcu_reader.ctr, _LOAD_SHARED(urcu_gp_ctr)); + /* + * Set active readers count for outermost nesting level before + * accessing the pointer. See force_mb_all_threads(). + */ + reader_barrier(); + } else { + _STORE_SHARED(urcu_reader.ctr, tmp + RCU_GP_COUNT); + } } static inline void _rcu_read_unlock(void) { - reader_barrier(); + long tmp; + + tmp = urcu_reader.ctr; /* * Finish using rcu before decrementing the pointer. * See force_mb_all_threads(). */ - _STORE_SHARED(urcu_active_readers, urcu_active_readers - RCU_GP_COUNT); + if (likely((tmp & RCU_GP_CTR_NEST_MASK) == RCU_GP_COUNT)) { + reader_barrier(); + _STORE_SHARED(urcu_reader.ctr, urcu_reader.ctr - RCU_GP_COUNT); + /* write urcu_reader.ctr before read futex */ + reader_barrier(); + wake_up_gp(); + } else { + _STORE_SHARED(urcu_reader.ctr, urcu_reader.ctr - RCU_GP_COUNT); + } } -/** - * _rcu_assign_pointer - assign (publicize) a pointer to a new data structure - * meant to be read by RCU read-side critical sections. Returns the assigned - * value. - * - * Documents which pointers will be dereferenced by RCU read-side critical - * sections and adds the required memory barriers on architectures requiring - * them. It also makes sure the compiler does not reorder code initializing the - * data structure before its publication. - * - * Should match rcu_dereference_pointer(). - */ - -#define _rcu_assign_pointer(p, v) \ - ({ \ - if (!__builtin_constant_p(v) || \ - ((v) != NULL)) \ - wmb(); \ - STORE_SHARED(p, v); \ - }) - -/** - * _rcu_xchg_pointer - same as rcu_assign_pointer, but returns the previous - * pointer to the data structure, which can be safely freed after waitin for a - * quiescent state using synchronize_rcu(). - */ - -#define _rcu_xchg_pointer(p, v) \ - ({ \ - if (!__builtin_constant_p(v) || \ - ((v) != NULL)) \ - wmb(); \ - xchg(p, v); \ - }) - -/* - * Exchanges the pointer and waits for quiescent state. - * The pointer returned can be freed. - */ -#define _rcu_publish_content(p, v) \ - ({ \ - void *oldptr; \ - oldptr = _rcu_xchg_pointer(p, v); \ - synchronize_rcu(); \ - oldptr; \ - }) - #endif /* _URCU_STATIC_H */