X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-qsbr.c;h=553029578a210383df955fb384d6102ad807d51e;hp=b7c42fdb0c35deb37e8c5d76a4593746206df0d9;hb=1f689e13ea7e519b1afc001e9c55a7b1b60b599f;hpb=16aa9ee87cf4364921c36025359be01390338d87 diff --git a/urcu-qsbr.c b/urcu-qsbr.c index b7c42fd..5530295 100644 --- a/urcu-qsbr.c +++ b/urcu-qsbr.c @@ -23,31 +23,45 @@ * IBM's contributions to this file may be relicensed under LGPLv2 or later. */ +#define _GNU_SOURCE +#define _LGPL_SOURCE #include #include #include #include #include +#include #include #include #include +#include "urcu/wfqueue.h" +#include "urcu/map/urcu-qsbr.h" #define BUILD_QSBR_LIB -#include "urcu-qsbr-static.h" +#include "urcu/static/urcu-qsbr.h" +#include "urcu-pointer.h" + /* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */ +#undef _LGPL_SOURCE #include "urcu-qsbr.h" +#define _LGPL_SOURCE void __attribute__((destructor)) rcu_exit(void); static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER; -int gp_futex; +int32_t gp_futex; /* * Global grace period counter. */ unsigned long rcu_gp_ctr = RCU_GP_ONLINE; +/* + * Active attempts to check for reader Q.S. before calling futex(). + */ +#define RCU_QS_ACTIVE_ATTEMPTS 100 + /* * Written to only by each individual reader. Read by both the reader and the * writers. @@ -112,19 +126,20 @@ static void update_counter_and_wait(void) int wait_loops = 0; struct rcu_reader *index, *tmp; -#if (BITS_PER_LONG < 64) +#if (CAA_BITS_PER_LONG < 64) /* Switch parity: 0 -> 1, 1 -> 0 */ - CAA_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR); -#else /* !(BITS_PER_LONG < 64) */ + CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR); +#else /* !(CAA_BITS_PER_LONG < 64) */ /* Increment current G.P. */ - CAA_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr + RCU_GP_CTR); -#endif /* !(BITS_PER_LONG < 64) */ + CMM_STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr + RCU_GP_CTR); +#endif /* !(CAA_BITS_PER_LONG < 64) */ /* - * Must commit rcu_gp_ctr update to memory before waiting for quiescent - * state. Failure to do so could result in the writer waiting forever - * while new readers are always accessing data (no progress). Enforce - * compiler-order of store to rcu_gp_ctr before load rcu_reader ctr. + * Must commit rcu_gp_ctr update to memory before waiting for + * quiescent state. Failure to do so could result in the writer + * waiting forever while new readers are always accessing data + * (no progress). Enforce compiler-order of store to rcu_gp_ctr + * before load rcu_reader ctr. */ cmm_barrier(); @@ -140,26 +155,33 @@ static void update_counter_and_wait(void) */ for (;;) { wait_loops++; - if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { - uatomic_dec(&gp_futex); + if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { + uatomic_set(&gp_futex, -1); + /* + * Write futex before write waiting (the other side + * reads them in the opposite order). + */ + cmm_smp_wmb(); + cds_list_for_each_entry(index, ®istry, node) { + _CMM_STORE_SHARED(index->waiting, 1); + } /* Write futex before read reader_gp */ cmm_smp_mb(); } - cds_list_for_each_entry_safe(index, tmp, ®istry, node) { if (!rcu_gp_ongoing(&index->ctr)) cds_list_move(&index->node, &qsreaders); } if (cds_list_empty(®istry)) { - if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { + if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { /* Read reader_gp before write futex */ cmm_smp_mb(); uatomic_set(&gp_futex, 0); } break; } else { - if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) { + if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) { wait_gp(); } else { #ifndef HAS_INCOHERENT_CACHES @@ -179,7 +201,7 @@ static void update_counter_and_wait(void) * long-size to ensure we do not encounter an overflow bug. */ -#if (BITS_PER_LONG < 64) +#if (CAA_BITS_PER_LONG < 64) void synchronize_rcu(void) { unsigned long was_online; @@ -187,18 +209,17 @@ void synchronize_rcu(void) was_online = rcu_reader.ctr; /* All threads should read qparity before accessing data structure - * where new ptr points to. - */ - /* Write new ptr before changing the qparity */ - cmm_smp_mb(); - - /* + * where new ptr points to. In the "then" case, rcu_thread_offline + * includes a memory barrier. + * * Mark the writer thread offline to make sure we don't wait for - * our own quiescent state. This allows using synchronize_rcu() in - * threads registered as readers. + * our own quiescent state. This allows using synchronize_rcu() + * in threads registered as readers. */ if (was_online) - CAA_STORE_SHARED(rcu_reader.ctr, 0); + rcu_thread_offline(); + else + cmm_smp_mb(); mutex_lock(&rcu_gp_lock); @@ -212,10 +233,11 @@ void synchronize_rcu(void) /* * Must finish waiting for quiescent state for parity 0 before - * committing next rcu_gp_ctr update to memory. Failure to do so could - * result in the writer waiting forever while new readers are always - * accessing data (no progress). Enforce compiler-order of load - * rcu_reader ctr before store to rcu_gp_ctr. + * committing next rcu_gp_ctr update to memory. Failure to + * do so could result in the writer waiting forever while new + * readers are always accessing data (no progress). Enforce + * compiler-order of load rcu_reader ctr before store to + * rcu_gp_ctr. */ cmm_barrier(); @@ -238,10 +260,11 @@ out: * freed. */ if (was_online) - _CAA_STORE_SHARED(rcu_reader.ctr, CAA_LOAD_SHARED(rcu_gp_ctr)); - cmm_smp_mb(); + rcu_thread_online(); + else + cmm_smp_mb(); } -#else /* !(BITS_PER_LONG < 64) */ +#else /* !(CAA_BITS_PER_LONG < 64) */ void synchronize_rcu(void) { unsigned long was_online; @@ -250,12 +273,13 @@ void synchronize_rcu(void) /* * Mark the writer thread offline to make sure we don't wait for - * our own quiescent state. This allows using synchronize_rcu() in - * threads registered as readers. + * our own quiescent state. This allows using synchronize_rcu() + * in threads registered as readers. */ - cmm_smp_mb(); if (was_online) - CAA_STORE_SHARED(rcu_reader.ctr, 0); + rcu_thread_offline(); + else + cmm_smp_mb(); mutex_lock(&rcu_gp_lock); if (cds_list_empty(®istry)) @@ -265,10 +289,11 @@ out: mutex_unlock(&rcu_gp_lock); if (was_online) - _CAA_STORE_SHARED(rcu_reader.ctr, CAA_LOAD_SHARED(rcu_gp_ctr)); - cmm_smp_mb(); + rcu_thread_online(); + else + cmm_smp_mb(); } -#endif /* !(BITS_PER_LONG < 64) */ +#endif /* !(CAA_BITS_PER_LONG < 64) */ /* * library wrappers to be used by non-LGPL compatible source code. @@ -324,5 +349,12 @@ void rcu_unregister_thread(void) void rcu_exit(void) { - assert(cds_list_empty(®istry)); + /* + * Assertion disabled because call_rcu threads are now rcu + * readers, and left running at exit. + * assert(cds_list_empty(®istry)); + */ } + +#include "urcu-call-rcu-impl.h" +#include "urcu-defer-impl.h"