diff options
Diffstat (limited to 'src/include/qemu/rcu.h')
| -rw-r--r-- | src/include/qemu/rcu.h | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/src/include/qemu/rcu.h b/src/include/qemu/rcu.h new file mode 100644 index 0000000..0d9f677 --- /dev/null +++ b/src/include/qemu/rcu.h @@ -0,0 +1,156 @@ +#ifndef QEMU_RCU_H +#define QEMU_RCU_H + +/* + * urcu-mb.h + * + * Userspace RCU header with explicit memory barrier. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + * + * IBM's contributions to this file may be relicensed under LGPLv2 or later. + */ + +#include <stdlib.h> +#include <assert.h> +#include <limits.h> +#include <unistd.h> +#include <stdint.h> +#include <stdbool.h> +#include <glib.h> + +#include "qemu/compiler.h" +#include "qemu/thread.h" +#include "qemu/queue.h" +#include "qemu/atomic.h" + +#ifdef __cplusplus +extern "C" { +#endif + +/* + * Important ! + * + * Each thread containing read-side critical sections must be registered + * with rcu_register_thread() before calling rcu_read_lock(). + * rcu_unregister_thread() should be called before the thread exits. + */ + +#ifdef DEBUG_RCU +#define rcu_assert(args...) assert(args) +#else +#define rcu_assert(args...) +#endif + +/* + * Global quiescent period counter with low-order bits unused. + * Using a int rather than a char to eliminate false register dependencies + * causing stalls on some architectures. + */ +extern unsigned long rcu_gp_ctr; + +extern QemuEvent rcu_gp_event; + +struct rcu_reader_data { + /* Data used by both reader and synchronize_rcu() */ + unsigned long ctr; + bool waiting; + + /* Data used by reader only */ + unsigned depth; + + /* Data used for registry, protected by rcu_registry_lock */ + QLIST_ENTRY(rcu_reader_data) node; +}; + +extern __thread struct rcu_reader_data rcu_reader; + +static inline void rcu_read_lock(void) +{ + struct rcu_reader_data *p_rcu_reader = &rcu_reader; + unsigned ctr; + + if (p_rcu_reader->depth++ > 0) { + return; + } + + ctr = atomic_read(&rcu_gp_ctr); + atomic_xchg(&p_rcu_reader->ctr, ctr); + if (atomic_read(&p_rcu_reader->waiting)) { + atomic_set(&p_rcu_reader->waiting, false); + qemu_event_set(&rcu_gp_event); + } +} + +static inline void rcu_read_unlock(void) +{ + struct rcu_reader_data *p_rcu_reader = &rcu_reader; + + assert(p_rcu_reader->depth != 0); + if (--p_rcu_reader->depth > 0) { + return; + } + + atomic_xchg(&p_rcu_reader->ctr, 0); + if (atomic_read(&p_rcu_reader->waiting)) { + atomic_set(&p_rcu_reader->waiting, false); + qemu_event_set(&rcu_gp_event); + } +} + +extern void synchronize_rcu(void); + +/* + * Reader thread registration. + */ +extern void rcu_register_thread(void); +extern void rcu_unregister_thread(void); +extern void rcu_after_fork(void); + +struct rcu_head; +typedef void RCUCBFunc(struct rcu_head *head); + +struct rcu_head { + struct rcu_head *next; + RCUCBFunc *func; +}; + +extern void call_rcu1(struct rcu_head *head, RCUCBFunc *func); + +/* The operands of the minus operator must have the same type, + * which must be the one that we specify in the cast. + */ +#define call_rcu(head, func, field) \ + call_rcu1(({ \ + char __attribute__((unused)) \ + offset_must_be_zero[-offsetof(__typeof__(*(head)), field)], \ + func_type_invalid = (func) - (void (*)(__typeof__(head)))(func); \ + &(head)->field; \ + }), \ + (RCUCBFunc *)(func)) + +#define g_free_rcu(obj, field) \ + call_rcu1(({ \ + char __attribute__((unused)) \ + offset_must_be_zero[-offsetof(__typeof__(*(obj)), field)]; \ + &(obj)->field; \ + }), \ + (RCUCBFunc *)g_free); + +#ifdef __cplusplus +} +#endif + +#endif /* QEMU_RCU_H */ |
