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2a96a552f9
This reverts commit a59629fcc6.
This is not needed anymore because the IOThread mutex is not
"magic" anymore (need not kick the CPU thread)and also because
fork callbacks are only enabled at the very beginning of
QEMU's execution.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
150 lines
4.2 KiB
C
150 lines
4.2 KiB
C
#ifndef QEMU_RCU_H
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#define QEMU_RCU_H
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/*
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* urcu-mb.h
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*
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* Userspace RCU header with explicit memory barrier.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* IBM's contributions to this file may be relicensed under LGPLv2 or later.
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*/
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#include "qemu/thread.h"
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#include "qemu/queue.h"
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#include "qemu/atomic.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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* Important !
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*
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* Each thread containing read-side critical sections must be registered
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* with rcu_register_thread() before calling rcu_read_lock().
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* rcu_unregister_thread() should be called before the thread exits.
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*/
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#ifdef DEBUG_RCU
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#define rcu_assert(args...) assert(args)
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#else
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#define rcu_assert(args...)
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#endif
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/*
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* Global quiescent period counter with low-order bits unused.
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* Using a int rather than a char to eliminate false register dependencies
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* causing stalls on some architectures.
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*/
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extern unsigned long rcu_gp_ctr;
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extern QemuEvent rcu_gp_event;
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struct rcu_reader_data {
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/* Data used by both reader and synchronize_rcu() */
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unsigned long ctr;
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bool waiting;
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/* Data used by reader only */
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unsigned depth;
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/* Data used for registry, protected by rcu_registry_lock */
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QLIST_ENTRY(rcu_reader_data) node;
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};
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extern __thread struct rcu_reader_data rcu_reader;
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static inline void rcu_read_lock(void)
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{
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struct rcu_reader_data *p_rcu_reader = &rcu_reader;
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unsigned ctr;
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if (p_rcu_reader->depth++ > 0) {
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return;
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}
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ctr = atomic_read(&rcu_gp_ctr);
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atomic_xchg(&p_rcu_reader->ctr, ctr);
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}
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static inline void rcu_read_unlock(void)
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{
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struct rcu_reader_data *p_rcu_reader = &rcu_reader;
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assert(p_rcu_reader->depth != 0);
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if (--p_rcu_reader->depth > 0) {
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return;
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}
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atomic_xchg(&p_rcu_reader->ctr, 0);
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if (unlikely(atomic_read(&p_rcu_reader->waiting))) {
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atomic_set(&p_rcu_reader->waiting, false);
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qemu_event_set(&rcu_gp_event);
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}
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}
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extern void synchronize_rcu(void);
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/*
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* Reader thread registration.
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*/
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extern void rcu_register_thread(void);
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extern void rcu_unregister_thread(void);
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/*
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* Support for fork(). fork() support is enabled at startup.
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*/
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extern void rcu_enable_atfork(void);
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extern void rcu_disable_atfork(void);
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struct rcu_head;
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typedef void RCUCBFunc(struct rcu_head *head);
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struct rcu_head {
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struct rcu_head *next;
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RCUCBFunc *func;
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};
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extern void call_rcu1(struct rcu_head *head, RCUCBFunc *func);
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/* The operands of the minus operator must have the same type,
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* which must be the one that we specify in the cast.
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*/
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#define call_rcu(head, func, field) \
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call_rcu1(({ \
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char __attribute__((unused)) \
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offset_must_be_zero[-offsetof(typeof(*(head)), field)], \
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func_type_invalid = (func) - (void (*)(typeof(head)))(func); \
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&(head)->field; \
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}), \
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(RCUCBFunc *)(func))
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#define g_free_rcu(obj, field) \
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call_rcu1(({ \
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char __attribute__((unused)) \
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offset_must_be_zero[-offsetof(typeof(*(obj)), field)]; \
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&(obj)->field; \
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}), \
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(RCUCBFunc *)g_free);
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#ifdef __cplusplus
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}
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#endif
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#endif /* QEMU_RCU_H */
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