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rcu: add call_rcu

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Asynchronous callbacks provided by call_rcu are particularly important
for QEMU, because the BQL makes it hard to use synchronize_rcu.

In addition, the current RCU implementation is not particularly friendly
to multiple concurrent synchronize_rcu callers, making call_rcu even
more important.

Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2013-05-13 17:49:24 +02:00
parent d62cb4f2fd
commit 26387f86c9
3 changed files with 247 additions and 4 deletions
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22
include/qemu/rcu.h
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@ -118,6 +118,28 @@ extern void synchronize_rcu(void);
extern void rcu_register_thread(void);
extern void rcu_unregister_thread(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))
#ifdef __cplusplus
}
#endif