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[Qemu-devel] [PATCH 12/30] rcu: allow nested calls to rcu_thread_offline
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 12/30] rcu: allow nested calls to rcu_thread_offline/rcu_thread_online |
Date: |
Fri, 28 Jun 2013 20:26:31 +0200 |
Signed-off-by: Paolo Bonzini <address@hidden>
---
docs/rcu.txt | 5 +++++
include/qemu/rcu.h | 21 +++++++++++++++++++--
2 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/docs/rcu.txt b/docs/rcu.txt
index ca1c099..a3510b9 100644
--- a/docs/rcu.txt
+++ b/docs/rcu.txt
@@ -187,6 +187,11 @@ Marking quiescent states is done with the following three
APIs:
thread.
+rcu_thread_offline() and rcu_thread_online() can be nested. The end of
+the extended quiescent state will coincide with the outermost call to
+rcu_thread_online().
+
+
The following APIs can be used to use RCU in a thread that is not
created with qemu_thread_create():
diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h
index 1ed70bb..eff6d1e 100644
--- a/include/qemu/rcu.h
+++ b/include/qemu/rcu.h
@@ -78,6 +78,9 @@ struct rcu_reader_data {
unsigned long ctr;
bool waiting;
+ /* Data used by reader only */
+ unsigned offline;
+
/* Data used for registry, protected by rcu_gp_lock */
QLIST_ENTRY(rcu_reader_data) node;
};
@@ -100,9 +103,14 @@ static inline void rcu_read_unlock(void)
static inline void rcu_quiescent_state(void)
{
struct rcu_reader_data *p_rcu_reader = tls_get_rcu_reader();
+ unsigned ctr;
+
+ if (p_rcu_reader->offline > 0) {
+ return;
+ }
/* Reuses smp_rmb() in the last rcu_read_unlock(). */
- unsigned ctr = atomic_read(&rcu_gp_ctr);
+ 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);
@@ -114,6 +122,10 @@ static inline void rcu_thread_offline(void)
{
struct rcu_reader_data *p_rcu_reader = tls_get_rcu_reader();
+ if (p_rcu_reader->offline++ > 0) {
+ return;
+ }
+
atomic_xchg(&p_rcu_reader->ctr, 0);
if (atomic_read(&p_rcu_reader->waiting)) {
atomic_set(&p_rcu_reader->waiting, false);
@@ -123,7 +135,12 @@ static inline void rcu_thread_offline(void)
static inline void rcu_thread_online(void)
{
- rcu_quiescent_state();
+ struct rcu_reader_data *p_rcu_reader = tls_get_rcu_reader();
+
+ assert(p_rcu_reader->offline != 0);
+ if (--p_rcu_reader->offline == 0) {
+ rcu_quiescent_state();
+ }
}
extern void synchronize_rcu(void);
--
1.8.1.4
- [Qemu-devel] [PATCH 00/30] Memory API changes for 1.6: RCU-protected address space dispatch, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 01/30] memory: access FlatView from a local variable, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 02/30] memory: use a new FlatView pointer on every topology update, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 03/30] memory: add reference counting to FlatView, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 04/30] add a header file for atomic operations, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 05/30] exec: do not use qemu/tls.h, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 07/30] qemu-thread: add QemuEvent, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 06/30] qemu-thread: add TLS wrappers, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 09/30] qemu-thread: register threads with RCU, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 12/30] rcu: allow nested calls to rcu_thread_offline/rcu_thread_online,
Paolo Bonzini <=
- [Qemu-devel] [PATCH 11/30] rcu: add rcutorture, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 13/30] qemu-thread: report RCU quiescent states, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 08/30] rcu: add rcu library, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 14/30] event loop: report RCU quiescent states, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 10/30] rcu: add call_rcu, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 15/30] cpus: report RCU quiescent states, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 16/30] block: report RCU quiescent states, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 17/30] migration: report RCU quiescent states, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 19/30] memory: avoid ref/unref in memory_region_find, Paolo Bonzini, 2013/06/28
- [Qemu-devel] [PATCH 18/30] memory: protect current_map by RCU, Paolo Bonzini, 2013/06/28