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[Qemu-devel] [PATCH 07/12] rcu: allow nested calls to rcu_thread_offline
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PATCH 07/12] rcu: allow nested calls to rcu_thread_offline/rcu_thread_online |
Date: |
Wed, 15 May 2013 17:48:52 +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 d7c4f0b..4e7cde3 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 e43b912..3a55045 100644
--- a/include/qemu/rcu.h
+++ b/include/qemu/rcu.h
@@ -77,6 +77,9 @@ 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;
};
@@ -127,9 +130,14 @@ static inline void rcu_read_unlock(void)
static inline void rcu_quiescent_state(void)
{
struct rcu_reader_data *p_rcu_reader = 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);
@@ -141,6 +149,10 @@ static inline void rcu_thread_offline(void)
{
struct rcu_reader_data *p_rcu_reader = 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);
@@ -150,7 +162,12 @@ static inline void rcu_thread_offline(void)
static inline void rcu_thread_online(void)
{
- rcu_quiescent_state();
+ struct rcu_reader_data *p_rcu_reader = 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 06/12] rcu: add rcutorture, (continued)
- [Qemu-devel] [PATCH 06/12] rcu: add rcutorture, Paolo Bonzini, 2013/05/15
- [Qemu-devel] [PATCH 09/12] event loop: report RCU quiescent states, Paolo Bonzini, 2013/05/15
- [Qemu-devel] [PATCH 08/12] qemu-thread: report RCU quiescent states, Paolo Bonzini, 2013/05/15
- [Qemu-devel] [PATCH 10/12] cpus: report RCU quiescent states, Paolo Bonzini, 2013/05/15
- [Qemu-devel] [PATCH 01/12] add a header file for atomic operations, Paolo Bonzini, 2013/05/15
- [Qemu-devel] [PATCH 11/12] block: report RCU quiescent states, Paolo Bonzini, 2013/05/15
- [Qemu-devel] [PATCH 12/12] migration: report RCU quiescent states, Paolo Bonzini, 2013/05/15
- [Qemu-devel] [PATCH 07/12] rcu: allow nested calls to rcu_thread_offline/rcu_thread_online,
Paolo Bonzini <=
- Re: [Qemu-devel] [RFC PATCH 00/12] RCU implementation for QEMU, Peter Maydell, 2013/05/15
- Re: [Qemu-devel] [RFC PATCH 00/12] RCU implementation for QEMU, Peter Maydell, 2013/05/15
- Re: [Qemu-devel] [RFC PATCH 00/12] RCU implementation for QEMU, Peter Maydell, 2013/05/15