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authorJosé Pekkarinen <jose.pekkarinen@nokia.com>2016-05-18 13:18:31 +0300
committerJosé Pekkarinen <jose.pekkarinen@nokia.com>2016-05-18 13:42:15 +0300
commit437fd90c0250dee670290f9b714253671a990160 (patch)
treeb871786c360704244a07411c69fb58da9ead4a06 /qemu/util/rcu.c
parent5bbd6fe9b8bab2a93e548c5a53b032d1939eec05 (diff)
These changes are the raw update to qemu-2.6.
Collission happened in the following patches: migration: do cleanup operation after completion(738df5b9) Bug fix.(1750c932f86) kvmclock: add a new function to update env->tsc.(b52baab2) The code provided by the patches was already in the upstreamed version. Change-Id: I3cc11841a6a76ae20887b2e245710199e1ea7f9a Signed-off-by: José Pekkarinen <jose.pekkarinen@nokia.com>
Diffstat (limited to 'qemu/util/rcu.c')
-rw-r--r--qemu/util/rcu.c54
1 files changed, 36 insertions, 18 deletions
diff --git a/qemu/util/rcu.c b/qemu/util/rcu.c
index cdcad678b..bceb3e472 100644
--- a/qemu/util/rcu.c
+++ b/qemu/util/rcu.c
@@ -26,12 +26,8 @@
* IBM's contributions to this file may be relicensed under LGPLv2 or later.
*/
+#include "qemu/osdep.h"
#include "qemu-common.h"
-#include <stdio.h>
-#include <assert.h>
-#include <stdlib.h>
-#include <stdint.h>
-#include <errno.h>
#include "qemu/rcu.h"
#include "qemu/atomic.h"
#include "qemu/thread.h"
@@ -47,7 +43,8 @@
unsigned long rcu_gp_ctr = RCU_GP_LOCKED;
QemuEvent rcu_gp_event;
-static QemuMutex rcu_gp_lock;
+static QemuMutex rcu_registry_lock;
+static QemuMutex rcu_sync_lock;
/*
* Check whether a quiescent state was crossed between the beginning of
@@ -66,7 +63,7 @@ static inline int rcu_gp_ongoing(unsigned long *ctr)
*/
__thread struct rcu_reader_data rcu_reader;
-/* Protected by rcu_gp_lock. */
+/* Protected by rcu_registry_lock. */
typedef QLIST_HEAD(, rcu_reader_data) ThreadList;
static ThreadList registry = QLIST_HEAD_INITIALIZER(registry);
@@ -114,10 +111,26 @@ static void wait_for_readers(void)
break;
}
- /* Wait for one thread to report a quiescent state and
- * try again.
+ /* Wait for one thread to report a quiescent state and try again.
+ * Release rcu_registry_lock, so rcu_(un)register_thread() doesn't
+ * wait too much time.
+ *
+ * rcu_register_thread() may add nodes to &registry; it will not
+ * wake up synchronize_rcu, but that is okay because at least another
+ * thread must exit its RCU read-side critical section before
+ * synchronize_rcu is done. The next iteration of the loop will
+ * move the new thread's rcu_reader from &registry to &qsreaders,
+ * because rcu_gp_ongoing() will return false.
+ *
+ * rcu_unregister_thread() may remove nodes from &qsreaders instead
+ * of &registry if it runs during qemu_event_wait. That's okay;
+ * the node then will not be added back to &registry by QLIST_SWAP
+ * below. The invariant is that the node is part of one list when
+ * rcu_registry_lock is released.
*/
+ qemu_mutex_unlock(&rcu_registry_lock);
qemu_event_wait(&rcu_gp_event);
+ qemu_mutex_lock(&rcu_registry_lock);
}
/* put back the reader list in the registry */
@@ -126,7 +139,8 @@ static void wait_for_readers(void)
void synchronize_rcu(void)
{
- qemu_mutex_lock(&rcu_gp_lock);
+ qemu_mutex_lock(&rcu_sync_lock);
+ qemu_mutex_lock(&rcu_registry_lock);
if (!QLIST_EMPTY(&registry)) {
/* In either case, the atomic_mb_set below blocks stores that free
@@ -149,7 +163,8 @@ void synchronize_rcu(void)
wait_for_readers();
}
- qemu_mutex_unlock(&rcu_gp_lock);
+ qemu_mutex_unlock(&rcu_registry_lock);
+ qemu_mutex_unlock(&rcu_sync_lock);
}
@@ -273,23 +288,24 @@ void call_rcu1(struct rcu_head *node, void (*func)(struct rcu_head *node))
void rcu_register_thread(void)
{
assert(rcu_reader.ctr == 0);
- qemu_mutex_lock(&rcu_gp_lock);
+ qemu_mutex_lock(&rcu_registry_lock);
QLIST_INSERT_HEAD(&registry, &rcu_reader, node);
- qemu_mutex_unlock(&rcu_gp_lock);
+ qemu_mutex_unlock(&rcu_registry_lock);
}
void rcu_unregister_thread(void)
{
- qemu_mutex_lock(&rcu_gp_lock);
+ qemu_mutex_lock(&rcu_registry_lock);
QLIST_REMOVE(&rcu_reader, node);
- qemu_mutex_unlock(&rcu_gp_lock);
+ qemu_mutex_unlock(&rcu_registry_lock);
}
static void rcu_init_complete(void)
{
QemuThread thread;
- qemu_mutex_init(&rcu_gp_lock);
+ qemu_mutex_init(&rcu_registry_lock);
+ qemu_mutex_init(&rcu_sync_lock);
qemu_event_init(&rcu_gp_event, true);
qemu_event_init(&rcu_call_ready_event, false);
@@ -306,12 +322,14 @@ static void rcu_init_complete(void)
#ifdef CONFIG_POSIX
static void rcu_init_lock(void)
{
- qemu_mutex_lock(&rcu_gp_lock);
+ qemu_mutex_lock(&rcu_sync_lock);
+ qemu_mutex_lock(&rcu_registry_lock);
}
static void rcu_init_unlock(void)
{
- qemu_mutex_unlock(&rcu_gp_lock);
+ qemu_mutex_unlock(&rcu_registry_lock);
+ qemu_mutex_unlock(&rcu_sync_lock);
}
#endif