[Qemu-devel] [PATCH 2/4] coroutine: Add CoRwlock support

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 qemu-coroutine-lock.c |   44 ++++++++++++++++++++++++++++++++++++++++++++
 qemu-coroutine.h      |   12 ++++++++++++
 2 files changed, 56 insertions(+), 0 deletions(-)

diff --git a/qemu-coroutine-lock.c b/qemu-coroutine-lock.c
index 5071fb8..5ecaa94 100644
--- a/qemu-coroutine-lock.c
+++ b/qemu-coroutine-lock.c
@@ -115,3 +115,47 @@ void qemu_co_mutex_unlock(CoMutex *mutex)
 
     trace_qemu_co_mutex_unlock_return(mutex, self);
 }
+
+void qemu_co_rwlock_init(CoRwlock *lock)
+{
+    memset(lock, 0, sizeof(*lock));
+    qemu_co_queue_init(&lock->queue);
+}
+
+void qemu_co_rwlock_rdlock(CoRwlock *lock)
+{
+    while (lock->writer) {
+        qemu_co_queue_wait(&lock->queue);
+    }
+    lock->reader++;
+}
+
+void qemu_co_rwlock_unlock(CoRwlock *lock)
+{
+    assert(qemu_in_coroutine());
+    if (lock->writer) {
+        lock->writer--;;
+        assert(lock->writer == 0);
+        while (!qemu_co_queue_empty(&lock->queue)) {
+            /*
+             * Wakeup every body. This will include some
+             * writers too.
+             */
+            qemu_co_queue_next(&lock->queue);
+        }
+    } else {
+        lock->reader--;
+        assert(lock->reader >= 0);
+        /* Wakeup only one waiting writer */
+        qemu_co_queue_next(&lock->queue);
+    }
+}
+
+void qemu_co_rwlock_wrlock(CoRwlock *lock)
+{
+    while (lock->writer || lock->reader) {
+        qemu_co_queue_wait(&lock->queue);
+    }
+    lock->writer++;
+    assert(lock->writer == 1);
+}
diff --git a/qemu-coroutine.h b/qemu-coroutine.h
index 71cfa5a..a9735fb 100644
--- a/qemu-coroutine.h
+++ b/qemu-coroutine.h
@@ -17,6 +17,7 @@
 #include <stdbool.h>
 
 #include "qemu-queue.h"
+#include "qemu-thread.h"
 
 /**
  * Coroutines are a mechanism for stack switching and can be used for
@@ -114,4 +115,15 @@ void qemu_co_mutex_init(CoMutex *mutex);
 void qemu_co_mutex_lock(CoMutex *mutex);
 void qemu_co_mutex_unlock(CoMutex *mutex);
 
+typedef struct CoRwlock {
+    bool writer;
+    int reader;
+    CoQueue queue;
+} CoRwlock;
+
+void qemu_co_rwlock_init(CoRwlock *lock);
+void qemu_co_rwlock_rdlock(CoRwlock *lock);
+void qemu_co_rwlock_wrlock(CoRwlock *lock);
+void qemu_co_rwlock_unlock(CoRwlock *lock);
+
 #endif /* QEMU_COROUTINE_H */
-- 
1.7.4.1