[PATCH 5/6] co-shared-resource: protect with a mutex

[Emanuele Giuseppe Esposito <eesposit@redhat.com>]

co-shared-resource is currently not thread-safe, as also reported
in co-shared-resource.h. Add a QemuMutex because co_try_get_from_shres
can also be invoked from non-coroutine context.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 util/qemu-co-shared-resource.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/util/qemu-co-shared-resource.c b/util/qemu-co-shared-resource.c
index 1c83cd9d29..c455d02a1e 100644
--- a/util/qemu-co-shared-resource.c
+++ b/util/qemu-co-shared-resource.c
@@ -32,6 +32,7 @@ struct SharedResource {
     uint64_t available;
 
     CoQueue queue;
+    QemuMutex lock;
 };
 
 SharedResource *shres_create(uint64_t total)
@@ -40,17 +41,23 @@ SharedResource *shres_create(uint64_t total)
 
     s->total = s->available = total;
     qemu_co_queue_init(&s->queue);
+    qemu_mutex_init(&s->lock);
 
     return s;
 }
 
 void shres_destroy(SharedResource *s)
 {
-    assert(s->available == s->total);
+    WITH_QEMU_LOCK_GUARD(&s->lock) {
+        assert(s->available == s->total);
+    }
+
+    qemu_mutex_destroy(&s->lock);
     g_free(s);
 }
 
-bool co_try_get_from_shres(SharedResource *s, uint64_t n)
+/* Called with lock held */
+static bool co_try_get_from_shres_unlocked(SharedResource *s, uint64_t n)
 {
     if (s->available >= n) {
         s->available -= n;
@@ -60,16 +67,27 @@ bool co_try_get_from_shres(SharedResource *s, uint64_t n)
     return false;
 }
 
+bool co_try_get_from_shres(SharedResource *s, uint64_t n)
+{
+    bool res;
+    QEMU_LOCK_GUARD(&s->lock);
+    res = co_try_get_from_shres_unlocked(s, n);
+
+    return res;
+}
+
 void coroutine_fn co_get_from_shres(SharedResource *s, uint64_t n)
 {
+    QEMU_LOCK_GUARD(&s->lock);
     assert(n <= s->total);
-    while (!co_try_get_from_shres(s, n)) {
-        qemu_co_queue_wait(&s->queue, NULL);
+    while (!co_try_get_from_shres_unlocked(s, n)) {
+        qemu_co_queue_wait(&s->queue, &s->lock);
     }
 }
 
 void coroutine_fn co_put_to_shres(SharedResource *s, uint64_t n)
 {
+    QEMU_LOCK_GUARD(&s->lock);
     assert(s->total - s->available >= n);
     s->available += n;
     qemu_co_queue_restart_all(&s->queue);
-- 
2.30.2