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authorKevin Wolf <kwolf@redhat.com>2020-10-05 17:58:48 +0200
committerMarkus Armbruster <armbru@redhat.com>2020-10-09 07:08:19 +0200
commite69ee454b5f9dff3af48bcfc3d9691b3edb02fe2 (patch)
tree50d13aedafd82f3efdb50a50be8bae13aa5d8379 /monitor/monitor.c
parent41725fa7eda1d97576fc8c79b58d04a61629f40e (diff)
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monitor: Make current monitor a per-coroutine property
This way, a monitor command handler will still be able to access the current monitor, but when it yields, all other code code will correctly get NULL from monitor_cur(). This uses a hash table to map the coroutine pointer to the current monitor of that coroutine. Outside of coroutine context, we associate the current monitor with the leader coroutine of the current thread. Approaches to implement some form of coroutine local storage directly in the coroutine core code have been considered and discarded because they didn't end up being much more generic than the hash table and their performance impact on coroutines not using coroutine local storage was unclear. As the block layer uses a coroutine per I/O request, this is a fast path and we have to be careful. It's safest to just stay out of this path with code only used by the monitor. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Message-Id: <20201005155855.256490-8-kwolf@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Markus Armbruster <armbru@redhat.com>
Diffstat (limited to 'monitor/monitor.c')
-rw-r--r--monitor/monitor.c34
1 files changed, 27 insertions, 7 deletions
diff --git a/monitor/monitor.c b/monitor/monitor.c
index 099c164..ef68ca9 100644
--- a/monitor/monitor.c
+++ b/monitor/monitor.c
@@ -58,29 +58,48 @@ IOThread *mon_iothread;
/* Bottom half to dispatch the requests received from I/O thread */
QEMUBH *qmp_dispatcher_bh;
-/* Protects mon_list, monitor_qapi_event_state, monitor_destroyed. */
+/*
+ * Protects mon_list, monitor_qapi_event_state, coroutine_mon,
+ * monitor_destroyed.
+ */
QemuMutex monitor_lock;
static GHashTable *monitor_qapi_event_state;
+static GHashTable *coroutine_mon; /* Maps Coroutine* to Monitor* */
MonitorList mon_list;
int mon_refcount;
static bool monitor_destroyed;
-static __thread Monitor *cur_monitor;
-
Monitor *monitor_cur(void)
{
- return cur_monitor;
+ Monitor *mon;
+
+ qemu_mutex_lock(&monitor_lock);
+ mon = g_hash_table_lookup(coroutine_mon, qemu_coroutine_self());
+ qemu_mutex_unlock(&monitor_lock);
+
+ return mon;
}
/**
* Sets a new current monitor and returns the old one.
+ *
+ * If a non-NULL monitor is set for a coroutine, another call
+ * resetting it to NULL is required before the coroutine terminates,
+ * otherwise a stale entry would remain in the hash table.
*/
-Monitor *monitor_set_cur(Monitor *mon)
+Monitor *monitor_set_cur(Coroutine *co, Monitor *mon)
{
- Monitor *old_monitor = cur_monitor;
+ Monitor *old_monitor = monitor_cur();
+
+ qemu_mutex_lock(&monitor_lock);
+ if (mon) {
+ g_hash_table_replace(coroutine_mon, co, mon);
+ } else {
+ g_hash_table_remove(coroutine_mon, co);
+ }
+ qemu_mutex_unlock(&monitor_lock);
- cur_monitor = mon;
return old_monitor;
}
@@ -623,6 +642,7 @@ void monitor_init_globals_core(void)
{
monitor_qapi_event_init();
qemu_mutex_init(&monitor_lock);
+ coroutine_mon = g_hash_table_new(NULL, NULL);
/*
* The dispatcher BH must run in the main loop thread, since we