[Qemu-devel] [PATCH v6 2/4] monitor: protect mon->fds with mon_lock

[Peter Xu <peterx@redhat.com>]

mon->fds were protected by BQL.  Now protect it by mon_lock so that it
can even be used in monitor iothread.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 monitor.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/monitor.c b/monitor.c
index 14c681dc8a..d6c3c08932 100644
--- a/monitor.c
+++ b/monitor.c
@@ -213,7 +213,6 @@ struct Monitor {
     BlockCompletionFunc *password_completion_cb;
     void *password_opaque;
     mon_cmd_t *cmd_table;
-    QLIST_HEAD(,mon_fd_t) fds;
     QTAILQ_ENTRY(Monitor) entry;
 
     /*
@@ -225,6 +224,7 @@ struct Monitor {
     /*
      * Fields that are protected by the per-monitor lock.
      */
+    QLIST_HEAD(, mon_fd_t) fds;
     QString *outbuf;
     guint out_watch;
     /* Read under either BQL or mon_lock, written with BQL+mon_lock.  */
@@ -2189,7 +2189,7 @@ static void hmp_acl_remove(Monitor *mon, const QDict *qdict)
 void qmp_getfd(const char *fdname, Error **errp)
 {
     mon_fd_t *monfd;
-    int fd;
+    int fd, tmp_fd;
 
     fd = qemu_chr_fe_get_msgfd(&cur_mon->chr);
     if (fd == -1) {
@@ -2204,13 +2204,17 @@ void qmp_getfd(const char *fdname, Error **errp)
         return;
     }
 
+    qemu_mutex_lock(&cur_mon->mon_lock);
     QLIST_FOREACH(monfd, &cur_mon->fds, next) {
         if (strcmp(monfd->name, fdname) != 0) {
             continue;
         }
 
-        close(monfd->fd);
+        tmp_fd = monfd->fd;
         monfd->fd = fd;
+        qemu_mutex_unlock(&cur_mon->mon_lock);
+        /* Make sure close() is out of critical section */
+        close(tmp_fd);
         return;
     }
 
@@ -2219,24 +2223,31 @@ void qmp_getfd(const char *fdname, Error **errp)
     monfd->fd = fd;
 
     QLIST_INSERT_HEAD(&cur_mon->fds, monfd, next);
+    qemu_mutex_unlock(&cur_mon->mon_lock);
 }
 
 void qmp_closefd(const char *fdname, Error **errp)
 {
     mon_fd_t *monfd;
+    int tmp_fd;
 
+    qemu_mutex_lock(&cur_mon->mon_lock);
     QLIST_FOREACH(monfd, &cur_mon->fds, next) {
         if (strcmp(monfd->name, fdname) != 0) {
             continue;
         }
 
         QLIST_REMOVE(monfd, next);
-        close(monfd->fd);
+        tmp_fd = monfd->fd;
         g_free(monfd->name);
         g_free(monfd);
+        qemu_mutex_unlock(&cur_mon->mon_lock);
+        /* Make sure close() is out of critical section */
+        close(tmp_fd);
         return;
     }
 
+    qemu_mutex_unlock(&cur_mon->mon_lock);
     error_setg(errp, QERR_FD_NOT_FOUND, fdname);
 }
 
@@ -2244,6 +2255,7 @@ int monitor_get_fd(Monitor *mon, const char *fdname, Error **errp)
 {
     mon_fd_t *monfd;
 
+    qemu_mutex_lock(&mon->mon_lock);
     QLIST_FOREACH(monfd, &mon->fds, next) {
         int fd;
 
@@ -2257,10 +2269,12 @@ int monitor_get_fd(Monitor *mon, const char *fdname, Error **errp)
         QLIST_REMOVE(monfd, next);
         g_free(monfd->name);
         g_free(monfd);
+        qemu_mutex_unlock(&mon->mon_lock);
 
         return fd;
     }
 
+    qemu_mutex_unlock(&mon->mon_lock);
     error_setg(errp, "File descriptor named '%s' has not been found", fdname);
     return -1;
 }
-- 
2.17.0