fs: mqueue: Fix file_mq_open() for SMP

Summary:
- I noticed that sometimes mqueue_test in ostest failed
  (i.e. mq_open failed) with rv-virt:smp.
- This commit fixes this issue by replacing sched_lock with
  critical section.

Impact:
- file_mq_open()

Testing:
- Tested with ostest on QEMU-7.1

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

fs/mqueue/mq_open.c

@@ -162,6 +162,7 @@ static int file_mq_vopen(FAR struct file *mq, FAR const char *mq_name,
   FAR struct mq_attr *attr = NULL;
   struct inode_search_s desc;
   char fullpath[MAX_MQUEUE_PATH];
+  irqstate_t flags;
   mode_t mode = 0;
   int ret;
 
@@ -210,11 +211,12 @@ static int file_mq_vopen(FAR struct file *mq, FAR const char *mq_name,
 
   /* Make sure that the check for the existence of the message queue
    * and the creation of the message queue are atomic with respect to
-   * other processes executing mq_open().  A simple sched_lock() should
+   * other processes executing mq_open().  A simple sched_lock() would
-   * be sufficient.
+   * be sufficient for non-SMP case but critical section is needed for
+   * SMP case.
    */
 
-  sched_lock();
+  flags = enter_critical_section();
 
   /* Get the inode for this mqueue.  This should succeed if the message
    * queue has already been created.  In this case, inode_find() will
@@ -322,7 +324,7 @@ static int file_mq_vopen(FAR struct file *mq, FAR const char *mq_name,
     }
 
   RELEASE_SEARCH(&desc);
-  sched_unlock();
+  leave_critical_section(flags);
   return OK;
 
 errout_with_inode:
@@ -330,7 +332,7 @@ errout_with_inode:
 
 errout_with_lock:
   RELEASE_SEARCH(&desc);
-  sched_unlock();
+  leave_critical_section(flags);
 
 errout:
   return ret;