PR9947: move runtime cleanup out of the work queue

The kernel lockdep checking found a possible deadlock if a forced rmmod
tried to destroy _stp_work_queue at the same time that the work queue
was unregistering tracepoints.  An unlikely scenario, but still
possible.

Now the work queue will just issue a STP_REQUEST_EXIT down to usermode,
and usermode will echo back an STP_EXIT that triggers the actual probe
cleanup.  This way the unregistrations are happening in exactly the same
context as the registrations were.

1 files changed, 6 insertions, 1 deletions

diff --git a/runtime/transport/control.c b/runtime/transport/control.c
index edde244d..680d7306 100644
--- a/runtime/transport/control.c
+++ b/runtime/transport/control.c
@@ -13,6 +13,8 @@ static _stp_mempool_t *_stp_pool_q;
 static struct list_head _stp_ctl_ready_q;
 static DEFINE_SPINLOCK(_stp_ctl_ready_lock);
 
+static void _stp_cleanup_and_exit(int send_exit);
+
 static ssize_t _stp_ctl_write_cmd(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 {
 	u32 type;
@@ -46,7 +48,7 @@ static ssize_t _stp_ctl_write_cmd(struct file *file, const char __user *buf, siz
 		}
 		break;
 	case STP_EXIT:
-		_stp_exit_flag = 1;
+		_stp_cleanup_and_exit(1);
 		break;
 	case STP_BULK:
 #ifdef STP_BULKMODE
@@ -93,6 +95,9 @@ static void _stp_ctl_write_dbug(int type, void *data, int len)
 	case STP_TRANSPORT:
 		_dbug("sending STP_TRANSPORT\n");
 		break;
+	case STP_REQUEST_EXIT:
+		_dbug("sending STP_REQUEST_EXIT\n");
+		break;
 	default:
 		_dbug("ERROR: unknown message type: %d\n", type);
 		break;