Add comment to reflect that we should retry after thread singling failed.

1 files changed, 4 insertions, 0 deletions

diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c
index 859612b..0817845 100644
--- a/sys/kern/kern_exit.c
+++ b/sys/kern/kern_exit.c
@@ -153,6 +153,10 @@ retry:
 		 * to return to userland will thread_exit() from userret().
 		 * thread_exit() will unsuspend us when the last other
 		 * thread exits.
+		 * If there is already a thread singler after resumption,
+		 * calling thread_single will fail, in the case, we just
+		 * re-check all suspension request, the thread should
+		 * either be suspended there or exit.
 		 */
 		if (thread_single(SINGLE_EXIT))
 			goto retry;