My attempt to make the comment more explicit.
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
include/linux/tracehook.h | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
--- UTRACE-PTRACE/include/linux/tracehook.h~3_NOTIFY_RESUME_MB_COMMENT
2009-12-12 16:32:39.000000000 +0100
+++ UTRACE-PTRACE/include/linux/tracehook.h 2009-12-12 17:28:03.000000000
+0100
@@ -670,9 +670,10 @@ static inline void tracehook_notify_resu
{
struct task_struct *task = current;
/*
- * This pairs with the barrier implicit in set_notify_resume().
- * It ensures that we read the nonzero utrace_flags set before
- * set_notify_resume() was called by utrace setup.
+ * If we race with attach which sets nonzero ->utrace_flags,
+ * make sure we do not read ->utrace_flags before the caller
+ * clears TIF_NOTIFY_RESUME. This pairs with the implicit mb()
+ * before setting TIF_NOTIFY_RESUME in set_notify_resume().
*/
smp_rmb();
if (task_utrace_flags(task))
