From: Oleg Nesterov Since the patch "Fix ptrace_attach()/ptrace_traceme()/de_thread() race" commit f5b40e363ad6041a96e3da32281d8faa191597b9 we set PT_ATTACHED and change child->parent "atomically" wrt task_list lock. This means we can remove the checks like "PT_ATTACHED && ->parent != ptracer" which were needed to catch the "ptrace attach is in progress" case. We can also remove the flag itself since nobody else uses it. Signed-off-by: Oleg Nesterov Cc: Roland McGrath Cc: Christoph Hellwig Signed-off-by: Andrew Morton --- include/linux/ptrace.h | 1 - kernel/exit.c | 13 +------------ kernel/ptrace.c | 6 ++---- kernel/signal.c | 5 ----- 4 files changed, 3 insertions(+), 22 deletions(-) diff -puN include/linux/ptrace.h~kill-pt_attached include/linux/ptrace.h --- a/include/linux/ptrace.h~kill-pt_attached +++ a/include/linux/ptrace.h @@ -67,7 +67,6 @@ #define PT_TRACE_EXEC 0x00000080 #define PT_TRACE_VFORK_DONE 0x00000100 #define PT_TRACE_EXIT 0x00000200 -#define PT_ATTACHED 0x00000400 /* parent != real_parent */ #define PT_TRACE_MASK 0x000003f4 diff -puN kernel/exit.c~kill-pt_attached kernel/exit.c --- a/kernel/exit.c~kill-pt_attached +++ a/kernel/exit.c @@ -1512,18 +1512,7 @@ static int wait_task_continued(struct ta static inline int my_ptrace_child(struct task_struct *p) { - if (!(p->ptrace & PT_PTRACED)) - return 0; - if (!(p->ptrace & PT_ATTACHED)) - return 1; - /* - * This child was PTRACE_ATTACH'd. We should be seeing it only if - * we are the attacher. If we are the real parent, this is a race - * inside ptrace_attach. It is waiting for the tasklist_lock, - * which we have to switch the parent links, but has already set - * the flags in p->ptrace. - */ - return (p->parent != p->real_parent); + return p->ptrace & PT_PTRACED; } static long do_wait(pid_t pid, int options, struct siginfo __user *infop, diff -puN kernel/ptrace.c~kill-pt_attached kernel/ptrace.c --- a/kernel/ptrace.c~kill-pt_attached +++ a/kernel/ptrace.c @@ -100,8 +100,7 @@ int ptrace_check_attach(struct task_stru */ read_lock(&tasklist_lock); if ((child->ptrace & PT_PTRACED) && child->parent == current && - (!(child->ptrace & PT_ATTACHED) || child->real_parent != current) - && child->signal != NULL) { + child->signal != NULL) { ret = 0; spin_lock_irq(&child->sighand->siglock); if (is_task_stopped(child)) @@ -200,8 +199,7 @@ repeat: goto bad; /* Go */ - task->ptrace |= PT_PTRACED | ((task->real_parent != current) - ? PT_ATTACHED : 0); + task->ptrace |= PT_PTRACED; if (capable(CAP_SYS_PTRACE)) task->ptrace |= PT_PTRACE_CAP; diff -puN kernel/signal.c~kill-pt_attached kernel/signal.c --- a/kernel/signal.c~kill-pt_attached +++ a/kernel/signal.c @@ -1555,11 +1555,6 @@ static inline int may_ptrace_stop(void) { if (!likely(current->ptrace & PT_PTRACED)) return 0; - - if (unlikely(current->parent == current->real_parent && - (current->ptrace & PT_ATTACHED))) - return 0; - /* * Are we in the middle of do_coredump? * If so and our tracer is also part of the coredump stopping _