exit: wait: don't use zombie->real_parent

[firefly-linux-kernel-4.4.55.git] / kernel / exit.c

diff --git a/kernel/exit.c b/kernel/exit.c
index 9c9526d8727663d9c1a4f7802527929f47f185c7..457673d659346ed230c1c99f775afed2fa1ed539 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -973,8 +973,7 @@ static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
  */
 static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
 {
-       unsigned long state;
-       int retval, status, traced;
+       int state, retval, status;
        pid_t pid = task_pid_vnr(p);
        uid_t uid = from_kuid_munged(current_user_ns(), task_uid(p));
        struct siginfo __user *infop;
@@ -999,21 +998,20 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
                }
                return wait_noreap_copyout(wo, p, pid, uid, why, status);
        }
-
-       traced = ptrace_reparented(p);
        /*
         * Move the task's state to DEAD/TRACE, only one thread can do this.
         */
-       state = traced && thread_group_leader(p) ? EXIT_TRACE : EXIT_DEAD;
+       state = (ptrace_reparented(p) && thread_group_leader(p)) ?
+               EXIT_TRACE : EXIT_DEAD;
        if (cmpxchg(&p->exit_state, EXIT_ZOMBIE, state) != EXIT_ZOMBIE)
                return 0;
+
        /*
-        * It can be ptraced but not reparented, check
-        * thread_group_leader() to filter out sub-threads.
+        * Check thread_group_leader() to exclude the traced sub-threads.
         */
-       if (likely(!traced) && thread_group_leader(p)) {
-               struct signal_struct *psig;
-               struct signal_struct *sig;
+       if (state == EXIT_DEAD && thread_group_leader(p)) {
+               struct signal_struct *sig = p->signal;
+               struct signal_struct *psig = current->signal;
                unsigned long maxrss;
                cputime_t tgutime, tgstime;
 
@@ -1025,21 +1023,20 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
                 * accumulate in the parent's signal_struct c* fields.
                 *
                 * We don't bother to take a lock here to protect these
-                * p->signal fields, because they are only touched by
-                * __exit_signal, which runs with tasklist_lock
-                * write-locked anyway, and so is excluded here.  We do
-                * need to protect the access to parent->signal fields,
-                * as other threads in the parent group can be right
-                * here reaping other children at the same time.
+                * p->signal fields because the whole thread group is dead
+                * and nobody can change them.
+                *
+                * psig->stats_lock also protects us from our sub-theads
+                * which can reap other children at the same time. Until
+                * we change k_getrusage()-like users to rely on this lock
+                * we have to take ->siglock as well.
                 *
                 * We use thread_group_cputime_adjusted() to get times for
                 * the thread group, which consolidates times for all threads
                 * in the group including the group leader.
                 */
                thread_group_cputime_adjusted(p, &tgutime, &tgstime);
-               spin_lock_irq(&p->real_parent->sighand->siglock);
-               psig = p->real_parent->signal;
-               sig = p->signal;
+               spin_lock_irq(&current->sighand->siglock);
                write_seqlock(&psig->stats_lock);
                psig->cutime += tgutime + sig->cutime;
                psig->cstime += tgstime + sig->cstime;
@@ -1064,7 +1061,7 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
                task_io_accounting_add(&psig->ioac, &p->ioac);
                task_io_accounting_add(&psig->ioac, &sig->ioac);
                write_sequnlock(&psig->stats_lock);
-               spin_unlock_irq(&p->real_parent->sighand->siglock);
+               spin_unlock_irq(&current->sighand->siglock);
        }
 
        /*