Man page 9 : wait_task_stopped

wait_task_stopped - Wait for TASK_STOPPED or TASK_TRACED

int wait_task_stopped(struct wait_opts *  wo , int  ptrace , struct task_struct *  p );

wo
    wait options

ptrace
    is the wait for ptrace

p
    task to wait for

Handle sys_wait4 work for p in state TASK_STOPPED or TASK_TRACED.

read_lock(tasklist_lock), which is released if return value is non-zero. Also, grabs and releases p->sighand->siglock.

0 if wait condition didnAqt exist and search for other wait conditions should continue. Non-zero return, -errno on failure and pAqs pid on success, implies that tasklist_lock is released and wait condition search should terminate.