On 11/06, Nam Cao wrote: > > @@ -534,6 +517,23 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, > ppid = task_tgid_nr_ns(task->real_parent, ns); > pgid = task_pgrp_nr_ns(task, ns); > > + /* > + * esp and eip are intentionally zeroed out. There is no > + * non-racy way to read them without freezing the task. > + * Programs that need reliable values can use ptrace(2). OK, but then: > + * The only exception is if the task is core dumping because > + * a program is not able to use ptrace(2) in that case. It is > + * safe because the task has stopped executing permanently. > + */ > + if (permitted && task->signal->core_state) { > + if (try_get_task_stack(task)) { > + eip = KSTK_EIP(task); > + esp = KSTK_ESP(task); > + put_task_stack(task); How can the task->signal->core_state check help ? Suppose we have a task T1 with T1-pid == 100 and you read /proc/100/stat. It is possible that the T1's sub-thread T2 starts the coredumping and sets signal->core_state != NULL. But read(/proc/100/stat) can run before T1 gets SIGKILL from T2 and enters the kernel mode? Oleg.