Messages in this thread | | | Date | Thu, 19 May 2011 12:34:12 +0200 | From | Tejun Heo <> | Subject | Re: [PATCH 03/10] ptrace: implement PTRACE_SEIZE |
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Hello,
On Wed, May 18, 2011 at 08:17:56PM +0200, Oleg Nesterov wrote: > On 05/16, Tejun Heo wrote: > > > > @@ -315,6 +338,9 @@ static int ptrace_attach(struct task_struct *task) > > if (task_is_stopped(task)) { > > task->jobctl |= JOBCTL_TRAP_STOP | JOBCTL_TRAPPING; > > signal_wake_up(task, 1); > > + } else if (seize) { > > + task->jobctl |= JOBCTL_TRAP_STOP; > > So, this can race with do_signal_stop(), it can clear TRAP_STOP and > JOBCTL_STOP_PENDING can guarantee the tracee will trap later.
Confused. How can do_signal_stop() clear TRAP_STOP?
> > + * When PT_SEIZED, it's used for both group stop and explicit > > + * SEIZE/INTERRUPT traps. Both generate PTRACE_EVENT_STOP trap > > + * with accompanying siginfo. > > + * > > + * When !PT_SEIZED, it's used only for group stop trap with > > + * CLD_STOPPED as exit_code and no siginfo. > > */ > > if (unlikely(current->jobctl & JOBCTL_TRAP_MASK)) { > > - signr = current->jobctl & JOBCTL_STOP_SIGMASK; > > - WARN_ON_ONCE(!signr); > > - ptrace_stop(signr, CLD_STOPPED, 0, NULL); > > - current->exit_code = 0; > > + if (current->ptrace & PT_SEIZED) { > > + ptrace_do_notify(SIGTRAP | PTRACE_EVENT_STOP << 8, > > + CLD_STOPPED); > > So. When PT_SEIZED, we always report PTRACE_EVENT_STOP and PTRACE_GET_SIGINFO > always works. > > Personally I agree, this looks more clean and natural.
Yeah, I like it much better. INTERRUPT trap and group stop trap being separate while sharing some attributes was disturbing.
Thanks.
-- tejun
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