lkml.org 
[lkml]   [2011]   [May]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH 10/10] ptrace: implement group stop notification for ptracer
Date
On Thursday 19 May 2011 19:13, Oleg Nesterov wrote:
> On 05/19, Tejun Heo wrote:
> > On Thu, May 19, 2011 at 06:32:46PM +0200, Oleg Nesterov wrote:
> > > > +static void ptrace_trap_notify(struct task_struct *t)
> > > > +{
> > > > + siginfo_t *si = t->last_siginfo;
> > > > +
> > > > + WARN_ON_ONCE(!(t->ptrace & PT_SEIZED));
> > > > + assert_spin_locked(&t->sighand->siglock);
> > > > +
> > > > + /*
> > > > + * @t is being ptraced and new SEIZE behavior is in effect.
> > > > + * Schedule sticky trap which will clear on the next GETSIGINFO.
> > > > + */
> > > > + t->jobctl |= JOBCTL_TRAP_NOTIFY;
> > >
> > > This is also set by do_signal_stop(). Cleared by PTRACE_GETSIGINFO.
> > >
> > > How can this work? Doesn't this mean PTRACE_GETSIGINFO becomes mandatory
> > > before PTRACE_CONT? IOW, unless the tracee does PTRACE_GETSIGINFO to clear
> > > this bit, PTRACE_CONT just leads to another trap, no?
> >
> > Yes, group stop state change raises a sticky trap condition which is
> > cleared by GETSIGINFO.
>
> Hmm. At least now I understand the meaining what "sticky" means in
> this discussion ;) I was confused.

I still don't see why is it needed. Userspace API doesn't require it.

Are you trying to solve/simplify something on the kernel side with it?

--
vda


\
 
 \ /
  Last update: 2011-05-20 00:51    [W:0.108 / U:35.796 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site