On (10/24/12 20:52), Oleg Nesterov wrote:
> On 10/24, Sergey Senozhatsky wrote:
> >
> > On (10/24/12 20:06), Oleg Nesterov wrote:
> > > On 10/24, Sergey Senozhatsky wrote:
> > > >
> > > > small question,
> > > >
> > > > ptrace_notify() and forward calls are able to both indirectly and
> > > > directly call schedule(),
> > > > /* direct call from ptrace_stop()*/,
> > > > should, in this case, rcu_user_enter() be called before
> > > > tracehook_report_syscall_exit(regs, step)
> > > > and ptrace chain?
> > >
> > > Well, I don't really understand this magic... but why?
> > >
> >
> > My understanding is (I may be wrong)
>
> Oh, I bet I have much more chances to be wrong ;)
>
> > that we can schedule() from ptrace chain to
>
> I don't understand how ptrace chain differs from, say, audit_syscall_exit().
> There is nothing special in ptrace_stop() in this respect.
>
hm.
> > some arbitrary task, which will continue its execution from the point where
> > RCU assumes
> > CPU as not idle, while CPU in fact still in idle state -- no one said
> > rcu_idle_exit()
>
> confused... of course it would be wrong if syscall_trace_leave() is
> called when CPU is considered idle,
>
sorry, I meant idle from RCU point of view:
int rcu_is_cpu_idle(void)
{
return !rcu_dynticks_nesting;
}
> > if so, does the same apply to in_user?
>
> Not sure we understand each other. But I believe that ->in_user should be
> already false when syscall_trace_leave() is called.
>
oh, my apology. I was very wrong about this.
-ss
>
> Oleg.
>
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