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SubjectRe: [PATCH v2 0/5] ptrace-vs-PREEMPT_RT and freezer rewrite
On 2022-04-22 14:15:35 [-0500], Eric W. Biederman wrote:
> Sebastian Andrzej Siewior <bigeasy@linutronix.de> writes:
>
> > On 2022-04-21 17:02:48 [+0200], Peter Zijlstra wrote:
> >> Find here a new posting of the ptrace and freezer patches :-)
> >>
> >> The majority of the changes are in patch 2, which with much feedback from Oleg
> >> and Eric has changed lots.
> >>
> >> I'm hoping we're converging on something agreeable.
> >
> > I tested this under RT (had to remove the preempt-disable section in
> > ptrace_stop()) with ssdd [0]. It forks a few tasks and then
> > PTRACE_SINGLESTEPs them for a few iterations.
>
> Out of curiosity why did you need to remove the preempt_disable section
> on PREEMPT_RT? It should have lasted for just a moment until schedule
> was called.

within that section spinlock_t locks are acquired. These locks are
sleeping locks on PREEMPT_RT and must not be acquired within a
preempt-disable section. (A spinlock_t lock does not disable preemption
on PREEMPT_RT.)

> Eric

Sebastian

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