lkml.org 
[lkml]   [2018]   [Jul]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v9 4/7] tracepoint: Make rcuidle tracepoint callers use SRCU
On Wed, Jul 11, 2018 at 09:00:03AM -0400, Steven Rostedt wrote:
> On Wed, 11 Jul 2018 14:49:54 +0200
> Peter Zijlstra <peterz@infradead.org> wrote:
>
> > On Thu, Jun 28, 2018 at 11:21:46AM -0700, Joel Fernandes wrote:
> > > - it_func_ptr = rcu_dereference_sched((tp)->funcs); \
> >
> > I would convert to rcu_dereference_raw() to appease sparse. The fancy
> > stuff below is pointless if you then turn off all checking.
>
> The problem with doing this is if we use a trace event without the
> proper _idle() or whatever, we wont get a warning that it is used
> incorrectly with lockdep. Or does lockdep still check if "rcu is
> watching" with rcu_dereference_raw()?

No lockdep checking is done by rcu_dereference_raw().

Thanx, Paul

> -- Steve
>
> >
> > > + \
> > > + /* \
> > > + * For rcuidle callers, use srcu since sched-rcu \
> > > + * doesn't work from the idle path. \
> > > + */ \
> > > + if (rcuidle) { \
> > > + if (in_nmi()) { \
> > > + WARN_ON_ONCE(1); \
> > > + return; /* no srcu from nmi */ \
> > > + } \
> > > + \
> > > + idx = srcu_read_lock_notrace(&tracepoint_srcu); \
> > > + it_func_ptr = \
> > > + srcu_dereference_notrace((tp)->funcs, \
> > > + &tracepoint_srcu); \
> > > + /* To keep it consistent with !rcuidle path */ \
> > > + preempt_disable_notrace(); \
> > > + } else { \
> > > + rcu_read_lock_sched_notrace(); \
> > > + it_func_ptr = \
> > > + rcu_dereference_sched((tp)->funcs); \
> > > + } \
>

\
 
 \ /
  Last update: 2018-07-11 16:26    [W:0.126 / U:2.412 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site