On Wed, Jul 31, 2024 at 06:07:32PM +0200, Frederic Weisbecker wrote:
> Le Wed, Jul 24, 2024 at 04:43:13PM +0200, Valentin Schneider a écrit :
> > The context_tracking.state RCU_DYNTICKS subvariable has been renamed to
> > RCU_WATCHING, and the 'dynticks' prefix can be dropped without losing any
> > meaning.
> >
> > While at it, flip the suffixes of these helpers. We are not telling
> > that we are entering dynticks mode from an RCU-task perspective anymore; we
> > are telling that we are exiting RCU-tasks because we are in eqs mode.
> >
> > Suggested-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
> > Signed-off-by: Valentin Schneider <vschneid@xxxxxxxxxx>
> > ---
> > kernel/context_tracking.c | 28 ++++++++++++++--------------
> > 1 file changed, 14 insertions(+), 14 deletions(-)
> >
> > diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
> > index 8262f57a43636..1c16a7336360f 100644
> > --- a/kernel/context_tracking.c
> > +++ b/kernel/context_tracking.c
> > @@ -38,24 +38,24 @@ EXPORT_SYMBOL_GPL(context_tracking);
> > #ifdef CONFIG_CONTEXT_TRACKING_IDLE
> > #define TPS(x) tracepoint_string(x)
> >
> > -/* Record the current task on dyntick-idle entry. */
> > -static __always_inline void rcu_dynticks_task_enter(void)
> > +/* Record the current task on exiting RCU-tasks (dyntick-idle entry). */
> > +static __always_inline void rcu_task_exit(void)
>
> So this makes sense.
>
> > {
> > #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
> > WRITE_ONCE(current->rcu_tasks_idle_cpu, smp_processor_id());
> > #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
> > }
> >
> > -/* Record no current task on dyntick-idle exit. */
> > -static __always_inline void rcu_dynticks_task_exit(void)
> > +/* Record no current task on entering RCU-tasks (dyntick-idle exit). */
> > +static __always_inline void rcu_task_enter(void)
>
> That too.
>
> > {
> > #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
> > WRITE_ONCE(current->rcu_tasks_idle_cpu, -1);
> > #endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
> > }
> >
> > -/* Turn on heavyweight RCU tasks trace readers on idle/user entry. */
> > -static __always_inline void rcu_dynticks_task_trace_enter(void)
> > +/* Turn on heavyweight RCU tasks trace readers on kernel exit. */
> > +static __always_inline void rcu_task_trace_exit(void)
>
> But that eventually doesn't, because it's not about not wathing anymore from
> an RCU-TASKS-TRACE perspective. It's actually about adding more heavyweight
> ordering to track down RCU-TASKS-TRACE read side while traditional RCU is not
> watching. Sorry for understanding it that late.
>
> Oh well. So a more accurate name here would be rcu_task_trace_heavyweight_enter().
>
> > {
> > #ifdef CONFIG_TASKS_TRACE_RCU
> > if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
> > @@ -63,8 +63,8 @@ static __always_inline void rcu_dynticks_task_trace_enter(void)
> > #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
> > }
> >
> > -/* Turn off heavyweight RCU tasks trace readers on idle/user exit. */
> > -static __always_inline void rcu_dynticks_task_trace_exit(void)
> > +/* Turn off heavyweight RCU tasks trace readers on kernel entry. */
> > +static __always_inline void rcu_task_trace_enter(void)
>
> And rcu_task_trace_heavyweight_exit().
>
I have updated it here [1]. Please let me know if something looks
incorrect.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/neeraj.upadhyay/linux-rcu.git/commit/?h=next.14.08.24a&id=cfc22b9f1572b137dd9f36da831dd7b69c9fe352
- Neeraj
> Thanks!
>
> > {
> > #ifdef CONFIG_TASKS_TRACE_RCU
> > if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
> > @@ -87,7 +87,7 @@ static noinstr void ct_kernel_exit_state(int offset)
> > * critical sections, and we also must force ordering with the
> > * next idle sojourn.
> > */
> > - rcu_dynticks_task_trace_enter(); // Before ->dynticks update!
> > + rcu_task_trace_exit(); // Before CT state update!
> > seq = ct_state_inc(offset);
> > // RCU is no longer watching. Better be in extended quiescent state!
> > WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & CT_RCU_WATCHING));
> > @@ -109,7 +109,7 @@ static noinstr void ct_kernel_enter_state(int offset)
> > */
> > seq = ct_state_inc(offset);
> > // RCU is now watching. Better not be in an extended quiescent state!
> > - rcu_dynticks_task_trace_exit(); // After ->dynticks update!
> > + rcu_task_trace_enter(); // After CT state update!
> > WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(seq & CT_RCU_WATCHING));
> > }
> >
> > @@ -149,7 +149,7 @@ static void noinstr ct_kernel_exit(bool user, int offset)
> > // RCU is watching here ...
> > ct_kernel_exit_state(offset);
> > // ... but is no longer watching here.
> > - rcu_dynticks_task_enter();
> > + rcu_task_exit();
> > }
> >
> > /*
> > @@ -173,7 +173,7 @@ static void noinstr ct_kernel_enter(bool user, int offset)
> > ct->nesting++;
> > return;
> > }
> > - rcu_dynticks_task_exit();
> > + rcu_task_enter();
> > // RCU is not watching here ...
> > ct_kernel_enter_state(offset);
> > // ... but is watching here.
> > @@ -240,7 +240,7 @@ void noinstr ct_nmi_exit(void)
> > // ... but is no longer watching here.
> >
> > if (!in_nmi())
> > - rcu_dynticks_task_enter();
> > + rcu_task_exit();
> > }
> >
> > /**
> > @@ -274,7 +274,7 @@ void noinstr ct_nmi_enter(void)
> > if (rcu_dynticks_curr_cpu_in_eqs()) {
> >
> > if (!in_nmi())
> > - rcu_dynticks_task_exit();
> > + rcu_task_enter();
> >
> > // RCU is not watching here ...
> > ct_kernel_enter_state(CT_RCU_WATCHING);
> > --
> > 2.43.0
> >
