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SubjectRe: [PATCH 27/34] rcu: Use CONFIG_PREEMPTION where appropriate
On Tue, Oct 15, 2019 at 09:18:14PM +0200, Sebastian Andrzej Siewior wrote:
> The config option `CONFIG_PREEMPT' is used for the preemption model
> "Low-Latency Desktop". The config option `CONFIG_PREEMPTION' is enabled
> when kernel preemption is enabled which is true for the preemption model
> `CONFIG_PREEMPT' and `CONFIG_PREEMPT_RT'.
>
> Use `CONFIG_PREEMPTION' if it applies to both preemption models and not
> just to `CONFIG_PREEMPT'.
>
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
> Cc: Joel Fernandes <joel@joelfernandes.org>
> Cc: Davidlohr Bueso <dave@stgolabs.net>
> Cc: rcu@vger.kernel.org
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

This one does apply, so I have queued it for review and testing, thank you!

Thanx, Paul

> ---
> include/linux/rcupdate.h | 4 ++--
> kernel/rcu/Kconfig | 4 ++--
> kernel/rcu/rcutorture.c | 2 +-
> kernel/rcu/srcutiny.c | 2 +-
> kernel/rcu/tree.c | 4 ++--
> kernel/rcu/tree_exp.h | 2 +-
> kernel/rcu/tree_plugin.h | 4 ++--
> 7 files changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 75a2eded7aa2c..1e3dad252d61f 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -154,7 +154,7 @@ static inline void exit_tasks_rcu_finish(void) { }
> *
> * This macro resembles cond_resched(), except that it is defined to
> * report potential quiescent states to RCU-tasks even if the cond_resched()
> - * machinery were to be shut off, as some advocate for PREEMPT kernels.
> + * machinery were to be shut off, as some advocate for PREEMPTION kernels.
> */
> #define cond_resched_tasks_rcu_qs() \
> do { \
> @@ -580,7 +580,7 @@ do { \
> *
> * You can avoid reading and understanding the next paragraph by
> * following this rule: don't put anything in an rcu_read_lock() RCU
> - * read-side critical section that would block in a !PREEMPT kernel.
> + * read-side critical section that would block in a !PREEMPTION kernel.
> * But if you want the full story, read on!
> *
> * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU),
> diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
> index 7644eda17d624..01b56177464d8 100644
> --- a/kernel/rcu/Kconfig
> +++ b/kernel/rcu/Kconfig
> @@ -200,8 +200,8 @@ config RCU_NOCB_CPU
> specified at boot time by the rcu_nocbs parameter. For each
> such CPU, a kthread ("rcuox/N") will be created to invoke
> callbacks, where the "N" is the CPU being offloaded, and where
> - the "p" for RCU-preempt (PREEMPT kernels) and "s" for RCU-sched
> - (!PREEMPT kernels). Nothing prevents this kthread from running
> + the "p" for RCU-preempt (PREEMPTION kernels) and "s" for RCU-sched
> + (!PREEMPTION kernels). Nothing prevents this kthread from running
> on the specified CPUs, but (1) the kthreads may be preempted
> between each callback, and (2) affinity or cgroups can be used
> to force the kthreads to run on whatever set of CPUs is desired.
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index 3c9feca1eab17..c070d103f34d6 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -1725,7 +1725,7 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
> // Give the scheduler a chance, even on nohz_full CPUs.
> static void rcu_torture_fwd_prog_cond_resched(unsigned long iter)
> {
> - if (IS_ENABLED(CONFIG_PREEMPT) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {
> + if (IS_ENABLED(CONFIG_PREEMPTION) && IS_ENABLED(CONFIG_NO_HZ_FULL)) {
> // Real call_rcu() floods hit userspace, so emulate that.
> if (need_resched() || (iter & 0xfff))
> schedule();
> diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
> index 44d6606b83257..6208c1dae5c95 100644
> --- a/kernel/rcu/srcutiny.c
> +++ b/kernel/rcu/srcutiny.c
> @@ -103,7 +103,7 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock);
>
> /*
> * Workqueue handler to drive one grace period and invoke any callbacks
> - * that become ready as a result. Single-CPU and !PREEMPT operation
> + * that become ready as a result. Single-CPU and !PREEMPTION operation
> * means that we get away with murder on synchronization. ;-)
> */
> void srcu_drive_gp(struct work_struct *wp)
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 81105141b6a82..1c5de816ae9e5 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -2667,9 +2667,9 @@ EXPORT_SYMBOL_GPL(kfree_call_rcu);
>
> /*
> * During early boot, any blocking grace-period wait automatically
> - * implies a grace period. Later on, this is never the case for PREEMPT.
> + * implies a grace period. Later on, this is never the case for PREEMPTION.
> *
> - * Howevr, because a context switch is a grace period for !PREEMPT, any
> + * Howevr, because a context switch is a grace period for !PREEMPTION, any
> * blocking grace-period wait automatically implies a grace period if
> * there is only one CPU online at any point time during execution of
> * either synchronize_rcu() or synchronize_rcu_expedited(). It is OK to
> diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
> index d632cd0195975..98d078cafa5a6 100644
> --- a/kernel/rcu/tree_exp.h
> +++ b/kernel/rcu/tree_exp.h
> @@ -670,7 +670,7 @@ static void rcu_exp_handler(void *unused)
> }
> }
>
> -/* PREEMPT=y, so no PREEMPT=n expedited grace period to clean up after. */
> +/* PREEMPTION=y, so no PREEMPTION=n expedited grace period to clean up after. */
> static void sync_sched_exp_online_cleanup(int cpu)
> {
> }
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 2defc7fe74c39..e6c987d171cbe 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -788,7 +788,7 @@ static void __init rcu_bootup_announce(void)
> }
>
> /*
> - * Note a quiescent state for PREEMPT=n. Because we do not need to know
> + * Note a quiescent state for PREEMPTION=n. Because we do not need to know
> * how many quiescent states passed, just if there was at least one since
> * the start of the grace period, this just sets a flag. The caller must
> * have disabled preemption.
> @@ -838,7 +838,7 @@ void rcu_all_qs(void)
> EXPORT_SYMBOL_GPL(rcu_all_qs);
>
> /*
> - * Note a PREEMPT=n context switch. The caller must have disabled interrupts.
> + * Note a PREEMPTION=n context switch. The caller must have disabled interrupts.
> */
> void rcu_note_context_switch(bool preempt)
> {
> --
> 2.23.0
>

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