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Date: Tue, 15 Oct 2019 03:57:16 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Lai Jiangshan <laijs@...ux.alibaba.com>
Cc: Lai Jiangshan <jiangshanlai@...il.com>,
Joel Fernandes <joel@...lfernandes.org>,
Josh Triplett <josh@...htriplett.org>,
Steven Rostedt <rostedt@...dmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Ingo Molnar <mingo@...hat.com>,
Luis Chamberlain <mcgrof@...nel.org>,
Kees Cook <keescook@...omium.org>,
David Sterba <dsterba@...e.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Yafang Shao <laoar.shao@...il.com>,
Marco Elver <elver@...gle.com>, rcu@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v2] rcu: make PREEMPT_RCU to be a decoration of TREE_RCU
On Tue, Oct 15, 2019 at 02:55:57AM +0000, Lai Jiangshan wrote:
> Currently PREEMPT_RCU and TREE_RCU are "contrary" configs
> when they can't be both on. But PREEMPT_RCU is actually a kind
> of TREE_RCU in the implementation. It seams to be appropriate
> to make PREEMPT_RCU to be a decorative option of TREE_RCU.
>
> Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
> Signed-off-by: Lai Jiangshan <jiangshanlai@...il.com>
> Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
Applied for further review and testing, thank you both!
Thanx, Paul
> ---
> Changed from v1:
> Rebased on -rcu "dev" branch
> include/linux/rcupdate.h | 4 ++--
> include/trace/events/rcu.h | 4 ++--
> kernel/rcu/Kconfig | 13 +++++++------
> kernel/rcu/Makefile | 1 -
> kernel/rcu/rcu.h | 2 +-
> kernel/rcu/update.c | 2 +-
> kernel/sysctl.c | 2 +-
> 7 files changed, 14 insertions(+), 14 deletions(-)
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index c6351314cbe6..4dcf46985922 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -167,7 +167,7 @@ do { \
> * TREE_RCU and rcu_barrier_() primitives in TINY_RCU.
> */
>
> -#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
> +#if defined(CONFIG_TREE_RCU)
> #include <linux/rcutree.h>
> #elif defined(CONFIG_TINY_RCU)
> #include <linux/rcutiny.h>
> @@ -585,7 +585,7 @@ do { \
> * read-side critical section that would block in a !PREEMPT kernel.
> * But if you want the full story, read on!
> *
> - * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU),
> + * In non-preemptible RCU implementations (pure TREE_RCU and TINY_RCU),
> * it is illegal to block while in an RCU read-side critical section.
> * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPTION
> * kernel builds, RCU read-side critical sections may be preempted,
> diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
> index 35a384ec78b5..5e49b06e8104 100644
> --- a/include/trace/events/rcu.h
> +++ b/include/trace/events/rcu.h
> @@ -41,7 +41,7 @@ TRACE_EVENT(rcu_utilization,
> TP_printk("%s", __entry->s)
> );
>
> -#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
> +#if defined(CONFIG_TREE_RCU)
>
> /*
> * Tracepoint for grace-period events. Takes a string identifying the
> @@ -432,7 +432,7 @@ TRACE_EVENT_RCU(rcu_fqs,
> __entry->cpu, __entry->qsevent)
> );
>
> -#endif /* #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) */
> +#endif /* #if defined(CONFIG_TREE_RCU) */
>
> /*
> * Tracepoint for dyntick-idle entry/exit events. These take a string
> diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
> index 7644eda17d62..0303934e6ef0 100644
> --- a/kernel/rcu/Kconfig
> +++ b/kernel/rcu/Kconfig
> @@ -7,7 +7,7 @@ menu "RCU Subsystem"
>
> config TREE_RCU
> bool
> - default y if !PREEMPTION && SMP
> + default y if SMP
> help
> This option selects the RCU implementation that is
> designed for very large SMP system with hundreds or
> @@ -17,6 +17,7 @@ config TREE_RCU
> config PREEMPT_RCU
> bool
> default y if PREEMPTION
> + select TREE_RCU
> help
> This option selects the RCU implementation that is
> designed for very large SMP systems with hundreds or
> @@ -78,7 +79,7 @@ config TASKS_RCU
> user-mode execution as quiescent states.
>
> config RCU_STALL_COMMON
> - def_bool ( TREE_RCU || PREEMPT_RCU )
> + def_bool TREE_RCU
> help
> This option enables RCU CPU stall code that is common between
> the TINY and TREE variants of RCU. The purpose is to allow
> @@ -86,13 +87,13 @@ config RCU_STALL_COMMON
> making these warnings mandatory for the tree variants.
>
> config RCU_NEED_SEGCBLIST
> - def_bool ( TREE_RCU || PREEMPT_RCU || TREE_SRCU )
> + def_bool ( TREE_RCU || TREE_SRCU )
>
> config RCU_FANOUT
> int "Tree-based hierarchical RCU fanout value"
> range 2 64 if 64BIT
> range 2 32 if !64BIT
> - depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
> + depends on TREE_RCU && RCU_EXPERT
> default 64 if 64BIT
> default 32 if !64BIT
> help
> @@ -112,7 +113,7 @@ config RCU_FANOUT_LEAF
> int "Tree-based hierarchical RCU leaf-level fanout value"
> range 2 64 if 64BIT
> range 2 32 if !64BIT
> - depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
> + depends on TREE_RCU && RCU_EXPERT
> default 16
> help
> This option controls the leaf-level fanout of hierarchical
> @@ -187,7 +188,7 @@ config RCU_BOOST_DELAY
>
> config RCU_NOCB_CPU
> bool "Offload RCU callback processing from boot-selected CPUs"
> - depends on TREE_RCU || PREEMPT_RCU
> + depends on TREE_RCU
> depends on RCU_EXPERT || NO_HZ_FULL
> default n
> help
> diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
> index 020e8b6a644b..82d5fba48b2f 100644
> --- a/kernel/rcu/Makefile
> +++ b/kernel/rcu/Makefile
> @@ -9,6 +9,5 @@ obj-$(CONFIG_TINY_SRCU) += srcutiny.o
> obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
> obj-$(CONFIG_RCU_PERF_TEST) += rcuperf.o
> obj-$(CONFIG_TREE_RCU) += tree.o
> -obj-$(CONFIG_PREEMPT_RCU) += tree.o
> obj-$(CONFIG_TINY_RCU) += tiny.o
> obj-$(CONFIG_RCU_NEED_SEGCBLIST) += rcu_segcblist.o
> diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
> index c30a1f7dbd15..a7ab2a023dd3 100644
> --- a/kernel/rcu/rcu.h
> +++ b/kernel/rcu/rcu.h
> @@ -427,7 +427,7 @@ enum rcutorture_type {
> INVALID_RCU_FLAVOR
> };
>
> -#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
> +#if defined(CONFIG_TREE_RCU)
> void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
> unsigned long *gp_seq);
> void do_trace_rcu_torture_read(const char *rcutorturename,
> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> index 196487762b96..2f529470cafa 100644
> --- a/kernel/rcu/update.c
> +++ b/kernel/rcu/update.c
> @@ -437,7 +437,7 @@ struct debug_obj_descr rcuhead_debug_descr = {
> EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
> #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
>
> -#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
> +#if defined(CONFIG_TREE_RCU) || defined(CONFIG_RCU_TRACE)
> void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
> unsigned long secs,
> unsigned long c_old, unsigned long c)
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 00fcea236eba..2ace158a4d72 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1268,7 +1268,7 @@ static struct ctl_table kern_table[] = {
> .proc_handler = proc_do_static_key,
> },
> #endif
> -#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
> +#if defined(CONFIG_TREE_RCU)
> {
> .procname = "panic_on_rcu_stall",
> .data = &sysctl_panic_on_rcu_stall,
> --
> 2.20.1
>
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