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Message-ID: <20191015014650.GL2689@paulmck-ThinkPad-P72>
Date: Mon, 14 Oct 2019 18:46:50 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Joel Fernandes <joel@...lfernandes.org>
Cc: Lai Jiangshan <laijs@...ux.alibaba.com>,
Lai Jiangshan <jiangshanlai@...il.com>,
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>,
Yafang Shao <laoar.shao@...il.com>,
Mike Rapoport <rppt@...ux.ibm.com>,
Petr Mladek <pmladek@...e.com>,
Sakari Ailus <sakari.ailus@...ux.intel.com>,
rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] rcu: make PREEMPT_RCU to be a decoration of TREE_RCU
On Mon, Oct 14, 2019 at 02:48:32PM -0400, Joel Fernandes wrote:
> On Sun, Oct 13, 2019 at 12:59:57PM +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.
> >
>
> Looks like a nice simplification and so far I could not poke any holes in the
> code...
>
> I am in support of this patch for further review and testing. Thanks!
>
> Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
Thank you both!
Lai, what is this patch against? It does not want to apply to the current
-rcu "dev" branch.
Thanx, Paul
> thanks,
>
> - Joel
>
>
> > Signed-off-by: Lai Jiangshan <jiangshanlai@...il.com>
> > Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
> > ---
> > 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 75a2eded7aa2..1eee9f6c27f9 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>
> > @@ -583,7 +583,7 @@ 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 694bd040cf51..1ce15c5be4c8 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
> > @@ -425,7 +425,7 @@ 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 8fd4f82c9b3d..4149ba76824f 100644
> > --- a/kernel/rcu/rcu.h
> > +++ b/kernel/rcu/rcu.h
> > @@ -452,7 +452,7 @@ 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 rcutorture_record_progress(unsigned long vernum);
> > diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
> > index 1861103662db..34a7452b25fd 100644
> > --- a/kernel/rcu/update.c
> > +++ b/kernel/rcu/update.c
> > @@ -435,7 +435,7 @@ 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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