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Message-ID: <ad88e699-5eba-e425-77ae-a73bcf4492e0@linux.alibaba.com>
Date: Tue, 15 Oct 2019 11:01:00 +0800
From: Lai Jiangshan <laijs@...ux.alibaba.com>
To: paulmck@...nel.org, Lai Jiangshan <jiangshanlai@...il.com>
Cc: 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>,
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, LKML <linux-kernel@...r.kernel.org>,
Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] rcu: make PREEMPT_RCU to be a decoration of TREE_RCU
On 2019/10/15 10:45 上午, Lai Jiangshan wrote:
>
>
> On 2019/10/15 10:00 上午, Paul E. McKenney wrote:
>> On Tue, Oct 15, 2019 at 09:50:21AM +0800, Lai Jiangshan wrote:
>>> On Tue, Oct 15, 2019 at 9:46 AM Paul E. McKenney <paulmck@...nel.org>
>>> wrote:
>>>>
>>>> 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.
>>>
>>> Oh, sorry
>>>
>>> I wrongly made the change base on upstream.
>>> I will rebase later.
>>
>> Very good, looking forward to this updated version.
>>
>> Thanx, Paul
>
>
> In my box, the patch can be applied to the -rcu "dev" well.
Oh, I first applied it by "git cherry-pick" not "git am".
It did have conflicts when using "git am". Updated patch
was sent, sorry for the nosing.
thanks
Lai
> And there is nothing strange after boot.
>
> Have I just made a mistake a again? In my box, the HEAD
> of -rcu "dev" is 9725023b ("torture: Handle jitter for CPUs that cannot
> be offlined")
>
> Thanks
> Lai
>
>>
>>> thanks
>>> Lai
>>>
>>>>
>>>> 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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