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Message-ID: <CAJhHMCCpkVqdbMirw2ON=4+pPQgWKczgq_Y9BCv3_fj6yGp_MQ@mail.gmail.com>
Date: Mon, 22 Sep 2014 12:49:24 -0400
From: Pranith Kumar <bobby.prani@...il.com>
To: Josh Triplett <josh@...htriplett.org>
Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Steven Rostedt <rostedt@...dmis.org>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Lai Jiangshan <laijs@...fujitsu.com>,
open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] rcu: Remove redundant CONFIG_PREEMPT_RCU option
On Mon, Sep 22, 2014 at 12:25 PM, Josh Triplett <josh@...htriplett.org> wrote:
> On Sun, Sep 21, 2014 at 12:49:54PM -0400, Pranith Kumar wrote:
>> PREEMPT_RCU and TREE_PREEMPT_RCU serve the same function after TINY_PREEMPT_RCU
>> has been removed. This patch removes CONFIG_PREEMPT_RCU and uses
>> CONFIG_TREE_PREEMPT_RCU in its place.
>>
>> Signed-off-by: Pranith Kumar <bobby.prani@...il.com>
>
> I think it would actually make more sense to do this the other way
> around, if at all: drop TREE_PREEMPT_RCU in favor of PREEMPT_RCU. The
> instances shown here don't care about *which* preemptible RCU
> implementation the kernel uses, they just need to behave differently
> when preemptible. Let's also not assume that no new RCU implementation
> will ever arise superceding TREE_PREEMPT_RCU.
That is exactly what I did first and got the following changelog:
51 files changed, 77 insertions(+), 83 deletions(-)
compared to
8 files changed, 19 insertions(+), 25 deletions(-)
for the current one. Hence my patch opting for the latter. I will go
ahead and send the other patch.
>> 8 files changed, 19 insertions(+), 25 deletions(-)
>>
>> diff --git a/arch/xtensa/configs/s6105_defconfig b/arch/xtensa/configs/s6105_defconfig
>> index 12a492a..dab1a99 100644
>> --- a/arch/xtensa/configs/s6105_defconfig
>> +++ b/arch/xtensa/configs/s6105_defconfig
>> @@ -35,7 +35,7 @@ CONFIG_SYSVIPC_SYSCTL=y
>> #
>> # CONFIG_CLASSIC_RCU is not set
>> # CONFIG_TREE_RCU is not set
>> -CONFIG_PREEMPT_RCU=y
>> +CONFIG_TREE_PREEMPT_RCU=y
>> # CONFIG_RCU_TRACE is not set
>> # CONFIG_TREE_RCU_TRACE is not set
>> # CONFIG_PREEMPT_RCU_TRACE is not set
>> diff --git a/include/linux/init_task.h b/include/linux/init_task.h
>> index 77fc43f..39600f4 100644
>> --- a/include/linux/init_task.h
>> +++ b/include/linux/init_task.h
>> @@ -108,7 +108,7 @@ extern struct group_info init_groups;
>> #else
>> #define INIT_TASK_RCU_TREE_PREEMPT(tsk)
>> #endif
>> -#ifdef CONFIG_PREEMPT_RCU
>> +#ifdef CONFIG_TREE_PREEMPT_RCU
>> #define INIT_TASK_RCU_PREEMPT(tsk) \
>> .rcu_read_lock_nesting = 0, \
>> .rcu_read_unlock_special.s = 0, \
>> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
>> index a4a819f..17a15d5 100644
>> --- a/include/linux/rcupdate.h
>> +++ b/include/linux/rcupdate.h
>> @@ -103,7 +103,7 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
>>
>> /* Exported common interfaces */
>>
>> -#ifdef CONFIG_PREEMPT_RCU
>> +#ifdef CONFIG_TREE_PREEMPT_RCU
>>
>> /**
>> * call_rcu() - Queue an RCU callback for invocation after a grace period.
>> @@ -140,12 +140,12 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
>> void call_rcu(struct rcu_head *head,
>> void (*func)(struct rcu_head *head));
>>
>> -#else /* #ifdef CONFIG_PREEMPT_RCU */
>> +#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
>>
>> /* In classic RCU, call_rcu() is just call_rcu_sched(). */
>> #define call_rcu call_rcu_sched
>>
>> -#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
>> +#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
>>
>> /**
>> * call_rcu_bh() - Queue an RCU for invocation after a quicker grace period.
>> @@ -217,7 +217,7 @@ void call_rcu_tasks(struct rcu_head *head, void (*func)(struct rcu_head *head));
>> void synchronize_rcu_tasks(void);
>> void rcu_barrier_tasks(void);
>>
>> -#ifdef CONFIG_PREEMPT_RCU
>> +#ifdef CONFIG_TREE_PREEMPT_RCU
>>
>> void __rcu_read_lock(void);
>> void __rcu_read_unlock(void);
>> @@ -227,12 +227,12 @@ void synchronize_rcu(void);
>> /*
>> * Defined as a macro as it is a very low level header included from
>> * areas that don't even know about current. This gives the rcu_read_lock()
>> - * nesting depth, but makes sense only if CONFIG_PREEMPT_RCU -- in other
>> + * nesting depth, but makes sense only if CONFIG_TREE_PREEMPT_RCU -- in other
>> * types of kernel builds, the rcu_read_lock() nesting depth is unknowable.
>> */
>> #define rcu_preempt_depth() (current->rcu_read_lock_nesting)
>>
>> -#else /* #ifdef CONFIG_PREEMPT_RCU */
>> +#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */
>>
>> static inline void __rcu_read_lock(void)
>> {
>> @@ -254,7 +254,7 @@ static inline int rcu_preempt_depth(void)
>> return 0;
>> }
>>
>> -#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
>> +#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */
>>
>> /* Internal to kernel */
>> void rcu_init(void);
>> @@ -530,7 +530,7 @@ static inline int rcu_read_lock_sched_held(void)
>> } \
>> } while (0)
>>
>> -#if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_PREEMPT_RCU)
>> +#if defined(CONFIG_PROVE_RCU) && !defined(CONFIG_TREE_PREEMPT_RCU)
>> static inline void rcu_preempt_sleep_check(void)
>> {
>> rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>> index 42888d7..6acaa30 100644
>> --- a/include/linux/sched.h
>> +++ b/include/linux/sched.h
>> @@ -1269,11 +1269,11 @@ struct task_struct {
>> int nr_cpus_allowed;
>> cpumask_t cpus_allowed;
>>
>> -#ifdef CONFIG_PREEMPT_RCU
>> +#ifdef CONFIG_TREE_PREEMPT_RCU
>> int rcu_read_lock_nesting;
>> union rcu_special rcu_read_unlock_special;
>> struct list_head rcu_node_entry;
>> -#endif /* #ifdef CONFIG_PREEMPT_RCU */
>> +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
>> #ifdef CONFIG_TREE_PREEMPT_RCU
>> struct rcu_node *rcu_blocked_node;
>> #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
>> @@ -2014,12 +2014,12 @@ extern void task_clear_jobctl_pending(struct task_struct *task,
>>
>> static inline void rcu_copy_process(struct task_struct *p)
>> {
>> -#ifdef CONFIG_PREEMPT_RCU
>> +#ifdef CONFIG_TREE_PREEMPT_RCU
>> p->rcu_read_lock_nesting = 0;
>> p->rcu_read_unlock_special.s = 0;
>> p->rcu_blocked_node = NULL;
>> INIT_LIST_HEAD(&p->rcu_node_entry);
>> -#endif /* #ifdef CONFIG_PREEMPT_RCU */
>> +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
>> #ifdef CONFIG_TASKS_RCU
>> p->rcu_tasks_holdout = false;
>> INIT_LIST_HEAD(&p->rcu_tasks_holdout_list);
>> @@ -2752,7 +2752,7 @@ extern int __cond_resched_softirq(void);
>>
>> static inline void cond_resched_rcu(void)
>> {
>> -#if defined(CONFIG_DEBUG_ATOMIC_SLEEP) || !defined(CONFIG_PREEMPT_RCU)
>> +#if defined(CONFIG_DEBUG_ATOMIC_SLEEP) || !defined(CONFIG_TREE_PREEMPT_RCU)
>> rcu_read_unlock();
>> cond_resched();
>> rcu_read_lock();
>> diff --git a/init/Kconfig b/init/Kconfig
>> index 8a2b97c..27ad03c 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -501,12 +501,6 @@ config TINY_RCU
>>
>> endchoice
>>
>> -config PREEMPT_RCU
>> - def_bool TREE_PREEMPT_RCU
>> - help
>> - This option enables preemptible-RCU code that is common between
>> - TREE_PREEMPT_RCU and, in the old days, TINY_PREEMPT_RCU.
>> -
>> config TASKS_RCU
>> bool "Task_based RCU implementation using voluntary context switch"
>> default n
>> diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
>> index 3ef8ba5..8848a32 100644
>> --- a/kernel/rcu/update.c
>> +++ b/kernel/rcu/update.c
>> @@ -62,7 +62,7 @@ MODULE_ALIAS("rcupdate");
>>
>> module_param(rcu_expedited, int, 0);
>>
>> -#ifdef CONFIG_PREEMPT_RCU
>> +#ifdef CONFIG_TREE_PREEMPT_RCU
>>
>> /*
>> * Preemptible RCU implementation for rcu_read_lock().
>> @@ -108,7 +108,7 @@ void __rcu_read_unlock(void)
>> }
>> EXPORT_SYMBOL_GPL(__rcu_read_unlock);
>>
>> -#endif /* #ifdef CONFIG_PREEMPT_RCU */
>> +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
>>
>> #ifdef CONFIG_DEBUG_LOCK_ALLOC
>> static struct lock_class_key rcu_lock_key;
>> diff --git a/tools/testing/selftests/rcutorture/doc/TINY_RCU.txt b/tools/testing/selftests/rcutorture/doc/TINY_RCU.txt
>> index 28db67b..4fea92d 100644
>> --- a/tools/testing/selftests/rcutorture/doc/TINY_RCU.txt
>> +++ b/tools/testing/selftests/rcutorture/doc/TINY_RCU.txt
>> @@ -31,7 +31,7 @@ CONFIG_RCU_TORTURE_TEST
>>
>> CONFIG_HOTPLUG_CPU
>> CONFIG_PREEMPT
>> -CONFIG_PREEMPT_RCU
>> +CONFIG_TREE_PREEMPT_RCU
>> CONFIG_SMP
>> CONFIG_TINY_RCU
>> CONFIG_TREE_PREEMPT_RCU
>> diff --git a/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
>> index f85c45e..081dece 100644
>> --- a/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
>> +++ b/tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt
>> @@ -62,7 +62,7 @@ CONFIG_NO_HZ_FULL_SYSIDLE_SMALL
>> Defer until Frederic uses this.
>>
>> CONFIG_PREEMPT_COUNT
>> -CONFIG_PREEMPT_RCU
>> +CONFIG_TREE_PREEMPT_RCU
>>
>> Redundant with CONFIG_PREEMPT, ignore.
>>
>> --
>> 2.1.0
>>
--
Pranith
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