Re: [PATCH] rcu: Remove redundant CONFIG_PREEMPT_RCU option

From: Paul E. McKenney
Date: Mon Sep 22 2014 - 13:02:01 EST

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In reply to: Pranith Kumar: "Re: [PATCH] rcu: Remove redundant CONFIG_PREEMPT_RCU option"
Next in thread: Pranith Kumar: "Re: [PATCH] rcu: Remove redundant CONFIG_PREEMPT_RCU option"
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On Mon, Sep 22, 2014 at 12:49:24PM -0400, Pranith Kumar wrote:
> On Mon, Sep 22, 2014 at 12:25 PM, Josh Triplett <josh@xxxxxxxxxxxxxxxx> 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@xxxxxxxxx>
> >
> > 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(-)

Were the bulk of the files defconfig files? These need not be changed,
the architecture maintainers handle them.

Thanx, Paul

> 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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Next message: Milosz Tanski: "Re: [RFC PATCH 0/7] Non-blockling buffered fs read (page cache only)"
Previous message: Joe Perches: "[PATCH] scsi: sas_ata: change ata_<foo>_printk routines to return void"
In reply to: Pranith Kumar: "Re: [PATCH] rcu: Remove redundant CONFIG_PREEMPT_RCU option"
Next in thread: Pranith Kumar: "Re: [PATCH] rcu: Remove redundant CONFIG_PREEMPT_RCU option"
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