Messages in this thread | | | Date | Mon, 22 Sep 2014 09:44:58 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] rcu: Remove redundant CONFIG_PREEMPT_RCU option |
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On Mon, Sep 22, 2014 at 09:25:34AM -0700, Josh Triplett 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@gmail.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.
Given that there has thus far been no fewer than three distinct implementations of PREEMPT_RCU (one in -rt, the first in mainline, and the current one in mainline), it would indeed be quite wise to avoid assuming that there never will be some new PREEMPT_RCU implementation. ;-)
Thanx, Paul
> - Josh Triplett > > > arch/xtensa/configs/s6105_defconfig | 2 +- > > include/linux/init_task.h | 2 +- > > include/linux/rcupdate.h | 16 ++++++++-------- > > include/linux/sched.h | 10 +++++----- > > init/Kconfig | 6 ------ > > kernel/rcu/update.c | 4 ++-- > > tools/testing/selftests/rcutorture/doc/TINY_RCU.txt | 2 +- > > .../selftests/rcutorture/doc/TREE_RCU-kconfig.txt | 2 +- > > 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 > > >
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