Re: [PATCH -tip] v3 Renamings to increase RCU clarity.
From: Lai Jiangshan
Date: Mon Aug 24 2009 - 03:18:02 EST
Paul E. McKenney wrote:
> From: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
>
> Make RCU-sched, RCU-bh, and RCU-preempt be underlying implementations,
> with "RCU" defined in terms of one of the three. Update the outdated
> rcu_qsctr_inc() names, as these functions no longer increment anything.
>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> ---
> Documentation/RCU/trace.txt | 7 ++--
> include/linux/rcupdate.h | 21 ++++++++---
> include/linux/rcupreempt.h | 4 +-
> include/linux/rcutree.h | 8 +++--
> kernel/rcupreempt.c | 8 ++--
> kernel/rcutree.c | 80 +++++++++++++++++++++++++++----------------
> kernel/rcutree.h | 4 +-
> kernel/rcutree_trace.c | 20 +++++-----
> kernel/sched.c | 2 +-
> kernel/softirq.c | 4 +-
> 10 files changed, 95 insertions(+), 63 deletions(-)
>
> diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt
> index 02cced1..187bbf1 100644
> --- a/Documentation/RCU/trace.txt
> +++ b/Documentation/RCU/trace.txt
> @@ -191,8 +191,7 @@ rcu/rcuhier (which displays the struct rcu_node hierarchy).
>
> The output of "cat rcu/rcudata" looks as follows:
>
> -rcu:
> -rcu:
> +rcu_sched:
> 0 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=10951/1 dn=0 df=1101 of=0 ri=36 ql=0 b=10
> 1 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=16117/1 dn=0 df=1015 of=0 ri=0 ql=0 b=10
> 2 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=1445/1 dn=0 df=1839 of=0 ri=0 ql=0 b=10
> @@ -306,7 +305,7 @@ comma-separated-variable spreadsheet format.
>
> The output of "cat rcu/rcugp" looks as follows:
>
> -rcu: completed=33062 gpnum=33063
> +rcu_sched: completed=33062 gpnum=33063
> rcu_bh: completed=464 gpnum=464
>
> Again, this output is for both "rcu" and "rcu_bh". The fields are
> @@ -413,7 +412,7 @@ o Each element of the form "1/1 0:127 ^0" represents one struct
>
> The output of "cat rcu/rcu_pending" looks as follows:
>
> -rcu:
> +rcu_sched:
> 0 np=255892 qsp=53936 cbr=0 cng=14417 gpc=10033 gps=24320 nf=6445 nn=146741
> 1 np=261224 qsp=54638 cbr=0 cng=25723 gpc=16310 gps=2849 nf=5912 nn=155792
> 2 np=237496 qsp=49664 cbr=0 cng=2762 gpc=45478 gps=1762 nf=1201 nn=136629
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 3c89d6a..e920f0f 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -157,17 +157,28 @@ extern int rcu_scheduler_active;
> * - call_rcu_sched() and rcu_barrier_sched()
> * on the write-side to insure proper synchronization.
> */
> -#define rcu_read_lock_sched() preempt_disable()
> -#define rcu_read_lock_sched_notrace() preempt_disable_notrace()
> +static inline void rcu_read_lock_sched(void)
> +{
> + preempt_disable();
> +}
> +static inline void rcu_read_lock_sched_notrace(void)
> +{
> + preempt_disable_notrace();
> +}
It need be marked "notrace". Sometimes a function marked "inline"
may not be inlined when it is compiled.
Lai.
>
> /*
> * rcu_read_unlock_sched - marks the end of a RCU-classic critical section
> *
> * See rcu_read_lock_sched for more information.
> */
> -#define rcu_read_unlock_sched() preempt_enable()
> -#define rcu_read_unlock_sched_notrace() preempt_enable_notrace()
> -
> +static inline void rcu_read_unlock_sched(void)
> +{
> + preempt_enable();
> +}
> +static inline void rcu_read_unlock_sched_notrace(void)
> +{
> + preempt_enable_notrace();
> +}
>
>
> /**
> diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h
> index f164ac9..2963f08 100644
> --- a/include/linux/rcupreempt.h
> +++ b/include/linux/rcupreempt.h
> @@ -40,8 +40,8 @@
> #include <linux/cpumask.h>
> #include <linux/seqlock.h>
>
> -extern void rcu_qsctr_inc(int cpu);
> -static inline void rcu_bh_qsctr_inc(int cpu) { }
> +extern void rcu_sched_qs(int cpu);
> +static inline void rcu_bh_qs(int cpu) { }
>
> /*
> * Someone might want to pass call_rcu_bh as a function pointer.
> diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
> index e37d5e2..a0852d0 100644
> --- a/include/linux/rcutree.h
> +++ b/include/linux/rcutree.h
> @@ -30,8 +30,8 @@
> #ifndef __LINUX_RCUTREE_H
> #define __LINUX_RCUTREE_H
>
> -extern void rcu_qsctr_inc(int cpu);
> -extern void rcu_bh_qsctr_inc(int cpu);
> +extern void rcu_sched_qs(int cpu);
> +extern void rcu_bh_qs(int cpu);
>
> extern int rcu_pending(int cpu);
> extern int rcu_needs_cpu(int cpu);
> @@ -73,7 +73,8 @@ static inline void __rcu_read_unlock_bh(void)
>
> #define __synchronize_sched() synchronize_rcu()
>
> -#define call_rcu_sched(head, func) call_rcu(head, func)
> +extern void call_rcu_sched(struct rcu_head *head,
> + void (*func)(struct rcu_head *rcu));
>
> static inline void synchronize_rcu_expedited(void)
> {
> @@ -91,6 +92,7 @@ extern void rcu_restart_cpu(int cpu);
>
> extern long rcu_batches_completed(void);
> extern long rcu_batches_completed_bh(void);
> +extern long rcu_batches_completed_sched(void);
>
> static inline void rcu_init_sched(void)
> {
> diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c
> index 510898a..0eef9b7 100644
> --- a/kernel/rcupreempt.c
> +++ b/kernel/rcupreempt.c
> @@ -159,7 +159,7 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_dyntick_sched, rcu_dyntick_sched
> .dynticks = 1,
> };
>
> -void rcu_qsctr_inc(int cpu)
> +void rcu_sched_qs(int cpu)
> {
> struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu);
>
> @@ -967,12 +967,12 @@ void rcu_check_callbacks(int cpu, int user)
> * If this CPU took its interrupt from user mode or from the
> * idle loop, and this is not a nested interrupt, then
> * this CPU has to have exited all prior preept-disable
> - * sections of code. So increment the counter to note this.
> + * sections of code. So invoke rcu_sched_qs() to note this.
> *
> * The memory barrier is needed to handle the case where
> * writes from a preempt-disable section of code get reordered
> * into schedule() by this CPU's write buffer. So the memory
> - * barrier makes sure that the rcu_qsctr_inc() is seen by other
> + * barrier makes sure that the rcu_sched_qs() is seen by other
> * CPUs to happen after any such write.
> */
>
> @@ -980,7 +980,7 @@ void rcu_check_callbacks(int cpu, int user)
> (idle_cpu(cpu) && !in_softirq() &&
> hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
> smp_mb(); /* Guard against aggressive schedule(). */
> - rcu_qsctr_inc(cpu);
> + rcu_sched_qs(cpu);
> }
>
> rcu_check_mb(cpu);
> diff --git a/kernel/rcutree.c b/kernel/rcutree.c
> index a162f85..4d71d4e 100644
> --- a/kernel/rcutree.c
> +++ b/kernel/rcutree.c
> @@ -74,26 +74,25 @@ EXPORT_SYMBOL_GPL(rcu_lock_map);
> .n_force_qs_ngp = 0, \
> }
>
> -struct rcu_state rcu_state = RCU_STATE_INITIALIZER(rcu_state);
> -DEFINE_PER_CPU(struct rcu_data, rcu_data);
> +struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state);
> +DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
>
> struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state);
> DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
>
> /*
> - * Increment the quiescent state counter.
> - * The counter is a bit degenerated: We do not need to know
> + * Note a quiescent state. Because we do not need to know
> * how many quiescent states passed, just if there was at least
> - * one since the start of the grace period. Thus just a flag.
> + * one since the start of the grace period, this just sets a flag.
> */
> -void rcu_qsctr_inc(int cpu)
> +void rcu_sched_qs(int cpu)
> {
> - struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
> + struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
> rdp->passed_quiesc = 1;
> rdp->passed_quiesc_completed = rdp->completed;
> }
>
> -void rcu_bh_qsctr_inc(int cpu)
> +void rcu_bh_qs(int cpu)
> {
> struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
> rdp->passed_quiesc = 1;
> @@ -114,11 +113,21 @@ static int qlowmark = 100; /* Once only this many pending, use blimit. */
> static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
>
> /*
> + * Return the number of RCU-sched batches processed thus far for debug & stats.
> + */
> +long rcu_batches_completed_sched(void)
> +{
> + return rcu_sched_state.completed;
> +}
> +EXPORT_SYMBOL_GPL(rcu_batches_completed_sched);
> +
> +/*
> * Return the number of RCU batches processed thus far for debug & stats.
> + * @@@ placeholder, maps to rcu_batches_completed_sched().
> */
> long rcu_batches_completed(void)
> {
> - return rcu_state.completed;
> + return rcu_batches_completed_sched();
> }
> EXPORT_SYMBOL_GPL(rcu_batches_completed);
>
> @@ -310,7 +319,7 @@ void rcu_irq_exit(void)
> WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs);
>
> /* If the interrupt queued a callback, get out of dyntick mode. */
> - if (__get_cpu_var(rcu_data).nxtlist ||
> + if (__get_cpu_var(rcu_sched_data).nxtlist ||
> __get_cpu_var(rcu_bh_data).nxtlist)
> set_need_resched();
> }
> @@ -847,7 +856,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
> /*
> * Move callbacks from the outgoing CPU to the running CPU.
> * Note that the outgoing CPU is now quiscent, so it is now
> - * (uncharacteristically) safe to access it rcu_data structure.
> + * (uncharacteristically) safe to access its rcu_data structure.
> * Note also that we must carefully retain the order of the
> * outgoing CPU's callbacks in order for rcu_barrier() to work
> * correctly. Finally, note that we start all the callbacks
> @@ -878,7 +887,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
> */
> static void rcu_offline_cpu(int cpu)
> {
> - __rcu_offline_cpu(cpu, &rcu_state);
> + __rcu_offline_cpu(cpu, &rcu_sched_state);
> __rcu_offline_cpu(cpu, &rcu_bh_state);
> }
>
> @@ -973,17 +982,16 @@ void rcu_check_callbacks(int cpu, int user)
> * Get here if this CPU took its interrupt from user
> * mode or from the idle loop, and if this is not a
> * nested interrupt. In this case, the CPU is in
> - * a quiescent state, so count it.
> + * a quiescent state, so note it.
> *
> * No memory barrier is required here because both
> - * rcu_qsctr_inc() and rcu_bh_qsctr_inc() reference
> - * only CPU-local variables that other CPUs neither
> - * access nor modify, at least not while the corresponding
> - * CPU is online.
> + * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local
> + * variables that other CPUs neither access nor modify,
> + * at least not while the corresponding CPU is online.
> */
>
> - rcu_qsctr_inc(cpu);
> - rcu_bh_qsctr_inc(cpu);
> + rcu_sched_qs(cpu);
> + rcu_bh_qs(cpu);
>
> } else if (!in_softirq()) {
>
> @@ -991,10 +999,10 @@ void rcu_check_callbacks(int cpu, int user)
> * Get here if this CPU did not take its interrupt from
> * softirq, in other words, if it is not interrupting
> * a rcu_bh read-side critical section. This is an _bh
> - * critical section, so count it.
> + * critical section, so note it.
> */
>
> - rcu_bh_qsctr_inc(cpu);
> + rcu_bh_qs(cpu);
> }
> raise_softirq(RCU_SOFTIRQ);
> }
> @@ -1174,7 +1182,8 @@ static void rcu_process_callbacks(struct softirq_action *unused)
> */
> smp_mb(); /* See above block comment. */
>
> - __rcu_process_callbacks(&rcu_state, &__get_cpu_var(rcu_data));
> + __rcu_process_callbacks(&rcu_sched_state,
> + &__get_cpu_var(rcu_sched_data));
> __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
>
> /*
> @@ -1231,14 +1240,25 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
> }
>
> /*
> - * Queue an RCU callback for invocation after a grace period.
> + * Queue an RCU-sched callback for invocation after a grace period.
> + */
> +void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
> +{
> + __call_rcu(head, func, &rcu_sched_state);
> +}
> +EXPORT_SYMBOL_GPL(call_rcu_sched);
> +
> +/*
> + * @@@ Queue an RCU callback for invocation after a grace period.
> + * @@@ Placeholder pending rcutree_plugin.h.
> */
> void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
> {
> - __call_rcu(head, func, &rcu_state);
> + call_rcu_sched(head, func);
> }
> EXPORT_SYMBOL_GPL(call_rcu);
>
> +
> /*
> * Queue an RCU for invocation after a quicker grace period.
> */
> @@ -1311,7 +1331,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
> */
> int rcu_pending(int cpu)
> {
> - return __rcu_pending(&rcu_state, &per_cpu(rcu_data, cpu)) ||
> + return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) ||
> __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu));
> }
>
> @@ -1324,7 +1344,7 @@ int rcu_pending(int cpu)
> int rcu_needs_cpu(int cpu)
> {
> /* RCU callbacks either ready or pending? */
> - return per_cpu(rcu_data, cpu).nxtlist ||
> + return per_cpu(rcu_sched_data, cpu).nxtlist ||
> per_cpu(rcu_bh_data, cpu).nxtlist;
> }
>
> @@ -1418,7 +1438,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
>
> static void __cpuinit rcu_online_cpu(int cpu)
> {
> - rcu_init_percpu_data(cpu, &rcu_state);
> + rcu_init_percpu_data(cpu, &rcu_sched_state);
> rcu_init_percpu_data(cpu, &rcu_bh_state);
> }
>
> @@ -1545,10 +1565,10 @@ void __init __rcu_init(void)
> #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
> printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n");
> #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
> - rcu_init_one(&rcu_state);
> - RCU_DATA_PTR_INIT(&rcu_state, rcu_data);
> + rcu_init_one(&rcu_sched_state);
> + RCU_DATA_PTR_INIT(&rcu_sched_state, rcu_sched_data);
> for_each_possible_cpu(i)
> - rcu_boot_init_percpu_data(i, &rcu_state);
> + rcu_boot_init_percpu_data(i, &rcu_sched_state);
> rcu_init_one(&rcu_bh_state);
> RCU_DATA_PTR_INIT(&rcu_bh_state, rcu_bh_data);
> for_each_possible_cpu(i)
> diff --git a/kernel/rcutree.h b/kernel/rcutree.h
> index 7cc830a..0024e5d 100644
> --- a/kernel/rcutree.h
> +++ b/kernel/rcutree.h
> @@ -238,8 +238,8 @@ struct rcu_state {
> /*
> * RCU implementation internal declarations:
> */
> -extern struct rcu_state rcu_state;
> -DECLARE_PER_CPU(struct rcu_data, rcu_data);
> +extern struct rcu_state rcu_sched_state;
> +DECLARE_PER_CPU(struct rcu_data, rcu_sched_data);
>
> extern struct rcu_state rcu_bh_state;
> DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
> diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
> index 0cb52b8..236c050 100644
> --- a/kernel/rcutree_trace.c
> +++ b/kernel/rcutree_trace.c
> @@ -77,8 +77,8 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
>
> static int show_rcudata(struct seq_file *m, void *unused)
> {
> - seq_puts(m, "rcu:\n");
> - PRINT_RCU_DATA(rcu_data, print_one_rcu_data, m);
> + seq_puts(m, "rcu_sched:\n");
> + PRINT_RCU_DATA(rcu_sched_data, print_one_rcu_data, m);
> seq_puts(m, "rcu_bh:\n");
> PRINT_RCU_DATA(rcu_bh_data, print_one_rcu_data, m);
> return 0;
> @@ -125,8 +125,8 @@ static int show_rcudata_csv(struct seq_file *m, void *unused)
> seq_puts(m, "\"dt\",\"dt nesting\",\"dn\",\"df\",");
> #endif /* #ifdef CONFIG_NO_HZ */
> seq_puts(m, "\"of\",\"ri\",\"ql\",\"b\"\n");
> - seq_puts(m, "\"rcu:\"\n");
> - PRINT_RCU_DATA(rcu_data, print_one_rcu_data_csv, m);
> + seq_puts(m, "\"rcu_sched:\"\n");
> + PRINT_RCU_DATA(rcu_sched_data, print_one_rcu_data_csv, m);
> seq_puts(m, "\"rcu_bh:\"\n");
> PRINT_RCU_DATA(rcu_bh_data, print_one_rcu_data_csv, m);
> return 0;
> @@ -172,8 +172,8 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
>
> static int show_rcuhier(struct seq_file *m, void *unused)
> {
> - seq_puts(m, "rcu:\n");
> - print_one_rcu_state(m, &rcu_state);
> + seq_puts(m, "rcu_sched:\n");
> + print_one_rcu_state(m, &rcu_sched_state);
> seq_puts(m, "rcu_bh:\n");
> print_one_rcu_state(m, &rcu_bh_state);
> return 0;
> @@ -194,8 +194,8 @@ static struct file_operations rcuhier_fops = {
>
> static int show_rcugp(struct seq_file *m, void *unused)
> {
> - seq_printf(m, "rcu: completed=%ld gpnum=%ld\n",
> - rcu_state.completed, rcu_state.gpnum);
> + seq_printf(m, "rcu_sched: completed=%ld gpnum=%ld\n",
> + rcu_sched_state.completed, rcu_sched_state.gpnum);
> seq_printf(m, "rcu_bh: completed=%ld gpnum=%ld\n",
> rcu_bh_state.completed, rcu_bh_state.gpnum);
> return 0;
> @@ -244,8 +244,8 @@ static void print_rcu_pendings(struct seq_file *m, struct rcu_state *rsp)
>
> static int show_rcu_pending(struct seq_file *m, void *unused)
> {
> - seq_puts(m, "rcu:\n");
> - print_rcu_pendings(m, &rcu_state);
> + seq_puts(m, "rcu_sched:\n");
> + print_rcu_pendings(m, &rcu_sched_state);
> seq_puts(m, "rcu_bh:\n");
> print_rcu_pendings(m, &rcu_bh_state);
> return 0;
> diff --git a/kernel/sched.c b/kernel/sched.c
> index cda8b81..c9beca6 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -5325,7 +5325,7 @@ need_resched:
> preempt_disable();
> cpu = smp_processor_id();
> rq = cpu_rq(cpu);
> - rcu_qsctr_inc(cpu);
> + rcu_sched_qs(cpu);
> prev = rq->curr;
> switch_count = &prev->nivcsw;
>
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index eb5e131..7db2506 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -227,7 +227,7 @@ restart:
> preempt_count() = prev_count;
> }
>
> - rcu_bh_qsctr_inc(cpu);
> + rcu_bh_qs(cpu);
> }
> h++;
> pending >>= 1;
> @@ -721,7 +721,7 @@ static int ksoftirqd(void * __bind_cpu)
> preempt_enable_no_resched();
> cond_resched();
> preempt_disable();
> - rcu_qsctr_inc((long)__bind_cpu);
> + rcu_sched_qs((long)__bind_cpu);
> }
> preempt_enable();
> set_current_state(TASK_INTERRUPTIBLE);
--
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