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    SubjectRe: [PATCH -tip] v3 Renamings to increase RCU clarity.
    Paul E. McKenney wrote:
    > From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    >
    > 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 Update the outdated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@linux.vnet.ibm.com>
    > ---
    > 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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