rcu: Rename rcu_check_callbacks() to rcu_sched_clock_irq()

The name rcu_check_callbacks() arguably made sense back in the early
2000s when RCU was quite a bit simpler than it is today, but it has
become quite misleading, especially with the advent of dyntick-idle
and NO_HZ_FULL.  The rcu_check_callbacks() function is RCU's hook into
the scheduling-clock interrupt, and is now but one of many ways that
callbacks get promoted to invocable state.

This commit therefore changes the name to rcu_sched_clock_irq(),
which is the same number of characters and clearly indicates this
function's relation to the rest of the Linux kernel.  In addition, for
the sake of consistency, rcu_flavor_check_callbacks() is also renamed
to rcu_flavor_sched_clock_irq().

While in the area, the header comments for both functions are reworked.

Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-11-21 11:35:03 -08:00
parent 2aa5503026
commit c98cac603f
10 changed files with 29 additions and 33 deletions

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@ -485,7 +485,7 @@ section that the grace period must wait on.
noted by <tt>rcu_node_context_switch()</tt> on the left.
On the other hand, if the CPU takes a scheduler-clock interrupt
while executing in usermode, a quiescent state will be noted by
<tt>rcu_check_callbacks()</tt> on the right.
<tt>rcu_sched_clock_irq()</tt> on the right.
Either way, the passage through a quiescent state will be noted
in a per-CPU variable.
@ -651,7 +651,7 @@ to end.
These callbacks are identified by <tt>rcu_advance_cbs()</tt>,
which is usually invoked by <tt>__note_gp_changes()</tt>.
As shown in the diagram below, this invocation can be triggered by
the scheduling-clock interrupt (<tt>rcu_check_callbacks()</tt> on
the scheduling-clock interrupt (<tt>rcu_sched_clock_irq()</tt> on
the left) or by idle entry (<tt>rcu_cleanup_after_idle()</tt> on
the right, but only for kernels build with
<tt>CONFIG_RCU_FAST_NO_HZ=y</tt>).

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@ -349,7 +349,7 @@
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id="text202-7-5"
style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcu_check_callbacks()</text>
style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcu_sched_clock_irq()</text>
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@ -3902,7 +3902,7 @@
font-style="normal"
y="-4418.6582"
x="3745.7725"
xml:space="preserve">rcu_check_callbacks()</text>
xml:space="preserve">rcu_sched_clock_irq()</text>
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@ -4968,7 +4968,7 @@
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style="font-size:192px;font-style:normal;font-weight:bold;text-anchor:start;fill:#000000;stroke-width:0.025in;font-family:Courier">rcu_check_callbacks()</text>
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@ -775,7 +775,7 @@
font-style="normal"
y="-4418.6582"
x="3745.7725"
xml:space="preserve">rcu_check_callbacks()</text>
xml:space="preserve">rcu_sched_clock_irq()</text>
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@ -89,7 +89,7 @@ static inline int rcu_preempt_depth(void)
/* Internal to kernel */
void rcu_init(void);
extern int rcu_scheduler_active __read_mostly;
void rcu_check_callbacks(int user);
void rcu_sched_clock_irq(int user);
void rcu_report_dead(unsigned int cpu);
void rcutree_migrate_callbacks(int cpu);

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@ -76,7 +76,7 @@ void rcu_qs(void)
* be called from hardirq context. It is normally called from the
* scheduling-clock interrupt.
*/
void rcu_check_callbacks(int user)
void rcu_sched_clock_irq(int user)
{
if (user) {
rcu_qs();

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@ -1139,7 +1139,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
}
/*
* NO_HZ_FULL CPUs can run in-kernel without rcu_check_callbacks!
* NO_HZ_FULL CPUs can run in-kernel without rcu_sched_clock_irq!
* The above code handles this, but only for straight cond_resched().
* And some in-kernel loops check need_resched() before calling
* cond_resched(), which defeats the above code for CPUs that are
@ -2532,14 +2532,14 @@ static void rcu_do_batch(struct rcu_data *rdp)
}
/*
* Check to see if this CPU is in a non-context-switch quiescent state
* (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
* Also schedule RCU core processing.
*
* This function must be called from hardirq context. It is normally
* invoked from the scheduling-clock interrupt.
* This function is invoked from each scheduling-clock interrupt,
* and checks to see if this CPU is in a non-context-switch quiescent
* state, for example, user mode or idle loop. It also schedules RCU
* core processing. If the current grace period has gone on too long,
* it will ask the scheduler to manufacture a context switch for the sole
* purpose of providing a providing the needed quiescent state.
*/
void rcu_check_callbacks(int user)
void rcu_sched_clock_irq(int user)
{
trace_rcu_utilization(TPS("Start scheduler-tick"));
raw_cpu_inc(rcu_data.ticks_this_gp);
@ -2552,7 +2552,7 @@ void rcu_check_callbacks(int user)
}
__this_cpu_write(rcu_data.rcu_urgent_qs, false);
}
rcu_flavor_check_callbacks(user);
rcu_flavor_sched_clock_irq(user);
if (rcu_pending())
invoke_rcu_core();

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@ -417,7 +417,7 @@ static void rcu_print_detail_task_stall(void);
static int rcu_print_task_stall(struct rcu_node *rnp);
static int rcu_print_task_exp_stall(struct rcu_node *rnp);
static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp);
static void rcu_flavor_check_callbacks(int user);
static void rcu_flavor_sched_clock_irq(int user);
void call_rcu(struct rcu_head *head, rcu_callback_t func);
static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);

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@ -297,7 +297,7 @@ static void rcu_qs(void)
__this_cpu_read(rcu_data.gp_seq),
TPS("cpuqs"));
__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
barrier(); /* Coordinate with rcu_flavor_check_callbacks(). */
barrier(); /* Coordinate with rcu_flavor_sched_clock_irq(). */
current->rcu_read_unlock_special.b.need_qs = false;
}
}
@ -778,13 +778,13 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
}
/*
* Check for a quiescent state from the current CPU. When a task blocks,
* the task is recorded in the corresponding CPU's rcu_node structure,
* which is checked elsewhere.
*
* Caller must disable hard irqs.
* Check for a quiescent state from the current CPU, including voluntary
* context switches for Tasks RCU. When a task blocks, the task is
* recorded in the corresponding CPU's rcu_node structure, which is checked
* elsewhere, hence this function need only check for quiescent states
* related to the current CPU, not to those related to tasks.
*/
static void rcu_flavor_check_callbacks(int user)
static void rcu_flavor_sched_clock_irq(int user)
{
struct task_struct *t = current;
@ -1030,14 +1030,10 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
}
/*
* Check to see if this CPU is in a non-context-switch quiescent state
* (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
* Also schedule RCU core processing.
*
* This function must be called from hardirq context. It is normally
* invoked from the scheduling-clock interrupt.
* Check to see if this CPU is in a non-context-switch quiescent state,
* namely user mode and idle loop.
*/
static void rcu_flavor_check_callbacks(int user)
static void rcu_flavor_sched_clock_irq(int user)
{
if (user || rcu_is_cpu_rrupt_from_idle()) {

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@ -1632,7 +1632,7 @@ void update_process_times(int user_tick)
/* Note: this timer irq context must be accounted for as well. */
account_process_tick(p, user_tick);
run_local_timers();
rcu_check_callbacks(user_tick);
rcu_sched_clock_irq(user_tick);
#ifdef CONFIG_IRQ_WORK
if (in_irq())
irq_work_tick();