kernel-ark/kernel/rcutiny.c
Paul E. McKenney 4968c300e1 rcu: Augment rcu_batch_end tracing for idle and callback state
The current rcu_batch_end event trace records only the name of the RCU
flavor and the total number of callbacks that remain queued on the
current CPU.  This is insufficient for testing and tuning the new
dyntick-idle RCU_FAST_NO_HZ code, so this commit adds idle state along
with whether or not any of the callbacks that were ready to invoke
at the beginning of rcu_do_batch() are still queued.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2011-12-11 10:32:22 -08:00

366 lines
9.6 KiB
C

/*
* Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Copyright IBM Corporation, 2008
*
* Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*
* For detailed explanation of Read-Copy Update mechanism see -
* Documentation/RCU
*/
#include <linux/completion.h>
#include <linux/interrupt.h>
#include <linux/notifier.h>
#include <linux/rcupdate.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/cpu.h>
#include <linux/prefetch.h>
#ifdef CONFIG_RCU_TRACE
#include <trace/events/rcu.h>
#endif /* #else #ifdef CONFIG_RCU_TRACE */
#include "rcu.h"
/* Forward declarations for rcutiny_plugin.h. */
struct rcu_ctrlblk;
static void invoke_rcu_callbacks(void);
static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp);
static void rcu_process_callbacks(struct softirq_action *unused);
static void __call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *rcu),
struct rcu_ctrlblk *rcp);
#include "rcutiny_plugin.h"
static long long rcu_dynticks_nesting = DYNTICK_TASK_NESTING;
/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
static void rcu_idle_enter_common(long long oldval)
{
if (rcu_dynticks_nesting) {
RCU_TRACE(trace_rcu_dyntick("--=",
oldval, rcu_dynticks_nesting));
return;
}
RCU_TRACE(trace_rcu_dyntick("Start", oldval, rcu_dynticks_nesting));
if (!is_idle_task(current)) {
struct task_struct *idle = idle_task(smp_processor_id());
RCU_TRACE(trace_rcu_dyntick("Error on entry: not idle task",
oldval, rcu_dynticks_nesting));
ftrace_dump(DUMP_ALL);
WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
}
rcu_sched_qs(0); /* implies rcu_bh_qsctr_inc(0) */
}
/*
* Enter idle, which is an extended quiescent state if we have fully
* entered that mode (i.e., if the new value of dynticks_nesting is zero).
*/
void rcu_idle_enter(void)
{
unsigned long flags;
long long oldval;
local_irq_save(flags);
oldval = rcu_dynticks_nesting;
rcu_dynticks_nesting = 0;
rcu_idle_enter_common(oldval);
local_irq_restore(flags);
}
/*
* Exit an interrupt handler towards idle.
*/
void rcu_irq_exit(void)
{
unsigned long flags;
long long oldval;
local_irq_save(flags);
oldval = rcu_dynticks_nesting;
rcu_dynticks_nesting--;
WARN_ON_ONCE(rcu_dynticks_nesting < 0);
rcu_idle_enter_common(oldval);
local_irq_restore(flags);
}
/* Common code for rcu_idle_exit() and rcu_irq_enter(), see kernel/rcutree.c. */
static void rcu_idle_exit_common(long long oldval)
{
if (oldval) {
RCU_TRACE(trace_rcu_dyntick("++=",
oldval, rcu_dynticks_nesting));
return;
}
RCU_TRACE(trace_rcu_dyntick("End", oldval, rcu_dynticks_nesting));
if (!is_idle_task(current)) {
struct task_struct *idle = idle_task(smp_processor_id());
RCU_TRACE(trace_rcu_dyntick("Error on exit: not idle task",
oldval, rcu_dynticks_nesting));
ftrace_dump(DUMP_ALL);
WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
current->pid, current->comm,
idle->pid, idle->comm); /* must be idle task! */
}
}
/*
* Exit idle, so that we are no longer in an extended quiescent state.
*/
void rcu_idle_exit(void)
{
unsigned long flags;
long long oldval;
local_irq_save(flags);
oldval = rcu_dynticks_nesting;
WARN_ON_ONCE(oldval != 0);
rcu_dynticks_nesting = DYNTICK_TASK_NESTING;
rcu_idle_exit_common(oldval);
local_irq_restore(flags);
}
/*
* Enter an interrupt handler, moving away from idle.
*/
void rcu_irq_enter(void)
{
unsigned long flags;
long long oldval;
local_irq_save(flags);
oldval = rcu_dynticks_nesting;
rcu_dynticks_nesting++;
WARN_ON_ONCE(rcu_dynticks_nesting == 0);
rcu_idle_exit_common(oldval);
local_irq_restore(flags);
}
#ifdef CONFIG_PROVE_RCU
/*
* Test whether RCU thinks that the current CPU is idle.
*/
int rcu_is_cpu_idle(void)
{
return !rcu_dynticks_nesting;
}
EXPORT_SYMBOL(rcu_is_cpu_idle);
#endif /* #ifdef CONFIG_PROVE_RCU */
/*
* Test whether the current CPU was interrupted from idle. Nested
* interrupts don't count, we must be running at the first interrupt
* level.
*/
int rcu_is_cpu_rrupt_from_idle(void)
{
return rcu_dynticks_nesting <= 0;
}
/*
* Helper function for rcu_sched_qs() and rcu_bh_qs().
* Also irqs are disabled to avoid confusion due to interrupt handlers
* invoking call_rcu().
*/
static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
{
if (rcp->rcucblist != NULL &&
rcp->donetail != rcp->curtail) {
rcp->donetail = rcp->curtail;
return 1;
}
return 0;
}
/*
* Record an rcu quiescent state. And an rcu_bh quiescent state while we
* are at it, given that any rcu quiescent state is also an rcu_bh
* quiescent state. Use "+" instead of "||" to defeat short circuiting.
*/
void rcu_sched_qs(int cpu)
{
unsigned long flags;
local_irq_save(flags);
if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
rcu_qsctr_help(&rcu_bh_ctrlblk))
invoke_rcu_callbacks();
local_irq_restore(flags);
}
/*
* Record an rcu_bh quiescent state.
*/
void rcu_bh_qs(int cpu)
{
unsigned long flags;
local_irq_save(flags);
if (rcu_qsctr_help(&rcu_bh_ctrlblk))
invoke_rcu_callbacks();
local_irq_restore(flags);
}
/*
* Check to see if the scheduling-clock interrupt came from an extended
* quiescent state, and, if so, tell RCU about it. This function must
* be called from hardirq context. It is normally called from the
* scheduling-clock interrupt.
*/
void rcu_check_callbacks(int cpu, int user)
{
if (user || rcu_is_cpu_rrupt_from_idle())
rcu_sched_qs(cpu);
else if (!in_softirq())
rcu_bh_qs(cpu);
rcu_preempt_check_callbacks();
}
/*
* Invoke the RCU callbacks on the specified rcu_ctrlkblk structure
* whose grace period has elapsed.
*/
static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
{
char *rn = NULL;
struct rcu_head *next, *list;
unsigned long flags;
RCU_TRACE(int cb_count = 0);
/* If no RCU callbacks ready to invoke, just return. */
if (&rcp->rcucblist == rcp->donetail) {
RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, -1));
RCU_TRACE(trace_rcu_batch_end(rcp->name, 0,
ACCESS_ONCE(rcp->rcucblist),
need_resched(),
is_idle_task(current),
rcu_is_callbacks_kthread()));
return;
}
/* Move the ready-to-invoke callbacks to a local list. */
local_irq_save(flags);
RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, -1));
list = rcp->rcucblist;
rcp->rcucblist = *rcp->donetail;
*rcp->donetail = NULL;
if (rcp->curtail == rcp->donetail)
rcp->curtail = &rcp->rcucblist;
rcu_preempt_remove_callbacks(rcp);
rcp->donetail = &rcp->rcucblist;
local_irq_restore(flags);
/* Invoke the callbacks on the local list. */
RCU_TRACE(rn = rcp->name);
while (list) {
next = list->next;
prefetch(next);
debug_rcu_head_unqueue(list);
local_bh_disable();
__rcu_reclaim(rn, list);
local_bh_enable();
list = next;
RCU_TRACE(cb_count++);
}
RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count));
RCU_TRACE(trace_rcu_batch_end(rcp->name, cb_count, 0, need_resched(),
is_idle_task(current),
rcu_is_callbacks_kthread()));
}
static void rcu_process_callbacks(struct softirq_action *unused)
{
__rcu_process_callbacks(&rcu_sched_ctrlblk);
__rcu_process_callbacks(&rcu_bh_ctrlblk);
rcu_preempt_process_callbacks();
}
/*
* Wait for a grace period to elapse. But it is illegal to invoke
* synchronize_sched() from within an RCU read-side critical section.
* Therefore, any legal call to synchronize_sched() is a quiescent
* state, and so on a UP system, synchronize_sched() need do nothing.
* Ditto for synchronize_rcu_bh(). (But Lai Jiangshan points out the
* benefits of doing might_sleep() to reduce latency.)
*
* Cool, huh? (Due to Josh Triplett.)
*
* But we want to make this a static inline later. The cond_resched()
* currently makes this problematic.
*/
void synchronize_sched(void)
{
cond_resched();
}
EXPORT_SYMBOL_GPL(synchronize_sched);
/*
* Helper function for call_rcu() and call_rcu_bh().
*/
static void __call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *rcu),
struct rcu_ctrlblk *rcp)
{
unsigned long flags;
debug_rcu_head_queue(head);
head->func = func;
head->next = NULL;
local_irq_save(flags);
*rcp->curtail = head;
rcp->curtail = &head->next;
RCU_TRACE(rcp->qlen++);
local_irq_restore(flags);
}
/*
* Post an RCU callback to be invoked after the end of an RCU-sched grace
* period. But since we have but one CPU, that would be after any
* quiescent state.
*/
void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
{
__call_rcu(head, func, &rcu_sched_ctrlblk);
}
EXPORT_SYMBOL_GPL(call_rcu_sched);
/*
* Post an RCU bottom-half callback to be invoked after any subsequent
* quiescent state.
*/
void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
{
__call_rcu(head, func, &rcu_bh_ctrlblk);
}
EXPORT_SYMBOL_GPL(call_rcu_bh);