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rcu: Remove RCU CPU stall warnings from Tiny RCU

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Tiny RCU's job is to be tiny, so this commit removes its RCU CPU
stall warning code.  After this, there is no longer any need for
rcu_sched_ctrlblk and rcu_bh_ctrlblk to be in tiny_plugin.h, so this
commit also moves them to tiny.c.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2017-05-17 10:54:29 -07:00
parent c23484f0e7
commit 6d48152eaf
4 changed files with 19 additions and 97 deletions
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2
kernel/rcu/Kconfig
View file

@ -78,7 +78,7 @@ config TASKS_RCU
user-mode execution as quiescent states.
config RCU_STALL_COMMON
def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
def_bool ( TREE_RCU || PREEMPT_RCU )
help
This option enables RCU CPU stall code that is common between
the TINY and TREE variants of RCU. The purpose is to allow

35
kernel/rcu/tiny.c
View file

@ -38,11 +38,23 @@
#include "rcu.h"
/* Forward declarations for tiny_plugin.h. */
struct rcu_ctrlblk;
static void __call_rcu(struct rcu_head *head,
rcu_callback_t func,
struct rcu_ctrlblk *rcp);
/* Global control variables for rcupdate callback mechanism. */
struct rcu_ctrlblk {
struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */
struct rcu_head **donetail; /* ->next pointer of last "done" CB. */
struct rcu_head **curtail; /* ->next pointer of last CB. */
};
/* Definition for rcupdate control block. */
static struct rcu_ctrlblk rcu_sched_ctrlblk = {
.donetail = &rcu_sched_ctrlblk.rcucblist,
.curtail = &rcu_sched_ctrlblk.rcucblist,
};
static struct rcu_ctrlblk rcu_bh_ctrlblk = {
.donetail = &rcu_bh_ctrlblk.rcucblist,
.curtail = &rcu_bh_ctrlblk.rcucblist,
};
#include "tiny_plugin.h"
@ -65,7 +77,6 @@ EXPORT_SYMBOL(rcu_barrier_sched);
*/
static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
{
RCU_TRACE(reset_cpu_stall_ticks(rcp);)
if (rcp->donetail != rcp->curtail) {
rcp->donetail = rcp->curtail;
return 1;
@ -111,7 +122,6 @@ void rcu_bh_qs(void)
*/
void rcu_check_callbacks(int user)
{
RCU_TRACE(check_cpu_stalls();)
if (user)
rcu_sched_qs();
else if (!in_softirq())
@ -126,10 +136,8 @@ void rcu_check_callbacks(int user)
*/
static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
{
const char *rn = NULL;
struct rcu_head *next, *list;
unsigned long flags;
RCU_TRACE(int cb_count = 0;)
/* Move the ready-to-invoke callbacks to a local list. */
local_irq_save(flags);
@ -147,18 +155,15 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
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);
__rcu_reclaim("", list);
local_bh_enable();
list = next;
RCU_TRACE(cb_count++;)
}
RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count);)
}
static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused)
@ -202,7 +207,6 @@ static void __call_rcu(struct rcu_head *head,
local_irq_save(flags);
*rcp->curtail = head;
rcp->curtail = &head->next;
RCU_TRACE(rcp->qlen++;)
local_irq_restore(flags);
if (unlikely(is_idle_task(current))) {
@ -235,8 +239,5 @@ EXPORT_SYMBOL_GPL(call_rcu_bh);
void __init rcu_init(void)
{
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
RCU_TRACE(reset_cpu_stall_ticks(&rcu_sched_ctrlblk);)
RCU_TRACE(reset_cpu_stall_ticks(&rcu_bh_ctrlblk);)
rcu_early_boot_tests();
}

78
kernel/rcu/tiny_plugin.h
View file

@ -22,34 +22,6 @@
* Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*/
#include <linux/kthread.h>
#include <linux/init.h>
/* Global control variables for rcupdate callback mechanism. */
struct rcu_ctrlblk {
struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */
struct rcu_head **donetail; /* ->next pointer of last "done" CB. */
struct rcu_head **curtail; /* ->next pointer of last CB. */
RCU_TRACE(long qlen); /* Number of pending CBs. */
RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */
RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */
RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */
RCU_TRACE(const char *name); /* Name of RCU type. */
};
/* Definition for rcupdate control block. */
static struct rcu_ctrlblk rcu_sched_ctrlblk = {
.donetail = &rcu_sched_ctrlblk.rcucblist,
.curtail = &rcu_sched_ctrlblk.rcucblist,
RCU_TRACE(.name = "rcu_sched")
};
static struct rcu_ctrlblk rcu_bh_ctrlblk = {
.donetail = &rcu_bh_ctrlblk.rcucblist,
.curtail = &rcu_bh_ctrlblk.rcucblist,
RCU_TRACE(.name = "rcu_bh")
};
#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU)
#include <linux/kernel_stat.h>
@ -73,53 +45,3 @@ void __init rcu_scheduler_starting(void)
}
#endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU) */
#ifdef CONFIG_RCU_TRACE
static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
{
unsigned long flags;
local_irq_save(flags);
rcp->qlen -= n;
local_irq_restore(flags);
}
static void check_cpu_stall(struct rcu_ctrlblk *rcp)
{
unsigned long j;
unsigned long js;
if (rcu_cpu_stall_suppress)
return;
rcp->ticks_this_gp++;
j = jiffies;
js = READ_ONCE(rcp->jiffies_stall);
if (rcp->rcucblist && ULONG_CMP_GE(j, js)) {
pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
rcp->name, rcp->ticks_this_gp, DYNTICK_TASK_EXIT_IDLE,
jiffies - rcp->gp_start, rcp->qlen);
dump_stack();
WRITE_ONCE(rcp->jiffies_stall,
jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
} else if (ULONG_CMP_GE(j, js)) {
WRITE_ONCE(rcp->jiffies_stall,
jiffies + rcu_jiffies_till_stall_check());
}
}
static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
{
rcp->ticks_this_gp = 0;
rcp->gp_start = jiffies;
WRITE_ONCE(rcp->jiffies_stall,
jiffies + rcu_jiffies_till_stall_check());
}
static void check_cpu_stalls(void)
{
RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk);)
RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk);)
}
#endif /* #ifdef CONFIG_RCU_TRACE */

1
tools/testing/selftests/rcutorture/configs/rcu/TINY02
View file

@ -6,7 +6,6 @@ CONFIG_PREEMPT=n
CONFIG_HZ_PERIODIC=y
CONFIG_NO_HZ_IDLE=n
CONFIG_NO_HZ_FULL=n
CONFIG_RCU_TRACE=y
CONFIG_PROVE_LOCKING=y
#CHECK#CONFIG_PROVE_RCU=y
CONFIG_DEBUG_LOCK_ALLOC=y