rcu: Remove RCU CPU stall warnings from Tiny RCU

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>

diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index 8edff43e8e94d00092e77b56c862fbf10c79fb67..be90c945063f46b7ba1368aed5c6fc970e9b6e98 100644 (file)
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -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

diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index 595cb1bf944f02158b72077b68a620d0adaa8f41..f8488965250f12ce26d40ba31553b8128ef55023 100644 (file)
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -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();
 }

diff --git a/kernel/rcu/tiny_plugin.h b/kernel/rcu/tiny_plugin.h
index c642f23f1582e857e937967a5bcd039cf124bab7..f0a01b2a30623e70cc8e05d112b29c521b0db435 100644 (file)
--- a/kernel/rcu/tiny_plugin.h
+++ b/kernel/rcu/tiny_plugin.h
@@ -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 */

diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TINY02 b/tools/testing/selftests/rcutorture/configs/rcu/TINY02
index 1f6bebbf5da80a12ecaf8c7bad93cff806365a0c..d8674264318d677acbe3807de7f31ea00d3fedd8 100644 (file)
--- a/tools/testing/selftests/rcutorture/configs/rcu/TINY02
+++ b/tools/testing/selftests/rcutorture/configs/rcu/TINY02
@@ -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