#include <linux/time.h>
#include <linux/cpu.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. */
-};
-
-/* 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,
-};
-
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-int rcu_scheduler_active __read_mostly;
-EXPORT_SYMBOL_GPL(rcu_scheduler_active);
-#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
-
-/* Controls for rcu_cbs() kthread, replacing RCU_SOFTIRQ used previously. */
-static struct task_struct *rcu_cbs_task;
-static DECLARE_WAIT_QUEUE_HEAD(rcu_cbs_wq);
-static unsigned long have_rcu_cbs;
-static void invoke_rcu_cbs(void);
+/* Controls for rcu_kthread() kthread, replacing RCU_SOFTIRQ used previously. */
+static struct task_struct *rcu_kthread_task;
+static DECLARE_WAIT_QUEUE_HEAD(rcu_kthread_wq);
+static unsigned long have_rcu_kthread_work;
+static void invoke_rcu_kthread(void);
/* Forward declarations for rcutiny_plugin.h. */
+struct rcu_ctrlblk;
static void rcu_process_callbacks(struct rcu_ctrlblk *rcp);
-static int rcu_cbs(void *arg);
+static int rcu_kthread(void *arg);
static void __call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *rcu),
struct rcu_ctrlblk *rcp);
{
if (rcu_qsctr_help(&rcu_sched_ctrlblk) +
rcu_qsctr_help(&rcu_bh_ctrlblk))
- invoke_rcu_cbs();
+ invoke_rcu_kthread();
}
/*
void rcu_bh_qs(int cpu)
{
if (rcu_qsctr_help(&rcu_bh_ctrlblk))
- invoke_rcu_cbs();
+ invoke_rcu_kthread();
}
/*
* This is a kthread, but it is never stopped, at least not until
* the system goes down.
*/
-static int rcu_cbs(void *arg)
+static int rcu_kthread(void *arg)
{
unsigned long work;
+ unsigned long morework;
unsigned long flags;
for (;;) {
- wait_event(rcu_cbs_wq, have_rcu_cbs != 0);
+ wait_event(rcu_kthread_wq, have_rcu_kthread_work != 0);
+ morework = rcu_boost();
local_irq_save(flags);
- work = have_rcu_cbs;
- have_rcu_cbs = 0;
+ work = have_rcu_kthread_work;
+ have_rcu_kthread_work = morework;
local_irq_restore(flags);
if (work) {
rcu_process_callbacks(&rcu_sched_ctrlblk);
rcu_process_callbacks(&rcu_bh_ctrlblk);
rcu_preempt_process_callbacks();
}
+ schedule_timeout_interruptible(1); /* Leave CPU for others. */
}
return 0; /* Not reached, but needed to shut gcc up. */
}
/*
- * Wake up rcu_cbs() to process callbacks now eligible for invocation.
+ * Wake up rcu_kthread() to process callbacks now eligible for invocation
+ * or to boost readers.
*/
-static void invoke_rcu_cbs(void)
+static void invoke_rcu_kthread(void)
{
unsigned long flags;
local_irq_save(flags);
- have_rcu_cbs = 1;
- wake_up(&rcu_cbs_wq);
+ have_rcu_kthread_work = 1;
+ wake_up(&rcu_kthread_wq);
local_irq_restore(flags);
}
*/
static int __init rcu_spawn_kthreads(void)
{
- rcu_cbs_task = kthread_run(rcu_cbs, NULL, "rcu_cbs");
+ struct sched_param sp;
+
+ rcu_kthread_task = kthread_run(rcu_kthread, NULL, "rcu_kthread");
+ sp.sched_priority = RCU_BOOST_PRIO;
+ sched_setscheduler_nocheck(rcu_kthread_task, SCHED_FIFO, &sp);
return 0;
}
early_initcall(rcu_spawn_kthreads);
#include <linux/kthread.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. */
+};
+
+/* 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,
+};
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+int rcu_scheduler_active __read_mostly;
+EXPORT_SYMBOL_GPL(rcu_scheduler_active);
+#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
#ifdef CONFIG_TINY_PREEMPT_RCU
#include <linux/delay.h>
struct list_head *gp_tasks;
/* Pointer to the first task blocking the */
/* current grace period, or NULL if there */
- /* is not such task. */
+ /* is no such task. */
struct list_head *exp_tasks;
/* Pointer to first task blocking the */
/* current expedited grace period, or NULL */
/* if there is no such task. If there */
/* is no current expedited grace period, */
/* then there cannot be any such task. */
+#ifdef CONFIG_RCU_BOOST
+ struct list_head *boost_tasks;
+ /* Pointer to first task that needs to be */
+ /* priority-boosted, or NULL if no priority */
+ /* boosting is needed. If there is no */
+ /* current or expedited grace period, there */
+ /* can be no such task. */
+#endif /* #ifdef CONFIG_RCU_BOOST */
u8 gpnum; /* Current grace period. */
u8 gpcpu; /* Last grace period blocked by the CPU. */
u8 completed; /* Last grace period completed. */
/* If all three are equal, RCU is idle. */
+ s8 boosted_this_gp; /* Has boosting already happened? */
+ unsigned long boost_time; /* When to start boosting (jiffies) */
};
static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = {
}
/*
+ * Advance a ->blkd_tasks-list pointer to the next entry, instead
+ * returning NULL if at the end of the list.
+ */
+static struct list_head *rcu_next_node_entry(struct task_struct *t)
+{
+ struct list_head *np;
+
+ np = t->rcu_node_entry.next;
+ if (np == &rcu_preempt_ctrlblk.blkd_tasks)
+ np = NULL;
+ return np;
+}
+
+#ifdef CONFIG_RCU_BOOST
+
+#include "rtmutex_common.h"
+
+/*
+ * Carry out RCU priority boosting on the task indicated by ->boost_tasks,
+ * and advance ->boost_tasks to the next task in the ->blkd_tasks list.
+ */
+static int rcu_boost(void)
+{
+ unsigned long flags;
+ struct rt_mutex mtx;
+ struct list_head *np;
+ struct task_struct *t;
+
+ if (rcu_preempt_ctrlblk.boost_tasks == NULL)
+ return 0; /* Nothing to boost. */
+ raw_local_irq_save(flags);
+ rcu_preempt_ctrlblk.boosted_this_gp++;
+ t = container_of(rcu_preempt_ctrlblk.boost_tasks, struct task_struct,
+ rcu_node_entry);
+ np = rcu_next_node_entry(t);
+ rt_mutex_init_proxy_locked(&mtx, t);
+ t->rcu_boost_mutex = &mtx;
+ t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BOOSTED;
+ raw_local_irq_restore(flags);
+ rt_mutex_lock(&mtx);
+ rt_mutex_unlock(&mtx);
+ return rcu_preempt_ctrlblk.boost_tasks != NULL;
+}
+
+/*
+ * Check to see if it is now time to start boosting RCU readers blocking
+ * the current grace period, and, if so, tell the rcu_kthread_task to
+ * start boosting them. If there is an expedited boost in progress,
+ * we wait for it to complete.
+ */
+static void rcu_initiate_boost(void)
+{
+ if (rcu_preempt_ctrlblk.gp_tasks != NULL &&
+ rcu_preempt_ctrlblk.boost_tasks == NULL &&
+ rcu_preempt_ctrlblk.boosted_this_gp == 0 &&
+ ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time)) {
+ rcu_preempt_ctrlblk.boost_tasks = rcu_preempt_ctrlblk.gp_tasks;
+ invoke_rcu_kthread();
+ }
+}
+
+/*
+ * Initiate boosting for an expedited grace period.
+ */
+static void rcu_initiate_expedited_boost(void)
+{
+ unsigned long flags;
+
+ raw_local_irq_save(flags);
+ if (!list_empty(&rcu_preempt_ctrlblk.blkd_tasks)) {
+ rcu_preempt_ctrlblk.boost_tasks =
+ rcu_preempt_ctrlblk.blkd_tasks.next;
+ rcu_preempt_ctrlblk.boosted_this_gp = -1;
+ invoke_rcu_kthread();
+ }
+ raw_local_irq_restore(flags);
+}
+
+#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000);
+
+/*
+ * Do priority-boost accounting for the start of a new grace period.
+ */
+static void rcu_preempt_boost_start_gp(void)
+{
+ rcu_preempt_ctrlblk.boost_time = jiffies + RCU_BOOST_DELAY_JIFFIES;
+ if (rcu_preempt_ctrlblk.boosted_this_gp > 0)
+ rcu_preempt_ctrlblk.boosted_this_gp = 0;
+}
+
+#else /* #ifdef CONFIG_RCU_BOOST */
+
+/*
+ * If there is no RCU priority boosting, we don't boost.
+ */
+static int rcu_boost(void)
+{
+ return 0;
+}
+
+/*
+ * If there is no RCU priority boosting, we don't initiate boosting.
+ */
+static void rcu_initiate_boost(void)
+{
+}
+
+/*
+ * If there is no RCU priority boosting, we don't initiate expedited boosting.
+ */
+static void rcu_initiate_expedited_boost(void)
+{
+}
+
+/*
+ * If there is no RCU priority boosting, nothing to do at grace-period start.
+ */
+static void rcu_preempt_boost_start_gp(void)
+{
+}
+
+#endif /* else #ifdef CONFIG_RCU_BOOST */
+
+/*
* Record a preemptible-RCU quiescent state for the specified CPU. Note
* that this just means that the task currently running on the CPU is
* in a quiescent state. There might be any number of tasks blocked
rcu_preempt_ctrlblk.gpcpu = rcu_preempt_ctrlblk.gpnum;
current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
- /*
- * If there is no GP, or if blocked readers are still blocking GP,
- * then there is nothing more to do.
- */
+ /* If there is no GP then there is nothing more to do. */
if (!rcu_preempt_gp_in_progress() || rcu_preempt_blocked_readers_cgp())
return;
+ /* If there are blocked readers, go check up on boosting. */
+ if (rcu_preempt_blocked_readers_cgp()) {
+ rcu_initiate_boost();
+ return;
+ }
/* Advance callbacks. */
rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum;
/* If there are done callbacks, cause them to be invoked. */
if (*rcu_preempt_ctrlblk.rcb.donetail != NULL)
- invoke_rcu_cbs();
+ invoke_rcu_kthread();
}
/*
rcu_preempt_ctrlblk.gp_tasks =
rcu_preempt_ctrlblk.blkd_tasks.next;
+ /* Set up for RCU priority boosting. */
+ rcu_preempt_boost_start_gp();
+
/* If there is no running reader, CPU is done with GP. */
if (!rcu_preempt_running_reader())
rcu_preempt_cpu_qs();
*/
empty = !rcu_preempt_blocked_readers_cgp();
empty_exp = rcu_preempt_ctrlblk.exp_tasks == NULL;
- np = t->rcu_node_entry.next;
- if (np == &rcu_preempt_ctrlblk.blkd_tasks)
- np = NULL;
+ np = rcu_next_node_entry(t);
list_del(&t->rcu_node_entry);
if (&t->rcu_node_entry == rcu_preempt_ctrlblk.gp_tasks)
rcu_preempt_ctrlblk.gp_tasks = np;
if (&t->rcu_node_entry == rcu_preempt_ctrlblk.exp_tasks)
rcu_preempt_ctrlblk.exp_tasks = np;
+#ifdef CONFIG_RCU_BOOST
+ if (&t->rcu_node_entry == rcu_preempt_ctrlblk.boost_tasks)
+ rcu_preempt_ctrlblk.boost_tasks = np;
+#endif /* #ifdef CONFIG_RCU_BOOST */
INIT_LIST_HEAD(&t->rcu_node_entry);
/*
if (!empty_exp && rcu_preempt_ctrlblk.exp_tasks == NULL)
rcu_report_exp_done();
}
+#ifdef CONFIG_RCU_BOOST
+ /* Unboost self if was boosted. */
+ if (special & RCU_READ_UNLOCK_BOOSTED) {
+ t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BOOSTED;
+ rt_mutex_unlock(t->rcu_boost_mutex);
+ t->rcu_boost_mutex = NULL;
+ }
+#endif /* #ifdef CONFIG_RCU_BOOST */
local_irq_restore(flags);
}
rcu_preempt_cpu_qs();
if (&rcu_preempt_ctrlblk.rcb.rcucblist !=
rcu_preempt_ctrlblk.rcb.donetail)
- invoke_rcu_cbs();
+ invoke_rcu_kthread();
if (rcu_preempt_gp_in_progress() &&
rcu_cpu_blocking_cur_gp() &&
rcu_preempt_running_reader())
/* Wait for tail of ->blkd_tasks list to drain. */
if (rcu_preempted_readers_exp())
+ rcu_initiate_expedited_boost();
wait_event(sync_rcu_preempt_exp_wq,
!rcu_preempted_readers_exp());
#else /* #ifdef CONFIG_TINY_PREEMPT_RCU */
/*
+ * Because preemptible RCU does not exist, it is never necessary to
+ * boost preempted RCU readers.
+ */
+static int rcu_boost(void)
+{
+ return 0;
+}
+
+/*
* Because preemptible RCU does not exist, it never has any callbacks
* to check.
*/
}
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+#ifdef CONFIG_RCU_BOOST
+#define RCU_BOOST_PRIO CONFIG_RCU_BOOST_PRIO
+#else /* #ifdef CONFIG_RCU_BOOST */
+#define RCU_BOOST_PRIO 1
+#endif /* #else #ifdef CONFIG_RCU_BOOST */
projects / linux-flexiantxendom0-natty.git / commitdiff