From b2c0710c464ede15e1fc52fb1e7ee9ba54cea186 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 9 Sep 2010 13:40:39 -0700 Subject: rcu: move TINY_RCU from softirq to kthread If RCU priority boosting is to be meaningful, callback invocation must be boosted in addition to preempted RCU readers. Otherwise, in presence of CPU real-time threads, the grace period ends, but the callbacks don't get invoked. If the callbacks don't get invoked, the associated memory doesn't get freed, so the system is still subject to OOM. But it is not reasonable to priority-boost RCU_SOFTIRQ, so this commit moves the callback invocations to a kthread, which can be boosted easily. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- kernel/rcutiny_plugin.h | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) (limited to 'kernel/rcutiny_plugin.h') diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index 6ceca4f745ff..95f9239df512 100644 --- a/kernel/rcutiny_plugin.h +++ b/kernel/rcutiny_plugin.h @@ -22,6 +22,8 @@ * Author: Paul E. McKenney */ +#include + #ifdef CONFIG_TINY_PREEMPT_RCU #include @@ -164,9 +166,9 @@ static void rcu_preempt_cpu_qs(void) if (!rcu_preempt_blocked_readers_any()) rcu_preempt_ctrlblk.rcb.donetail = rcu_preempt_ctrlblk.nexttail; - /* If there are done callbacks, make RCU_SOFTIRQ process them. */ + /* If there are done callbacks, cause them to be invoked. */ if (*rcu_preempt_ctrlblk.rcb.donetail != NULL) - raise_softirq(RCU_SOFTIRQ); + invoke_rcu_cbs(); } /* @@ -374,7 +376,7 @@ static void rcu_preempt_check_callbacks(void) rcu_preempt_cpu_qs(); if (&rcu_preempt_ctrlblk.rcb.rcucblist != rcu_preempt_ctrlblk.rcb.donetail) - raise_softirq(RCU_SOFTIRQ); + invoke_rcu_cbs(); if (rcu_preempt_gp_in_progress() && rcu_cpu_blocking_cur_gp() && rcu_preempt_running_reader()) @@ -383,7 +385,7 @@ static void rcu_preempt_check_callbacks(void) /* * TINY_PREEMPT_RCU has an extra callback-list tail pointer to - * update, so this is invoked from __rcu_process_callbacks() to + * update, so this is invoked from rcu_process_callbacks() to * handle that case. Of course, it is invoked for all flavors of * RCU, but RCU callbacks can appear only on one of the lists, and * neither ->nexttail nor ->donetail can possibly be NULL, so there @@ -400,7 +402,7 @@ static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp) */ static void rcu_preempt_process_callbacks(void) { - __rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb); + rcu_process_callbacks(&rcu_preempt_ctrlblk.rcb); } /* @@ -599,14 +601,13 @@ static void rcu_preempt_process_callbacks(void) #endif /* #else #ifdef CONFIG_TINY_PREEMPT_RCU */ #ifdef CONFIG_DEBUG_LOCK_ALLOC - #include /* * During boot, we forgive RCU lockdep issues. After this function is * invoked, we start taking RCU lockdep issues seriously. */ -void rcu_scheduler_starting(void) +void __init rcu_scheduler_starting(void) { WARN_ON(nr_context_switches() > 0); rcu_scheduler_active = 1; -- cgit v1.2.2 From 24278d148316d2180be6df40e06db013d8b232b8 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 27 Sep 2010 17:25:23 -0700 Subject: rcu: priority boosting for TINY_PREEMPT_RCU Add priority boosting, but only for TINY_PREEMPT_RCU. This is enabled by the default-off RCU_BOOST kernel parameter. The priority to which to boost preempted RCU readers is controlled by the RCU_BOOST_PRIO kernel parameter (defaulting to real-time priority 1) and the time to wait before boosting the readers blocking a given grace period is controlled by the RCU_BOOST_DELAY kernel parameter (defaulting to 500 milliseconds). Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- kernel/rcutiny_plugin.h | 208 +++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 198 insertions(+), 10 deletions(-) (limited to 'kernel/rcutiny_plugin.h') diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index 95f9239df512..24f43165f222 100644 --- a/kernel/rcutiny_plugin.h +++ b/kernel/rcutiny_plugin.h @@ -24,6 +24,29 @@ #include +/* 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 @@ -48,17 +71,27 @@ struct rcu_preempt_ctrlblk { 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 = { @@ -123,6 +156,130 @@ static int rcu_preempt_gp_in_progress(void) return rcu_preempt_ctrlblk.completed != rcu_preempt_ctrlblk.gpnum; } +/* + * 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 @@ -150,12 +307,14 @@ static void rcu_preempt_cpu_qs(void) 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; @@ -168,7 +327,7 @@ static void rcu_preempt_cpu_qs(void) /* If there are done callbacks, cause them to be invoked. */ if (*rcu_preempt_ctrlblk.rcb.donetail != NULL) - invoke_rcu_cbs(); + invoke_rcu_kthread(); } /* @@ -186,6 +345,9 @@ static void rcu_preempt_start_gp(void) 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(); @@ -306,14 +468,16 @@ static void rcu_read_unlock_special(struct task_struct *t) */ 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); /* @@ -333,6 +497,14 @@ static void rcu_read_unlock_special(struct task_struct *t) 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); } @@ -376,7 +548,7 @@ static void rcu_preempt_check_callbacks(void) 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()) @@ -534,6 +706,7 @@ void synchronize_rcu_expedited(void) /* 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()); @@ -574,6 +747,15 @@ void exit_rcu(void) #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. @@ -614,3 +796,9 @@ void __init rcu_scheduler_starting(void) } #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 */ -- cgit v1.2.2 From 9e571a82f0cb205a65a0ea41657f19f22b7fabb8 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 30 Sep 2010 21:26:52 -0700 Subject: rcu: add tracing for TINY_RCU and TINY_PREEMPT_RCU Add tracing for the tiny RCU implementations, including statistics on boosting in the case of TINY_PREEMPT_RCU and RCU_BOOST. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- kernel/rcutiny_plugin.h | 232 +++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 222 insertions(+), 10 deletions(-) (limited to 'kernel/rcutiny_plugin.h') diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index 24f43165f222..f4e0df082d3c 100644 --- a/kernel/rcutiny_plugin.h +++ b/kernel/rcutiny_plugin.h @@ -23,12 +23,21 @@ */ #include +#include +#include + +#ifdef CONFIG_RCU_TRACE +#define RCU_TRACE(stmt) stmt +#else /* #ifdef CONFIG_RCU_TRACE */ +#define RCU_TRACE(stmt) +#endif /* #else #ifdef CONFIG_RCU_TRACE */ /* 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. */ }; /* Definition for rcupdate control block. */ @@ -90,8 +99,26 @@ struct rcu_preempt_ctrlblk { u8 gpcpu; /* Last grace period blocked by the CPU. */ u8 completed; /* Last grace period completed. */ /* If all three are equal, RCU is idle. */ +#ifdef CONFIG_RCU_BOOST s8 boosted_this_gp; /* Has boosting already happened? */ unsigned long boost_time; /* When to start boosting (jiffies) */ +#endif /* #ifdef CONFIG_RCU_BOOST */ +#ifdef CONFIG_RCU_TRACE + unsigned long n_grace_periods; +#ifdef CONFIG_RCU_BOOST + unsigned long n_tasks_boosted; + unsigned long n_exp_boosts; + unsigned long n_normal_boosts; + unsigned long n_normal_balk_blkd_tasks; + unsigned long n_normal_balk_gp_tasks; + unsigned long n_normal_balk_boost_tasks; + unsigned long n_normal_balk_boosted; + unsigned long n_normal_balk_notyet; + unsigned long n_normal_balk_nos; + unsigned long n_exp_balk_blkd_tasks; + unsigned long n_exp_balk_nos; +#endif /* #ifdef CONFIG_RCU_BOOST */ +#endif /* #ifdef CONFIG_RCU_TRACE */ }; static struct rcu_preempt_ctrlblk rcu_preempt_ctrlblk = { @@ -170,6 +197,65 @@ static struct list_head *rcu_next_node_entry(struct task_struct *t) return np; } +#ifdef CONFIG_RCU_TRACE + +#ifdef CONFIG_RCU_BOOST +static void rcu_initiate_boost_trace(void); +static void rcu_initiate_exp_boost_trace(void); +#endif /* #ifdef CONFIG_RCU_BOOST */ + +/* + * Dump additional statistice for TINY_PREEMPT_RCU. + */ +static void show_tiny_preempt_stats(struct seq_file *m) +{ + seq_printf(m, "rcu_preempt: qlen=%ld gp=%lu g%u/p%u/c%u tasks=%c%c%c\n", + rcu_preempt_ctrlblk.rcb.qlen, + rcu_preempt_ctrlblk.n_grace_periods, + rcu_preempt_ctrlblk.gpnum, + rcu_preempt_ctrlblk.gpcpu, + rcu_preempt_ctrlblk.completed, + "T."[list_empty(&rcu_preempt_ctrlblk.blkd_tasks)], + "N."[!rcu_preempt_ctrlblk.gp_tasks], + "E."[!rcu_preempt_ctrlblk.exp_tasks]); +#ifdef CONFIG_RCU_BOOST + seq_printf(m, " ttb=%c btg=", + "B."[!rcu_preempt_ctrlblk.boost_tasks]); + switch (rcu_preempt_ctrlblk.boosted_this_gp) { + case -1: + seq_puts(m, "exp"); + break; + case 0: + seq_puts(m, "no"); + break; + case 1: + seq_puts(m, "done"); + break; + default: + seq_printf(m, "?%d?", rcu_preempt_ctrlblk.boosted_this_gp); + } + seq_printf(m, " ntb=%lu neb=%lu nnb=%lu j=%04x bt=%04x\n", + rcu_preempt_ctrlblk.n_tasks_boosted, + rcu_preempt_ctrlblk.n_exp_boosts, + rcu_preempt_ctrlblk.n_normal_boosts, + (int)(jiffies & 0xffff), + (int)(rcu_preempt_ctrlblk.boost_time & 0xffff)); + seq_printf(m, " %s: nt=%lu gt=%lu bt=%lu b=%lu ny=%lu nos=%lu\n", + "normal balk", + rcu_preempt_ctrlblk.n_normal_balk_blkd_tasks, + rcu_preempt_ctrlblk.n_normal_balk_gp_tasks, + rcu_preempt_ctrlblk.n_normal_balk_boost_tasks, + rcu_preempt_ctrlblk.n_normal_balk_boosted, + rcu_preempt_ctrlblk.n_normal_balk_notyet, + rcu_preempt_ctrlblk.n_normal_balk_nos); + seq_printf(m, " exp balk: bt=%lu nos=%lu\n", + rcu_preempt_ctrlblk.n_exp_balk_blkd_tasks, + rcu_preempt_ctrlblk.n_exp_balk_nos); +#endif /* #ifdef CONFIG_RCU_BOOST */ +} + +#endif /* #ifdef CONFIG_RCU_TRACE */ + #ifdef CONFIG_RCU_BOOST #include "rtmutex_common.h" @@ -197,6 +283,7 @@ static int rcu_boost(void) t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BOOSTED; raw_local_irq_restore(flags); rt_mutex_lock(&mtx); + RCU_TRACE(rcu_preempt_ctrlblk.n_tasks_boosted++); rt_mutex_unlock(&mtx); return rcu_preempt_ctrlblk.boost_tasks != NULL; } @@ -206,16 +293,27 @@ static int rcu_boost(void) * 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. + * + * If there are no blocked readers blocking the current grace period, + * return 0 to let the caller know, otherwise return 1. Note that this + * return value is independent of whether or not boosting was done. */ -static void rcu_initiate_boost(void) +static int rcu_initiate_boost(void) { + if (!rcu_preempt_blocked_readers_cgp()) { + RCU_TRACE(rcu_preempt_ctrlblk.n_normal_balk_blkd_tasks++); + return 0; + } 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(); - } + RCU_TRACE(rcu_preempt_ctrlblk.n_normal_boosts++); + } else + RCU_TRACE(rcu_initiate_boost_trace()); + return 1; } /* @@ -231,7 +329,9 @@ static void rcu_initiate_expedited_boost(void) rcu_preempt_ctrlblk.blkd_tasks.next; rcu_preempt_ctrlblk.boosted_this_gp = -1; invoke_rcu_kthread(); - } + RCU_TRACE(rcu_preempt_ctrlblk.n_exp_boosts++); + } else + RCU_TRACE(rcu_initiate_exp_boost_trace()); raw_local_irq_restore(flags); } @@ -258,10 +358,13 @@ static int rcu_boost(void) } /* - * If there is no RCU priority boosting, we don't initiate boosting. + * If there is no RCU priority boosting, we don't initiate boosting, + * but we do indicate whether there are blocked readers blocking the + * current grace period. */ -static void rcu_initiate_boost(void) +static int rcu_initiate_boost(void) { + return rcu_preempt_blocked_readers_cgp(); } /* @@ -308,13 +411,14 @@ static void rcu_preempt_cpu_qs(void) current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; /* If there is no GP then there is nothing more to do. */ - if (!rcu_preempt_gp_in_progress() || rcu_preempt_blocked_readers_cgp()) + if (!rcu_preempt_gp_in_progress()) return; - /* If there are blocked readers, go check up on boosting. */ - if (rcu_preempt_blocked_readers_cgp()) { - rcu_initiate_boost(); + /* + * Check up on boosting. If there are no readers blocking the + * current grace period, leave. + */ + if (rcu_initiate_boost()) return; - } /* Advance callbacks. */ rcu_preempt_ctrlblk.completed = rcu_preempt_ctrlblk.gpnum; @@ -339,6 +443,7 @@ static void rcu_preempt_start_gp(void) /* Official start of GP. */ rcu_preempt_ctrlblk.gpnum++; + RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++); /* Any blocked RCU readers block new GP. */ if (rcu_preempt_blocked_readers_any()) @@ -591,6 +696,7 @@ void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) local_irq_save(flags); *rcu_preempt_ctrlblk.nexttail = head; rcu_preempt_ctrlblk.nexttail = &head->next; + RCU_TRACE(rcu_preempt_ctrlblk.rcb.qlen++); rcu_preempt_start_gp(); /* checks to see if GP needed. */ local_irq_restore(flags); } @@ -747,6 +853,18 @@ void exit_rcu(void) #else /* #ifdef CONFIG_TINY_PREEMPT_RCU */ +#ifdef CONFIG_RCU_TRACE + +/* + * Because preemptible RCU does not exist, it is not necessary to + * dump out its statistics. + */ +static void show_tiny_preempt_stats(struct seq_file *m) +{ +} + +#endif /* #ifdef CONFIG_RCU_TRACE */ + /* * Because preemptible RCU does not exist, it is never necessary to * boost preempted RCU readers. @@ -802,3 +920,97 @@ void __init rcu_scheduler_starting(void) #else /* #ifdef CONFIG_RCU_BOOST */ #define RCU_BOOST_PRIO 1 #endif /* #else #ifdef CONFIG_RCU_BOOST */ + +#ifdef CONFIG_RCU_TRACE + +#ifdef CONFIG_RCU_BOOST + +static void rcu_initiate_boost_trace(void) +{ + if (rcu_preempt_ctrlblk.gp_tasks == NULL) + rcu_preempt_ctrlblk.n_normal_balk_gp_tasks++; + else if (rcu_preempt_ctrlblk.boost_tasks != NULL) + rcu_preempt_ctrlblk.n_normal_balk_boost_tasks++; + else if (rcu_preempt_ctrlblk.boosted_this_gp != 0) + rcu_preempt_ctrlblk.n_normal_balk_boosted++; + else if (!ULONG_CMP_GE(jiffies, rcu_preempt_ctrlblk.boost_time)) + rcu_preempt_ctrlblk.n_normal_balk_notyet++; + else + rcu_preempt_ctrlblk.n_normal_balk_nos++; +} + +static void rcu_initiate_exp_boost_trace(void) +{ + if (list_empty(&rcu_preempt_ctrlblk.blkd_tasks)) + rcu_preempt_ctrlblk.n_exp_balk_blkd_tasks++; + else + rcu_preempt_ctrlblk.n_exp_balk_nos++; +} + +#endif /* #ifdef CONFIG_RCU_BOOST */ + +static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) +{ + unsigned long flags; + + raw_local_irq_save(flags); + rcp->qlen -= n; + raw_local_irq_restore(flags); +} + +/* + * Dump statistics for TINY_RCU, such as they are. + */ +static int show_tiny_stats(struct seq_file *m, void *unused) +{ + show_tiny_preempt_stats(m); + seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen); + seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen); + return 0; +} + +static int show_tiny_stats_open(struct inode *inode, struct file *file) +{ + return single_open(file, show_tiny_stats, NULL); +} + +static const struct file_operations show_tiny_stats_fops = { + .owner = THIS_MODULE, + .open = show_tiny_stats_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + +static struct dentry *rcudir; + +static int __init rcutiny_trace_init(void) +{ + struct dentry *retval; + + rcudir = debugfs_create_dir("rcu", NULL); + if (!rcudir) + goto free_out; + retval = debugfs_create_file("rcudata", 0444, rcudir, + NULL, &show_tiny_stats_fops); + if (!retval) + goto free_out; + return 0; +free_out: + debugfs_remove_recursive(rcudir); + return 1; +} + +static void __exit rcutiny_trace_cleanup(void) +{ + debugfs_remove_recursive(rcudir); +} + +module_init(rcutiny_trace_init); +module_exit(rcutiny_trace_cleanup); + +MODULE_AUTHOR("Paul E. McKenney"); +MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation"); +MODULE_LICENSE("GPL"); + +#endif /* #ifdef CONFIG_RCU_TRACE */ -- cgit v1.2.2 From e940cc804ec212e483f91167b93d1740c2fd3415 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 4 Nov 2010 14:55:26 -0700 Subject: rcu: Distinguish between boosting and boosted RCU priority boosting's tracing did not distinguish between ongoing boosting and completion of boosting. This commit therefore adds this capability. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- kernel/rcutiny_plugin.h | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'kernel/rcutiny_plugin.h') diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index f4e0df082d3c..015abaea962a 100644 --- a/kernel/rcutiny_plugin.h +++ b/kernel/rcutiny_plugin.h @@ -229,6 +229,9 @@ static void show_tiny_preempt_stats(struct seq_file *m) seq_puts(m, "no"); break; case 1: + seq_puts(m, "begun"); + break; + case 2: seq_puts(m, "done"); break; default: @@ -284,6 +287,7 @@ static int rcu_boost(void) raw_local_irq_restore(flags); rt_mutex_lock(&mtx); RCU_TRACE(rcu_preempt_ctrlblk.n_tasks_boosted++); + rcu_preempt_ctrlblk.boosted_this_gp++; rt_mutex_unlock(&mtx); return rcu_preempt_ctrlblk.boost_tasks != NULL; } -- cgit v1.2.2