From 9fdd3bc9005824704f9802bec7b3e06f5edae434 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 29 Jul 2014 14:50:47 -0700 Subject: rcu: Break more call_rcu() deadlock involving scheduler and perf Commit 96d3fd0d315a9 (rcu: Break call_rcu() deadlock involving scheduler and perf) covered the case where __call_rcu_nocb_enqueue() needs to wake the rcuo kthread due to the queue being initially empty, but did not do anything for the case where the queue was overflowing. This commit therefore also defers wakeup for the overflow case. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.h | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'kernel/rcu/tree.h') diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 6a86eb7..e33562f 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -350,7 +350,7 @@ struct rcu_data { int nocb_p_count_lazy; /* (approximate). */ wait_queue_head_t nocb_wq; /* For nocb kthreads to sleep on. */ struct task_struct *nocb_kthread; - bool nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ + int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */ /* The following fields are used by the leader, hence own cacheline. */ struct rcu_head *nocb_gp_head ____cacheline_internodealigned_in_smp; @@ -383,6 +383,11 @@ struct rcu_data { #define RCU_FORCE_QS 3 /* Need to force quiescent state. */ #define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK +/* Values for nocb_defer_wakeup field in struct rcu_data. */ +#define RCU_NOGP_WAKE_NOT 0 +#define RCU_NOGP_WAKE 1 +#define RCU_NOGP_WAKE_FORCE 2 + #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) /* For jiffies_till_first_fqs and */ /* and jiffies_till_next_fqs. */ @@ -589,7 +594,7 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, struct rcu_data *rdp, unsigned long flags); -static bool rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); +static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); static void do_nocb_deferred_wakeup(struct rcu_data *rdp); static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); static void rcu_spawn_nocb_kthreads(struct rcu_state *rsp); -- cgit v1.1 From 9386c0b75dda05f535a10ea1abf1817fe292c81c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 13 Jul 2014 12:00:53 -0700 Subject: rcu: Rationalize kthread spawning Currently, RCU spawns kthreads from several different early_initcall() functions. Although this has served RCU well for quite some time, as more kthreads are added a more deterministic approach is required. This commit therefore causes all of RCU's early-boot kthreads to be spawned from a single early_initcall() function. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett Tested-by: Paul Gortmaker --- kernel/rcu/tree.h | 1 + 1 file changed, 1 insertion(+) (limited to 'kernel/rcu/tree.h') diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 6a86eb7..a966092 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -572,6 +572,7 @@ static void rcu_preempt_do_callbacks(void); static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp, struct rcu_node *rnp); #endif /* #ifdef CONFIG_RCU_BOOST */ +static void __init rcu_spawn_boost_kthreads(void); static void rcu_prepare_kthreads(int cpu); static void rcu_cleanup_after_idle(int cpu); static void rcu_prepare_for_idle(int cpu); -- cgit v1.1 From 35ce7f29a44a888c45c0a9f202f69e10613c5306 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 11 Jul 2014 11:30:24 -0700 Subject: rcu: Create rcuo kthreads only for onlined CPUs RCU currently uses for_each_possible_cpu() to spawn rcuo kthreads, which can result in more rcuo kthreads than one would expect, for example, derRichard reported 64 CPUs worth of rcuo kthreads on an 8-CPU image. This commit therefore creates rcuo kthreads only for those CPUs that actually come online. This was reported by derRichard on the OFTC IRC network. Reported-by: Richard Weinberger Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett Tested-by: Paul Gortmaker --- kernel/rcu/tree.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'kernel/rcu/tree.h') diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index a966092..a9a226d 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -593,7 +593,11 @@ static bool rcu_nocb_adopt_orphan_cbs(struct rcu_state *rsp, static bool rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp); static void do_nocb_deferred_wakeup(struct rcu_data *rdp); static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp); -static void rcu_spawn_nocb_kthreads(struct rcu_state *rsp); +static void rcu_spawn_all_nocb_kthreads(int cpu); +static void __init rcu_spawn_nocb_kthreads(void); +#ifdef CONFIG_RCU_NOCB_CPU +static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp); +#endif /* #ifdef CONFIG_RCU_NOCB_CPU */ static void __maybe_unused rcu_kick_nohz_cpu(int cpu); static bool init_nocb_callback_list(struct rcu_data *rdp); static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq); -- cgit v1.1