From 4e6ea4ef56f9425cd239ffdb6be45b3aeeb347fd Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 14 Aug 2018 14:41:49 -0700 Subject: [PATCH] srcu: Make early-boot call_srcu() reuse workqueue lists Allocating a list_head structure that is almost never used, and, when used, is used only during early boot (rcu_init() and earlier), is a bit wasteful. This commit therefore eliminates that list_head in favor of the one in the work_struct structure. This is safe because the work_struct structure cannot be used until after rcu_init() returns. Reported-by: Steven Rostedt Signed-off-by: Paul E. McKenney Cc: Tejun Heo Cc: Lai Jiangshan Tested-by: Steven Rostedt (VMware) --- include/linux/srcutiny.h | 2 -- include/linux/srcutree.h | 3 +-- kernel/rcu/srcutiny.c | 10 +++++----- kernel/rcu/srcutree.c | 11 +++++------ 4 files changed, 11 insertions(+), 15 deletions(-) diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index 2b5c0822e683..f41d2fb09f87 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -36,7 +36,6 @@ struct srcu_struct { struct rcu_head *srcu_cb_head; /* Pending callbacks: Head. */ struct rcu_head **srcu_cb_tail; /* Pending callbacks: Tail. */ struct work_struct srcu_work; /* For driving grace periods. */ - struct list_head srcu_boot_entry; /* Early-boot callbacks. */ #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -49,7 +48,6 @@ void srcu_drive_gp(struct work_struct *wp); .srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \ .srcu_cb_tail = &name.srcu_cb_head, \ .srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \ - .srcu_boot_entry = LIST_HEAD_INIT(name.srcu_boot_entry), \ __SRCU_DEP_MAP_INIT(name) \ } diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 9cfa4610113a..0ae91b3a7406 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -94,7 +94,6 @@ struct srcu_struct { /* callback for the barrier */ /* operation. */ struct delayed_work work; - struct list_head srcu_boot_entry; /* Early-boot callbacks. */ #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ @@ -110,7 +109,7 @@ struct srcu_struct { .sda = &pcpu_name, \ .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ .srcu_gp_seq_needed = -1UL, \ - .srcu_boot_entry = LIST_HEAD_INIT(name.srcu_boot_entry), \ + .work = __DELAYED_WORK_INITIALIZER(name.work, NULL, 0), \ __SRCU_DEP_MAP_INIT(name) \ } diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index d233f0c63f6f..b46e6683f8c9 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -48,7 +48,7 @@ static int init_srcu_struct_fields(struct srcu_struct *sp) sp->srcu_gp_waiting = false; sp->srcu_idx = 0; INIT_WORK(&sp->srcu_work, srcu_drive_gp); - INIT_LIST_HEAD(&sp->srcu_boot_entry); + INIT_LIST_HEAD(&sp->srcu_work.entry); return 0; } @@ -185,8 +185,8 @@ void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, if (!READ_ONCE(sp->srcu_gp_running)) { if (likely(srcu_init_done)) schedule_work(&sp->srcu_work); - else if (list_empty(&sp->srcu_boot_entry)) - list_add(&sp->srcu_boot_entry, &srcu_boot_list); + else if (list_empty(&sp->srcu_work.entry)) + list_add(&sp->srcu_work.entry, &srcu_boot_list); } } EXPORT_SYMBOL_GPL(call_srcu); @@ -224,8 +224,8 @@ void __init srcu_init(void) srcu_init_done = true; while (!list_empty(&srcu_boot_list)) { sp = list_first_entry(&srcu_boot_list, - struct srcu_struct, srcu_boot_entry); - list_del_init(&sp->srcu_boot_entry); + struct srcu_struct, srcu_work.entry); + list_del_init(&sp->srcu_work.entry); schedule_work(&sp->srcu_work); } } diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 2e7f6b460150..86c7fd0a1bfe 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -186,7 +186,6 @@ static int init_srcu_struct_fields(struct srcu_struct *sp, bool is_static) mutex_init(&sp->srcu_barrier_mutex); atomic_set(&sp->srcu_barrier_cpu_cnt, 0); INIT_DELAYED_WORK(&sp->work, process_srcu); - INIT_LIST_HEAD(&sp->srcu_boot_entry); if (!is_static) sp->sda = alloc_percpu(struct srcu_data); init_srcu_struct_nodes(sp, is_static); @@ -708,8 +707,8 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, if (likely(srcu_init_done)) queue_delayed_work(rcu_gp_wq, &sp->work, srcu_get_delay(sp)); - else if (list_empty(&sp->srcu_boot_entry)) - list_add(&sp->srcu_boot_entry, &srcu_boot_list); + else if (list_empty(&sp->work.work.entry)) + list_add(&sp->work.work.entry, &srcu_boot_list); } spin_unlock_irqrestore_rcu_node(sp, flags); } @@ -1323,10 +1322,10 @@ void __init srcu_init(void) srcu_init_done = true; while (!list_empty(&srcu_boot_list)) { - sp = list_first_entry(&srcu_boot_list, - struct srcu_struct, srcu_boot_entry); + sp = list_first_entry(&srcu_boot_list, struct srcu_struct, + work.work.entry); check_init_srcu_struct(sp); - list_del_init(&sp->srcu_boot_entry); + list_del_init(&sp->work.work.entry); queue_work(rcu_gp_wq, &sp->work.work); } }