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srcu: Make early-boot call_srcu() reuse workqueue lists

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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 <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Paul E. McKenney 2018-08-14 14:41:49 -07:00
parent 55cda2290b
commit 4e6ea4ef56
4 changed files with 11 additions and 15 deletions
Download patch file Download diff file Expand all files Collapse all files

2
include/linux/srcutiny.h
View file

@ -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) \
}

3
include/linux/srcutree.h
View file

@ -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) \
}