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rcu: Simplify priority boosting by putting rt_mutex in rcu_node

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RCU priority boosting currently checks for boosting via a pointer in
task_struct.  However, this is not needed: As Oleg noted, if the
rt_mutex is placed in the rcu_node instead of on the booster's stack,
the boostee can simply check it see if it owns the lock.  This commit
makes this change, shrinking task_struct by one pointer and the kernel
by thirteen lines.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney
2014-06-12 13:30:25 -07:00
parent 48bd8e9b82
commit abaa93d9e1
4 changed files with 15 additions and 28 deletions
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9
include/linux/init_task.h
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@@ -102,12 +102,6 @@ extern struct group_info init_groups;
#define INIT_IDS
#endif
#ifdef CONFIG_RCU_BOOST
#define INIT_TASK_RCU_BOOST() \
.rcu_boost_mutex = NULL,
#else
#define INIT_TASK_RCU_BOOST()
#endif
#ifdef CONFIG_TREE_PREEMPT_RCU
#define INIT_TASK_RCU_TREE_PREEMPT() \
.rcu_blocked_node = NULL,
@@ -119,8 +113,7 @@ extern struct group_info init_groups;
.rcu_read_lock_nesting = 0, \
.rcu_read_unlock_special = 0, \
.rcu_node_entry = LIST_HEAD_INIT(tsk.rcu_node_entry), \
INIT_TASK_RCU_TREE_PREEMPT() \
INIT_TASK_RCU_BOOST()
INIT_TASK_RCU_TREE_PREEMPT()
#else
#define INIT_TASK_RCU_PREEMPT(tsk)
#endif