diff options
| author | Paul E. McKenney <paul.mckenney@linaro.org> | 2012-01-11 17:25:17 -0800 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2012-02-21 09:03:43 -0800 |
| commit | 1aa03f1188f7b0b85df2de602b33ee7b6fab8e00 (patch) | |
| tree | 20ee8fc1aa5bccc8d8cf53c705d9cc766058eaf5 | |
| parent | 8762705ad4ac860bb78434409df463d02ac8f027 (diff) | |
rcu: Simplify unboosting checks
This is a port of commit #82e78d80 from TREE_PREEMPT_RCU to
TINY_PREEMPT_RCU.
This commit uses the fact that current->rcu_boost_mutex is set
any time that the RCU_READ_UNLOCK_BOOSTED flag is set in the
current->rcu_read_unlock_special bitmask. This allows tests of
the bit to be changed to tests of the pointer, which in turn allows
the RCU_READ_UNLOCK_BOOSTED flag to be eliminated.
Please note that the check of current->rcu_read_unlock_special need not
change because any time that RCU_READ_UNLOCK_BOOSTED was set, so was
RCU_READ_UNLOCK_BLOCKED. Therefore, __rcu_read_unlock() can continue
testing current->rcu_read_unlock_special for non-zero, as before.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| -rw-r--r-- | include/linux/sched.h | 3 | ||||
| -rw-r--r-- | kernel/rcutiny_plugin.h | 10 |
2 files changed, 7 insertions, 6 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 7d379a6bfd8..e692abaf915 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1864,8 +1864,7 @@ extern void task_clear_jobctl_pending(struct task_struct *task, #ifdef CONFIG_PREEMPT_RCU #define RCU_READ_UNLOCK_BLOCKED (1 << 0) /* blocked while in RCU read-side. */ -#define RCU_READ_UNLOCK_BOOSTED (1 << 1) /* boosted while in RCU read-side. */ -#define RCU_READ_UNLOCK_NEED_QS (1 << 2) /* RCU core needs CPU response. */ +#define RCU_READ_UNLOCK_NEED_QS (1 << 1) /* RCU core needs CPU response. */ static inline void rcu_copy_process(struct task_struct *p) { diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index 387c2759e1b..22ecea0dfb6 100644 --- a/kernel/rcutiny_plugin.h +++ b/kernel/rcutiny_plugin.h @@ -318,7 +318,6 @@ static int rcu_boost(void) t = container_of(tb, struct task_struct, rcu_node_entry); 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); /* Keep lockdep happy. */ @@ -550,6 +549,9 @@ static noinline void rcu_read_unlock_special(struct task_struct *t) int empty_exp; unsigned long flags; struct list_head *np; +#ifdef CONFIG_RCU_BOOST + struct rt_mutex *rbmp = NULL; +#endif /* #ifdef CONFIG_RCU_BOOST */ int special; /* @@ -615,10 +617,10 @@ static noinline void rcu_read_unlock_special(struct task_struct *t) } #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); + if (t->rcu_boost_mutex != NULL) { + rbmp = t->rcu_boost_mutex; t->rcu_boost_mutex = NULL; + rt_mutex_unlock(rbmp); } #endif /* #ifdef CONFIG_RCU_BOOST */ local_irq_restore(flags); |