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| 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 /kernel/rcutiny_plugin.h | |
| parent | 8762705ad4ac860bb78434409df463d02ac8f027 (diff) | |
| download | lwn-1aa03f1188f7b0b85df2de602b33ee7b6fab8e00.tar.gz lwn-1aa03f1188f7b0b85df2de602b33ee7b6fab8e00.zip | |
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>
Diffstat (limited to 'kernel/rcutiny_plugin.h')
| -rw-r--r-- | kernel/rcutiny_plugin.h | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h index 387c2759e1b0..22ecea0dfb62 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); |