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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-08-15 03:01:53 +0400
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-09-08 03:27:34 +0400
commit1d082fd061884a587c490c4fc8a2056ce1e47624 (patch)
treea8f715a674a036b1b7500a16ea11381d40659e42 /include/linux/init_task.h
parent4ff475ed4cf61a7f56bbfbc424147189d0022b38 (diff)
downloadlinux-1d082fd061884a587c490c4fc8a2056ce1e47624.tar.xz
rcu: Remove local_irq_disable() in rcu_preempt_note_context_switch()
The rcu_preempt_note_context_switch() function is on a scheduling fast path, so it would be good to avoid disabling irqs. The reason that irqs are disabled is to synchronize process-level and irq-handler access to the task_struct ->rcu_read_unlock_special bitmask. This commit therefore makes ->rcu_read_unlock_special instead be a union of bools with a short allowing single-access checks in RCU's __rcu_read_unlock(). This results in the process-level and irq-handler accesses being simple loads and stores, so that irqs need no longer be disabled. This commit therefore removes the irq disabling from rcu_preempt_note_context_switch(). Reported-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'include/linux/init_task.h')
-rw-r--r--include/linux/init_task.h2
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 03b274873b06..77fc43f8fb72 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -111,7 +111,7 @@ extern struct group_info init_groups;
#ifdef CONFIG_PREEMPT_RCU
#define INIT_TASK_RCU_PREEMPT(tsk) \
.rcu_read_lock_nesting = 0, \
- .rcu_read_unlock_special = 0, \
+ .rcu_read_unlock_special.s = 0, \
.rcu_node_entry = LIST_HEAD_INIT(tsk.rcu_node_entry), \
INIT_TASK_RCU_TREE_PREEMPT()
#else