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2014-04-10simple-wait: rename and export the equivalent of waitqueue_active()Paul Gortmaker
The function "swait_head_has_waiters()" was internalized into wait-simple.c but it parallels the waitqueue_active of normal waitqueue support. Given that there are over 150 waitqueue_active users in drivers/ fs/ kernel/ and the like, lets make it globally visible, and rename it to parallel the waitqueue_active accordingly. We'll need to do this if we expect to expand its usage beyond RT. Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-04-10wait-simple: Rework for use with completionsThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-04-10wait-simple: Simple waitqueue implementationThomas Gleixner
wait_queue is a swiss army knife and in most of the cases the complexity is not needed. For RT waitqueues are a constant source of trouble as we can't convert the head lock to a raw spinlock due to fancy and long lasting callbacks. Provide a slim version, which allows RT to replace wait queues. This should go mainline as well, as it lowers memory consumption and runtime overhead. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> smp_mb() added by Steven Rostedt to fix a race condition with swait wakeups vs adding items to the list.