tree ac3a8b6ac0278f77fbfbac5de2f2b2caf3f31851
parent 1060157a3daf1530b8562e93e94950feb4eb00c9
author Frederic Weisbecker <fweisbec@gmail.com> 1400861421 +0200
committer Steven Rostedt <rostedt@goodmis.org> 1435859781 -0400

irq_work: Split raised and lazy lists

commit b93e0b8fa819c3d5641794ed9a07e643416aa0fd upstream.

An irq work can be handled from two places: from the tick if the work
carries the "lazy" flag and the tick is periodic, or from a self IPI.

We merge all these works in a single list and we use some per cpu latch
to avoid raising a self-IPI when one is already pending.

Now we could do away with this ugly latch if only the list was only made of
non-lazy works. Just enqueueing a work on the empty list would be enough
to know if we need to raise an IPI or not.

Also we are going to implement remote irq work queuing. Then the per CPU
latch will need to become atomic in the global scope. That's too bad
because, here as well, just enqueueing a work on an empty list of
non-lazy works would be enough to know if we need to raise an IPI or not.

So lets take a way out of this: split the works in two distinct lists,
one for the works that can be handled by the next tick and another
one for those handled by the IPI. Just checking if the latter is empty
when we queue a new work is enough to know if we need to raise an IPI.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

Conflicts:
	kernel/irq_work.c

Merged in some changes from 4.0-rt that added the irq_work_tick()
code, and also has the raised_list called from hardirq context and
the lazy_list always from softirq context (which is threaded on RT)

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>