linux-next

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History

Frederic Weisbecker 3882ec6439 nohz: Use IPI implicit full barrier against rq->nr_running r/w

A full dynticks CPU is allowed to stop its tick when a single task runs.
Meanwhile when a new task gets enqueued, the CPU must be notified so that
it can restart its tick to maintain local fairness and other accounting
details.

This notification is performed by way of an IPI. Then when the target
receives the IPI, we expect it to see the new value of rq->nr_running.

Hence the following ordering scenario:

   CPU 0                   CPU 1

   write rq->running       get IPI
   smp_wmb()               smp_rmb()
   send IPI                read rq->nr_running

But Paul Mckenney says that nowadays IPIs imply a full barrier on
all architectures. So we can safely remove this pair and rely on the
implicit barriers that come along IPI send/receive. Lets
just comment on this new assumption.

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>

2014-06-16 16:27:24 +02:00

auto_group.c

sched: Replace hardcoding of -20 and 19 with MIN_NICE and MAX_NICE

2014-02-22 18:15:54 +01:00

auto_group.h

Revert "sched/autogroup: Fix crash on reboot when autogroup is disabled"

2012-12-11 10:23:45 +01:00

clock.c

kernel: use macros from compiler.h instead of __attribute__((...))

2014-04-07 16:36:11 -07:00

completion.c

sched: Move completion code from core.c to completion.c