• Davidlohr Bueso's avatar
    sched/wait, RCU: Introduce rcuwait machinery · 8f95c90c
    Davidlohr Bueso authored
    rcuwait provides support for (single) RCU-safe task wait/wake functionality,
    with the caveat that it must not be called after exit_notify(), such that
    we avoid racing with rcu delayed_put_task_struct callbacks, task_struct
    being rcu unaware in this context -- for which we similarly have
    task_rcu_dereference() magic, but with different return semantics, which
    can conflict with the wakeup side.
    The interfaces are quite straightforward:
    More details are in the comments, but it's perhaps worth mentioning at least,
    that users must provide proper serialization when waiting on a condition, and
    avoid corrupting a concurrent waiter. Also care must be taken between the task
    and the condition for when calling the wakeup -- we cannot miss wakeups. When
    porting users, this is for example, a given when using waitqueues in that
    everything is done under the q->lock. As such, it can remove sources of non
    preemptable unbounded work for realtime.
    Signed-off-by: default avatarDavidlohr Bueso <dbueso@suse.de>
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Reviewed-by: default avatarOleg Nesterov <oleg@redhat.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: dave@stgolabs.net
    Link: http://lkml.kernel.org/r/1484148146-14210-2-git-send-email-dave@stgolabs.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
exit.c 44.2 KB