lkml.org 
[lkml]   [2015]   [Nov]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.2 102/110] sched/deadline: Fix migration of SCHED_DEADLINE tasks
    Date
    4.2-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Luca Abeni <luca.abeni@unitn.it>

    commit 5aa5050787f449e7eaef2c5ec93c7b357aa7dcdc upstream.

    Commit:

    9d5142624256 ("sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target")

    broke select_task_rq_dl() and find_lock_later_rq(), because it introduced
    a comparison between the local task's deadline and dl.earliest_dl.curr of
    the remote queue.

    However, if the remote runqueue does not contain any SCHED_DEADLINE
    task its earliest_dl.curr is 0 (always smaller than the deadline of
    the local task) and the remote runqueue is not selected for pushing.

    As a result, if an application creates multiple SCHED_DEADLINE
    threads, they will never be pushed to runqueues that do not already
    contain SCHED_DEADLINE tasks.

    This patch fixes the issue by checking if dl.dl_nr_running == 0.

    Signed-off-by: Luca Abeni <luca.abeni@unitn.it>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Juri Lelli <juri.lelli@arm.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Wanpeng Li <wanpeng.li@linux.intel.com>
    Fixes: 9d5142624256 ("sched/deadline: Reduce rq lock contention by eliminating locking of non-feasible target")
    Link: http://lkml.kernel.org/r/1444982781-15608-1-git-send-email-luca.abeni@unitn.it
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/sched/deadline.c | 8 +++++---
    1 file changed, 5 insertions(+), 3 deletions(-)

    --- a/kernel/sched/deadline.c
    +++ b/kernel/sched/deadline.c
    @@ -1066,8 +1066,9 @@ select_task_rq_dl(struct task_struct *p,
    int target = find_later_rq(p);

    if (target != -1 &&
    - dl_time_before(p->dl.deadline,
    - cpu_rq(target)->dl.earliest_dl.curr))
    + (dl_time_before(p->dl.deadline,
    + cpu_rq(target)->dl.earliest_dl.curr) ||
    + (cpu_rq(target)->dl.dl_nr_running == 0)))
    cpu = target;
    }
    rcu_read_unlock();
    @@ -1417,7 +1418,8 @@ static struct rq *find_lock_later_rq(str

    later_rq = cpu_rq(cpu);

    - if (!dl_time_before(task->dl.deadline,
    + if (later_rq->dl.dl_nr_running &&
    + !dl_time_before(task->dl.deadline,
    later_rq->dl.earliest_dl.curr)) {
    /*
    * Target rq has tasks of equal or earlier deadline,



    \
     
     \ /
      Last update: 2015-11-06 21:01    [W:5.205 / U:0.440 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site