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    Subject[PATCH 21/41] nohz/cpuset: Flush cputime on threads in nohz cpusets when waiting leader
    Date
    When we wait for a zombie task, flush the cputimes on nohz cpusets
    in case we are waiting for a group leader that has threads running
    in nohz CPUs. This way thread_group_times() doesn't report stale
    values.

    <doubts>
    If I understood well the code, by the time we call that thread_group_times(),
    we may have childs that are still running, so this is necessary.
    But I need to check deeper.
    </doubts>

    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Alessio Igor Bogani <abogani@kernel.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Avi Kivity <avi@redhat.com>
    Cc: Chris Metcalf <cmetcalf@tilera.com>
    Cc: Christoph Lameter <cl@linux.com>
    Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
    Cc: Geoff Levand <geoff@infradead.org>
    Cc: Gilad Ben Yossef <gilad@benyossef.com>
    Cc: Hakan Akkan <hakanakkan@gmail.com>
    Cc: Ingo Molnar <mingo@kernel.org>
    Cc: Kevin Hilman <khilman@ti.com>
    Cc: Max Krasnyansky <maxk@qualcomm.com>
    Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Stephen Hemminger <shemminger@vyatta.com>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    ---
    kernel/exit.c | 8 ++++++++
    1 files changed, 8 insertions(+), 0 deletions(-)

    diff --git a/kernel/exit.c b/kernel/exit.c
    index 4b4042f..c194662 100644
    --- a/kernel/exit.c
    +++ b/kernel/exit.c
    @@ -52,6 +52,7 @@
    #include <linux/hw_breakpoint.h>
    #include <linux/oom.h>
    #include <linux/writeback.h>
    +#include <linux/cpuset.h>

    #include <asm/uaccess.h>
    #include <asm/unistd.h>
    @@ -1712,6 +1713,13 @@ repeat:
    (!wo->wo_pid || hlist_empty(&wo->wo_pid->tasks[wo->wo_type])))
    goto notask;

    + /*
    + * For cputime in sub-threads before adding them.
    + * Must be called outside tasklist_lock lock because write lock
    + * can be acquired under irqs disabled.
    + */
    + cpuset_nohz_flush_cputimes();
    +
    set_current_state(TASK_INTERRUPTIBLE);
    read_lock(&tasklist_lock);
    tsk = current;
    --
    1.7.5.4


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