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    SubjectRe: Regression: turbostat stops working after suspend/resume cycle\
    On Sun, May 17, 2015 at 05:48:44PM +0200, Gabriele Mazzotta wrote:
    > Hi,
    >
    > I've recently noticed that if I suspend and resume my laptop, I can no
    > longer execute turbostat. This is what I get when I try to start it:
    > # turbostat
    > Could not migrate to CPU 1
    > turbostat: re-initialized with num_cpus 4
    > Could not migrate to CPU 1
    >
    > Since everything works as expected with v4.0, I ran a bisection and
    > found that commit 3c18d447b3b36a8d ("sched/core: Check for available
    > DL bandwidth in cpuset_cpu_inactive()") is the cause of the regression.
    >
    > I don't know if there's something else affected by that change, but
    > I can consistently reproduce the bug with turbostat.


    This should be fixed by the below commit which is already in Linus'
    tree.

    ---
    commit 533445c6e53368569e50ab3fb712230c03d523f3
    Author: Omar Sandoval <osandov@osandov.com>
    Date: Mon May 4 03:09:36 2015 -0700

    sched/core: Fix regression in cpuset_cpu_inactive() for suspend

    Commit 3c18d447b3b3 ("sched/core: Check for available DL bandwidth in
    cpuset_cpu_inactive()"), a SCHED_DEADLINE bugfix, had a logic error that
    caused a regression in setting a CPU inactive during suspend. I ran into
    this when a program was failing pthread_setaffinity_np() with EINVAL after
    a suspend+wake up.

    A simple reproducer:

    $ ./a.out
    sched_setaffinity: Success
    $ systemctl suspend
    $ ./a.out
    sched_setaffinity: Invalid argument

    ... where ./a.out is:

    #define _GNU_SOURCE
    #include <errno.h>
    #include <sched.h>
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <unistd.h>

    int main(void)
    {
    long num_cores;
    cpu_set_t cpu_set;
    int ret;

    num_cores = sysconf(_SC_NPROCESSORS_ONLN);
    CPU_ZERO(&cpu_set);
    CPU_SET(num_cores - 1, &cpu_set);
    errno = 0;
    ret = sched_setaffinity(getpid(), sizeof(cpu_set), &cpu_set);
    perror("sched_setaffinity");
    return ret ? EXIT_FAILURE : EXIT_SUCCESS;
    }

    The mistake is that suspend is handled in the action ==
    CPU_DOWN_PREPARE_FROZEN case of the switch statement in
    cpuset_cpu_inactive().

    However, the commit in question masked out CPU_TASKS_FROZEN
    from the action, making this case dead.

    The fix is straightforward.

    Signed-off-by: Omar Sandoval <osandov@osandov.com>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Juri Lelli <juri.lelli@arm.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Fixes: 3c18d447b3b3 ("sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()")
    Link: http://lkml.kernel.org/r/1cb5ecb3d6543c38cce5790387f336f54ec8e2bc.1430733960.git.osandov@osandov.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>

    diff --git a/kernel/sched/core.c b/kernel/sched/core.c
    index 34db9bf892a3..57bd333bc4ab 100644
    --- a/kernel/sched/core.c
    +++ b/kernel/sched/core.c
    @@ -6999,27 +6999,23 @@ static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
    unsigned long flags;
    long cpu = (long)hcpu;
    struct dl_bw *dl_b;
    + bool overflow;
    + int cpus;

    - switch (action & ~CPU_TASKS_FROZEN) {
    + switch (action) {
    case CPU_DOWN_PREPARE:
    - /* explicitly allow suspend */
    - if (!(action & CPU_TASKS_FROZEN)) {
    - bool overflow;
    - int cpus;
    -
    - rcu_read_lock_sched();
    - dl_b = dl_bw_of(cpu);
    + rcu_read_lock_sched();
    + dl_b = dl_bw_of(cpu);

    - raw_spin_lock_irqsave(&dl_b->lock, flags);
    - cpus = dl_bw_cpus(cpu);
    - overflow = __dl_overflow(dl_b, cpus, 0, 0);
    - raw_spin_unlock_irqrestore(&dl_b->lock, flags);
    + raw_spin_lock_irqsave(&dl_b->lock, flags);
    + cpus = dl_bw_cpus(cpu);
    + overflow = __dl_overflow(dl_b, cpus, 0, 0);
    + raw_spin_unlock_irqrestore(&dl_b->lock, flags);

    - rcu_read_unlock_sched();
    + rcu_read_unlock_sched();

    - if (overflow)
    - return notifier_from_errno(-EBUSY);
    - }
    + if (overflow)
    + return notifier_from_errno(-EBUSY);
    cpuset_update_active_cpus(false);
    break;
    case CPU_DOWN_PREPARE_FROZEN:

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