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    Subject[tip:smp/hotplug] cpu/hotplug: Prevent alloc/free of irq descriptors during CPU up/down (again)
    Commit-ID:  aa877175e7a9982233ed8f10cb4bfddd78d82741
    Gitweb: http://git.kernel.org/tip/aa877175e7a9982233ed8f10cb4bfddd78d82741
    Author: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    AuthorDate: Wed, 3 Aug 2016 13:22:28 -0400
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitDate: Wed, 10 Aug 2016 15:42:57 +0200

    cpu/hotplug: Prevent alloc/free of irq descriptors during CPU up/down (again)

    Now that Xen no longer allocates irqs in _cpu_up() we can restore
    commit:

    a89941816726 ("hotplug: Prevent alloc/free of irq descriptors during cpu up/down")

    Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
    Reviewed-by: Juergen Gross <jgross@suse.com>
    Acked-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Cc: david.vrabel@citrix.com
    Cc: xen-devel@lists.xenproject.org
    Link: http://lkml.kernel.org/r/1470244948-17674-3-git-send-email-boris.ostrovsky@oracle.com
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/kernel/smpboot.c | 11 -----------
    kernel/cpu.c | 8 ++++++++
    2 files changed, 8 insertions(+), 11 deletions(-)

    diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
    index 2a6e84a..067de61 100644
    --- a/arch/x86/kernel/smpboot.c
    +++ b/arch/x86/kernel/smpboot.c
    @@ -1108,17 +1108,8 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)

    common_cpu_up(cpu, tidle);

    - /*
    - * We have to walk the irq descriptors to setup the vector
    - * space for the cpu which comes online. Prevent irq
    - * alloc/free across the bringup.
    - */
    - irq_lock_sparse();
    -
    err = do_boot_cpu(apicid, cpu, tidle);
    -
    if (err) {
    - irq_unlock_sparse();
    pr_err("do_boot_cpu failed(%d) to wakeup CPU#%u\n", err, cpu);
    return -EIO;
    }
    @@ -1136,8 +1127,6 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
    touch_nmi_watchdog();
    }

    - irq_unlock_sparse();
    -
    return 0;
    }

    diff --git a/kernel/cpu.c b/kernel/cpu.c
    index 341bf80..ec12b72 100644
    --- a/kernel/cpu.c
    +++ b/kernel/cpu.c
    @@ -349,8 +349,16 @@ static int bringup_cpu(unsigned int cpu)
    struct task_struct *idle = idle_thread_get(cpu);
    int ret;

    + /*
    + * Some architectures have to walk the irq descriptors to
    + * setup the vector space for the cpu which comes online.
    + * Prevent irq alloc/free across the bringup.
    + */
    + irq_lock_sparse();
    +
    /* Arch-specific enabling code. */
    ret = __cpu_up(cpu, idle);
    + irq_unlock_sparse();
    if (ret) {
    cpu_notify(CPU_UP_CANCELED, cpu);
    return ret;
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