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    SubjectRe: [PATCH 02/27] smpboot: Add provisions for arch-specific locking around cpu_online_mask
    Adding arch maintainers to Cc, which I had missed earlier. No changes to the 
    patch.

    ======

    From: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    Subject: [PATCH 02/27] smpboot: Add provisions for arch-specific locking around cpu_online_mask

    We want to make smp booting as generic as possible and remove code
    duplication in arch/ directories.

    While manipulating the cpu_online_mask, x86 uses an additional lock, i.e.,
    'vector_lock'. So provide a generic way to implement such arch-specific
    extra locking, by providing weakly defined functions arch_vector_lock()
    and arch_vector_unlock() which can be overriden by different architectures
    suitably.

    Cc: Thomas Gleixner <tglx@linutronix.de>
    Cc: Suresh Siddha <suresh.b.siddha@intel.com>
    Cc: Venkatesh Pallipadi <venki@google.com>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: Ralf Baechle <ralf@linux-mips.org>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Paul Mundt <lethal@linux-sh.org>
    Cc: Chris Metcalf <cmetcalf@tilera.com>
    Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: Mike Frysinger <vapier@gentoo.org>
    Cc: Hirokazu Takata <takata@linux-m32r.org>
    Cc: Richard Kuo <rkuo@codeaurora.org>
    Cc: David Howells <dhowells@redhat.com>
    Cc: Bob Liu <lliubbo@gmail.com>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: Richard Weinberger <richard@nod.at>
    Cc: Jesper Nilsson <jesper.nilsson@axis.com>
    Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
    Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
    Cc: Russell King <linux@arm.linux.org.uk>
    Cc: Matt Turner <mattst88@gmail.com>
    Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
    ---

    kernel/smpboot.c | 11 ++++++++++-
    1 files changed, 10 insertions(+), 1 deletions(-)

    diff --git a/kernel/smpboot.c b/kernel/smpboot.c
    index 6c26133..5ae1805 100644
    --- a/kernel/smpboot.c
    +++ b/kernel/smpboot.c
    @@ -107,6 +107,13 @@ void __weak __cpu_pre_online(void *arg) {}
    void __weak __cpu_post_online(void *arg) {}
    #endif

    +/*
    + * Optional arch-specific locking for manipulating cpu_online_mask while
    + * bringing up secondary CPUs.
    + */
    +void __weak arch_vector_lock(void) {}
    +void __weak arch_vector_unlock(void) {}
    +

    /**
    * smpboot_start_secondary - Generic way to boot secondary processors
    @@ -129,8 +136,10 @@ void __cpuinit smpboot_start_secondary(void *arg)

    __cpu_pre_online(arg);

    - /* Set the CPU in the cpu_online_mask */
    + /* Set the CPU in the cpu_online_mask with required locks held */
    + arch_vector_lock();
    set_cpu_online(cpu, true);
    + arch_vector_unlock();

    __cpu_post_online(arg);




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