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    Subject[tip:core/ipi] generic-ipi: eliminate spurious pointless WARN_ON()s
    Commit-ID:  6a09dfa870ba0ed21b1124539968a36b42660661
    Gitweb: http://git.kernel.org/tip/6a09dfa870ba0ed21b1124539968a36b42660661
    Author: Jan Beulich <jbeulich@novell.com>
    AuthorDate: Thu, 12 Mar 2009 13:21:50 +0000
    Commit: Ingo Molnar <mingo@elte.hu>
    CommitDate: Fri, 13 Mar 2009 02:14:41 +0100

    generic-ipi: eliminate spurious pointless WARN_ON()s

    Namely during early boot, the panic() or BUG() paths may end up in
    smp_call_function_*() with just a single online CPU. In that situation
    the warnings generated are not only meaningless, but also result in
    relevant output being cluttered.

    Therefore, defer the WARN_ON() checks until after the (unaffected from
    the problem that is being attempted to be detected here) cases have
    been handled.

    Signed-off-by: Jan Beulich <jbeulich@novell.com>
    LKML-Reference: <49B91A7E.76E4.0078.0@novell.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>


    ---
    kernel/smp.c | 12 ++++++------
    1 files changed, 6 insertions(+), 6 deletions(-)

    diff --git a/kernel/smp.c b/kernel/smp.c
    index 7ad2262..37b90a9 100644
    --- a/kernel/smp.c
    +++ b/kernel/smp.c
    @@ -284,9 +284,6 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
    */
    this_cpu = get_cpu();

    - /* Can deadlock when called with interrupts disabled */
    - WARN_ON(irqs_disabled());
    -
    if (cpu == this_cpu) {
    local_irq_save(flags);
    func(info);
    @@ -295,6 +292,9 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
    if ((unsigned)cpu < nr_cpu_ids && cpu_online(cpu)) {
    struct call_single_data *data = &d;

    + /* Can deadlock when called with interrupts disabled */
    + WARN_ON(irqs_disabled());
    +
    if (!wait)
    data = &__get_cpu_var(csd_data);

    @@ -364,9 +364,6 @@ void smp_call_function_many(const struct cpumask *mask,
    unsigned long flags;
    int cpu, next_cpu, this_cpu = smp_processor_id();

    - /* Can deadlock when called with interrupts disabled */
    - WARN_ON(irqs_disabled());
    -
    /* So, what's a CPU they want? Ignoring this one. */
    cpu = cpumask_first_and(mask, cpu_online_mask);
    if (cpu == this_cpu)
    @@ -387,6 +384,9 @@ void smp_call_function_many(const struct cpumask *mask,
    return;
    }

    + /* Can deadlock when called with interrupts disabled */
    + WARN_ON(irqs_disabled());
    +
    data = &__get_cpu_var(cfd_data);
    csd_lock(&data->csd);


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