lkml.org 
[lkml]   [2007]   [Jul]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] [19/58] x86_64: Don't use softirq save locks in smp_call_function
    On 7/19/07, Andi Kleen <ak@suse.de> wrote:
    >
    > It is not fully softirq safe anyways.

    Ack

    [ sorry, I remember having promised to send such a patch myself
    some time ago, but just forgot about it ... ]

    > Can't do a WARN_ON unfortunately because it could trigger in the
    > panic case.

    But this is not true at all. This function doesn't come anywhere
    on the panic codepath.

    > +++ linux/arch/x86_64/kernel/smp.c
    > @@ -386,9 +386,9 @@ int smp_call_function_single (int cpu, v
    > return 0;
    > }

    So I'd say we do need a:

    WARN_ON(irqs_disabled() || in_interrupt());

    or something right about here ...

    > - spin_lock_bh(&call_lock);
    > + spin_lock(&call_lock);
    > __smp_call_function_single(cpu, func, info, nonatomic, wait);
    > - spin_unlock_bh(&call_lock);
    > + spin_unlock(&call_lock);
    > put_cpu();
    > return 0;
    > }

    And oh, by the way, you can safely go ahead and put that warning
    in smp_call_function() *also*.

    Note that panic() -> smp_send_stop() -> calls into the lower-level
    __smp_call_function() directly.

    So neither smp_call_function() nor smp_call_function_single() come
    in the panic codepath -- the warnings there would be okay.

    Satyam
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-07-19 14:19    [W:4.157 / U:0.084 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site