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    SubjectRe: [PATCH 3.19-rc2 v13 4/5] ARM: Add support for on-demand backtrace of other CPUs
    On Mon, Jan 05, 2015 at 10:19:25AM -0500, Steven Rostedt wrote:
    > On Mon, 5 Jan 2015 14:54:58 +0000
    > Daniel Thompson <daniel.thompson@linaro.org> wrote:
    > > +/* For reliability, we're prepared to waste bits here. */
    > > +static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
    > > +static cpumask_t printtrace_mask;
    > > +
    > > +#define NMI_BUF_SIZE 4096
    > > +
    > > +struct nmi_seq_buf {
    > > + unsigned char buffer[NMI_BUF_SIZE];
    > > + struct seq_buf seq;
    > > +};

    Am I missing something or does this limit us to 4096 characters of
    backtrace output per CPU?

    > This is the same code as in x86. I wonder if we should move the
    > duplicate code into kernel/printk/ and have it compiled if the arch
    > requests it (CONFIG_ARCH_WANT_NMI_PRINTK or something). That way we
    > don't have 20 copies of the same nmi_vprintk() and later find that we
    > need to change it, and have to change it in 20 different archs.

    Agreed, though I wonder about the buffer size.

    --
    FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
    according to speedtest.net.


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