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    SubjectRe: [RFC][PATCH v6 1/2] printk: Make printk() completely async
    On Tue 2016-03-22 02:25:29, Sergey Senozhatsky wrote:
    > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
    > index e38579d..99c105d6 100644
    > --- a/kernel/printk/printk.c
    > +++ b/kernel/printk/printk.c
    > @@ -1619,12 +1721,21 @@ asmlinkage int vprintk_emit(int facility, int level,
    > int printed_len = 0;
    > int nmi_message_lost;
    > bool in_sched = false;
    > - /* cpu currently holding logbuf_lock in this function */
    > - static unsigned int logbuf_cpu = UINT_MAX;
    > + bool in_panic = console_loglevel == CONSOLE_LOGLEVEL_MOTORMOUTH;

    I am just looking at the printk in NMI patchset and I will need to
    deal with the panic state as well. I am not sure if this detection
    is secure.

    This console level is set also by kdb_show_stack()
    and kdb_dumpregs(). I am not sure how this kdb stuff works
    and if it affects normal kernel but...

    Anyway, it seems that many locations detects the panic situation
    via the variable oops_in_progress. It has another advantage
    that it can be easily checked and we would not need any extra
    variable here.


    > + bool sync_print = printk_sync;
    > +
    > + /* disable async printk */
    > + if (in_panic)
    > + printk_sync = true;

    In each case, we should not switch the global state if we
    only print debug traces.

    Best Regards,
    Petr

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