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SubjectRe: [PATCH] printk/nmi: Prevent deadlock when serializing NMI backtraces
On (05/18/18 11:07), Sergey Senozhatsky wrote:
>
> if (this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK) ||
> raw_spin_is_locked(&logbuf_lock)
>
> just to check per-CPU `printk_context' first and only afterwards
> access the global `logbuf_lock'. printk_nmi_enter() happens on
> every CPU, so maybe we can avoid some overhead by checking the
> local per-CPU data first.

Nah, may be it won't. This, probably, would have been the case if we
had continue to call console drivers from printk_safe section [at least].
CPUs don't spend that much time in printk_safe sections.

-ss

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