Re: [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