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SubjectRe: [PATCH printk 3/5] printk: use buffer pool for sprint buffers
On (20/09/22 17:44), John Ogness wrote:
> +/*
> + * The sprint buffers are used with interrupts disabled, so each CPU
> + * only requires 2 buffers: for non-NMI and NMI contexts. Recursive
> + * printk() calls are handled by the safe buffers.
> + */
> +#define SPRINT_CTX_DEPTH 2
> +
> +/* Static sprint buffers for early boot (only 1 CPU). */
> +static DECLARE_BITMAP(sprint_static_textbuf_map, SPRINT_CTX_DEPTH);
> +static char sprint_static_textbuf[SPRINT_CTX_DEPTH * LOG_LINE_MAX];
> +
> +/* Dynamically allocated sprint buffers. */
> +static unsigned int sprint_dynamic_textbuf_count;
> +static unsigned long *sprint_dynamic_textbuf_map;
> +static char *sprint_dynamic_textbuf;

Just a question:

Can dynamic_textbuf be a PER_CPU array of five textbuf[1024] buffers
(for normal printk, nmi, hard irq, soft irq and one extra buffer for
recursive printk calls)?

So then we'd

vprintk(...)
{
preempt_disable();
buf = this_cpu_ptr(... preempt_count_to_ctx());
...
preempt_enable();
}

preempt_disable()/preempt_enable() is already in printk().

-ss

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