Messages in this thread | | | Date | Mon, 4 Mar 2019 18:24:44 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [RFC PATCH v1 15/25] printk: print history for new consoles |
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On (02/26/19 16:22), John Ogness wrote: > > This looks like an alien. The code is supposed to write one message > > from the given buffer. And some huge job is well hidden there. > > This is a very simple implementation of a printk kthread. It probably > makes more sense to have a printk kthread per console. That would allow > fast consoles to not be penalized by slow consoles. Due to the > per-console seq tracking, the code would already support it.
I believe we discussed "polling consoles" several times.
printk-kthread is one way to implement polling. Another one might already be implemented in, probably, all serial drivers and we just need to extend it a bit - polling from console's IRQ handler.
Serial drivers poll UART xmit buffer and print (usually) up to `count' bytes:
static irqreturn_t foo_irq_handler(int irq, void *id) { int count = 512;
[...] while (count > 0 && !uart_circ_empty(xmit)) { wr_regb(port, TX, xmit->buf[xmit->tail]); xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1); count--; } [...]
return IRQ_HANDLED; }
So we can also grub NUM (e.g. max 64 entries) pending logbuf messages and print them from device's isr.
-ss
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