Re: [PATCH v5 0/2] printk: Console owner and waiter logic cleanup

[Sergey Senozhatsky]

On (01/22/18 17:56), Sergey Senozhatsky wrote:
[..]
> Assume the following,

But more importantly we are missing another huge thing - console_unlock().

Suppose:

	console_lock();
	<< preemption >>
						printk
						printk
						..
						printk
	console_unlock()
	 for (;;) {
		call_console_drivers()
		   dump_stack
		   queue IRQ work

		IRQ work >>
		   flush_printk_safe
		   printk_deferred()
		   ...
		   printk_deferred()
		<< iret
	 }

This should explode: sleepable console_unlock() may reschedule,
printk_safe flush bypasses recursion checks.

	-ss