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

Sergey Senozhatsky
2018-01-22T10:29:04Z

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