On 12-07-16, 15:56, Petr Mladek wrote:

Ah, I have missed that the hang happens only when you use the async
printk patchset.

And that also doesn't happen always, but only sometimes. So there is a
race somewhere I feel :)

I wonder if it is somehow related to the commit 8d91f8b15361dfb438ab
("printk: do cond_resched() between lines while outputting to
consoles"). A process (printk thread) might sleep with taken
console_sem. Then suspend_console() might be unable to
get the semaphore in console_lock() and might deadlock.

I am not sure at this point really, and I don't have indepth knowledge
of printk core as well (I should accept that here :).

Does it help to enable "no_console_suspend" please?

No. With no_console_suspend, we just print one more line (Disabling
non-boot CPUs) and once the interrupt on the local CPU are disabled,
we don't get any more prints until a resume happens.

-- 
viresh