On 14-07-16, 09:55, Sergey Senozhatsky wrote:

excessive printing is just part of the problem here. if we cab cond_resched()
part of suspend/hibernation is cpu_down(), which lands in console_cpu_notify(),
that does synchronous printing for every CPU taken down:

static int console_cpu_notify(struct notifier_block *self,
	unsigned long action, void *hcpu)
{
	switch (action) {
	case CPU_ONLINE:
	case CPU_DEAD:
	case CPU_DOWN_FAILED:
	case CPU_UP_CANCELED:
		console_lock();
		console_unlock();
		^^^^^^^^^^^^^^
	}
	return NOTIFY_OK;
}

console_unlock() is synchronous (I posted a very early draft patch that makes
it asynchronous, but that's a future work). so if there is a ton of printk()-s,
then console_unlock() will print it, 100% guaranteed. even if printk_kthread
is doing the printing job at the moment, cpu down path will wait for it to
stop, lock the console semaphore, and got to console_unlock() printing loop.

Hmm...

in printk that you have posted, that will happen not only for CPU_DEAD,

It doesn't happen for CPU_DEAD right now as CONFIG_CONSOLE_FLUSH_ON_HOTPLUG
isn't enabled in my setup.

but for CPU_DYING as well (possibly, there is a /* invoked with preemption
disabled, so defer */ comment, so may be you never endup doing direct
printk there, but then you schedule a console_unlock() work).

-- 
viresh