On (01/16/17 22:26), Sergey Senozhatsky wrote:

On (01/16/17 13:48), Petr Mladek wrote:
[..]

quoted

The async printk code looks like this:

vprintk_emit(...)
{


		if (can_printk_async()) {
			/* Offload printing to a schedulable context. */
			printk_kthread_need_flush_console = true;
			wake_up_process(printk_kthread);
		} else {
			/*
			 * Try to acquire and then immediately release the
			 * console semaphore.  The release will print out
			 * buffers and wake up /dev/kmsg and syslog() users.
			 */
			if (console_trylock())
				console_unlock();
		}

So, there is still the console_trylock() for the sync mode. Or do I
see an outdated variant?

no, it doesn't.

I meant that none of this is happening in vprintk_emit(). there is no
console_sem in vprintk_emit() at all. eveything is done in deferred printk.

	-ss