Re: SCSI RAM driver ported to 3.3 kernel for file system and I/O testing

[Matthew Wilcox <willy@linux.intel.com>]

On Wed, May 16, 2012 at 03:54:06PM -0400, chetan loke wrote:
> I thought that 'scsi_ram_device_thread' has a
> 'wait_event_interruptible' call if it sees that the list is empty. I
> don't see that call that's why the confusion. Either queuecmd or
> kthread will get the lock and so why keep the kthread spinning in that
> while loop if there's nothing to do?

It doesn't spin, it sleeps:

+               spin_lock_irqsave(host->host_lock, flags);
+               if (list_empty(&ram_device->commands)) {
+                       set_current_state(TASK_INTERRUPTIBLE);
+                       spin_unlock_irqrestore(host->host_lock, flags);
+                       schedule();
+                       continue;
+               }