Issues reported during the suspend-to-disk process lead Linux creator Linus Torvalds to suggest, "please - just make the f*cking suspend-to-disk use other routines already. 99% of all hardware needs to do exactly *nothing* on suspend-to-disk, and the ones that really do need things tend to need to not do a whole lot." He went on to explain why sharing the code path for suspend-to-disk and freezing to RAM is wrong:
"For example, the 'freeze' action for USB (which is one of the hardest things to suspend) should literally be something like just setting the controller STOP bit, and waiting for it to have stopped. The 'unfreeze' should be to just clear the stop bit, while the 'restart' should be just a controller reset to use the current memory image. NONE OF THIS HAS ABSOLUTELY ANYTHING TO DO WITH SUSPEND. It never did. I've told people so for years. Maybe actually seeing the problems will make people realize."
Linus also noted another advantage to having separate code paths for the two actions, "the other issue is that I've long wanted to make sure that when people fix suspend-to-ram, they don't screw up suspend-to-disk by mistake and vice versa." During the discussion, Rafael Wysocki noted that he would be fixing this up presently, "I'm already convinced, really. :-)"
What started as the review of a bug report grew into an interesting debate as Linus Torvalds slammed the current suspend and resume [story] design in the Linux Kernel, "why the HELL cannot you realize that kernel threads are different? The right thing to do is AND HAS ALWAYS BEEN, to stop and start user threads only around the whole thing. Don't touch those kernel threads. Stop freezing them." Later in the discussion, Linus noted that he had no interest in Suspend to Disk (STD), and was only interested in a working Suspend to Ram (STR) implementation. He noted that complexity introduced by STD was infecting the STR logic, and that the two should be completely separated, "what irritates me is that STR really shouldn't have _had_ that bug at all. The only reason STR had the same bug as STD was exactly the fact that the two features are too closely inter-twined in the kernel. That irritates me hugely. We had a bug we should never had had! We had a bug because people are sharing code that shouldn't be shared! We had a bug because of code that makes no sense in the first place!" Linus noted that he doesn't use laptops much, but still likes STR on his desktop, "STR means they are quiet and don't waste energy when I don't use them, but they're instantly available when I care." He then went on to point to design flaws in the freezer:
"I actually don't think that processes should be frozen really at all. I agree that filesystems have to be frozen (and I think that checkpointing of the filesystem or block device is 'too clever'), but I just don't think that has anything to do with freezing processes. So I'd actually much prefer to freeze at the VFS (and socket layers, etc), and make sure that anybody who tries to write or do something else that we cannot do until resuming, will just be blocked (or perhaps just buffered)!"