+
+Q: Kernel thread must voluntarily freeze itself (call 'refrigerator'). But
+I found some kernel threads don't do it, and they don't freeze, and
+so the system can't sleep. Is this a known behavior?
+
+A: All such kernel threads need to be fixed, one by one. Select place
+where it is safe to be frozen (no kernel semaphores should be held at
+that point and it must be safe to sleep there), and add:
+
+ if (current->flags & PF_FREEZE)
+ refrigerator(PF_FREEZE);
+
+Q: What is the difference between between "platform", "shutdown" and
+"firmware" in /sys/power/disk?
+
+A:
+
+shutdown: save state in linux, then tell bios to powerdown
+
+platform: save state in linux, then tell bios to powerdown and blink
+ "suspended led"
+
+firmware: tell bios to save state itself [needs BIOS-specific suspend
+ partition, and has very little to do with swsusp]
+
+"platform" is actually right thing to do, but "shutdown" is most
+reliable.