On Wed, 9 Jan 2013 17:32:26 +0800 Tang Chen <tangchen@xxxxxxxxxxxxxx> wrote: > We remove the memory like this: > 1. lock memory hotplug > 2. offline a memory block > 3. unlock memory hotplug > 4. repeat 1-3 to offline all memory blocks > 5. lock memory hotplug > 6. remove memory(TODO) > 7. unlock memory hotplug > > All memory blocks must be offlined before removing memory. But we don't hold > the lock in the whole operation. So we should check whether all memory blocks > are offlined before step6. Otherwise, kernel maybe panicked. Well, the obvious question is: why don't we hold lock_memory_hotplug() for all of steps 1-4? Please send the reasons for this in a form which I can paste into the changelog. Actually, I wonder if doing this would fix a race in the current remove_memory() repeat: loop. That code does a find_memory_block_hinted() followed by offline_memory_block(), but afaict find_memory_block_hinted() only does a get_device(). Is the get_device() sufficiently strong to prevent problems if another thread concurrently offlines or otherwise alters this memory_block's state? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>