Re: [patch] take 2 Re: PG_swap_entry bug in recent kernels

[kanoj@google.engr.sgi.com (Kanoj Sarcar)]

> 
> I was talking about the locking order issue you raised about the necessary
> vmlist_*_lock I added in swapoff.
> 
> What I meant is that in 2.2.x there was no need of the
> vmlist_*_lock/page_cache_lock in swapoff because we was relying on the big
> kernel lock while playing with pagetables and vmas (same in swap_out()).
> 
> In 2.3.x both swap_out and swapoff needs to grab first the tasklist_lock
> (as in 2.2.x) and then the vmlist_*_lock (otherwise as first the vma
> browsing may happen during a vma list modification).
> 
> Andrea
> 


As I mentioned before, have you stress tested this to make sure grabbing
read_lock(tasklist_lock), then spin_lock(vmlist_lock) is not deadlock
prone? I _think_ you will run into problems ... and we can then stop 
discussing this. 

Kanoj
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