Re: Documentation/vm/locking: why not hold two PT locks?
From: Robert Love <hidden>
Date: 2004-02-08 21:29:38
On Sun, 2004-02-08 at 16:18 -0500, Ed L Cashin wrote:
Hi. Documentation/vm/locking says one must not simultaneously hold the page table lock on mm A and mm B. Is that true? Where is the danger?
There isn't a proscribed lock ordering hierarchy, so you can deadlock. Assume thread 1 obtains the lock on mm A. Assume thread 2 obtains the lock on mm B. Assume thread 1 now obtains the lock on mm B - it is taken, so spin waiting. Assume thread 2 now obtains the lock on mm A - it too is taken, so spin waiting. Boom.. Robert Love -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"aart@kvack.org"> aart@kvack.org </a>