From: Hugh Dickins <hughd@xxxxxxxxxx> Date: Thu, 26 Aug 2010 03:54:28 -0700 > On Wed, Aug 25, 2010 at 11:41 PM, David Miller <davem@xxxxxxxxxxxxx> wrote: >> From: Hugh Dickins <hughd@xxxxxxxxxx> >> Date: Wed, 25 Aug 2010 23:12:54 -0700 (PDT) >> >>> After several hours, kbuild tests hang with anon_vma_prepare() spinning on >>> a newly allocated anon_vma's lock - on a box with CONFIG_TREE_PREEMPT_RCU=y >>> (which makes this very much more likely, but it could happen without). >>> >>> The ever-subtle page_lock_anon_vma() now needs a further twist: since >>> anon_vma_prepare() and anon_vma_fork() are liable to change the ->root >>> of a reused anon_vma structure at any moment, page_lock_anon_vma() >>> needs to check page_mapped() again before succeeding, otherwise >>> page_unlock_anon_vma() might address a different root->lock. >>> >>> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx> >> >> Interesting, is the condition which allows this to trigger specific >> to this merge window or was it always possible? > > Just specific to this merge window, which started using > anon_vma->root->lock in place of anon_vma->lock (anon_vma->root is > often anon_vma itself, but not always). Ok, because I've been seeing mysterious hangs recently on one of my sparc64 boxes and I was wondering if this might explain them :-) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>