On 08/18/2012 12:07 AM, Daniel Forrest wrote:
I was being careful since I wasn't certain about the locking. Does the test need to be protected by "lock_anon_vma_root"? That's why I chose the overhead of the possible wasted "anon_vma_chain_alloc".
The function anon_vma_clone is being called from fork(). When running fork(), the kernel holds the mm->mmap_sem for write, which prevents page faults by the parent process. This means if the anon_vma in question belongs to the parent process, no new pages will be added to it in this time. Likewise, if the anon_vma belonged to a grandparent process, any new pages instantiated in it will not be visible to the parent process, or to the newly created process. This means it is safe to skip the anon_vma. -- All rights reversed -- 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>