On Mon, Aug 29, 2011 at 12:22:02AM -0700, Ying Han wrote: > fix hierarchy_walk() to hold a reference to first mem_cgroup > > The first mem_cgroup returned from hierarchy_walk() is used to > terminate a round-trip. However there is no reference hold on > that which the first could be removed during the walking. The > patch including the following change: > > 1. hold a reference on the first mem_cgroup during the walk. > 2. rename the variable "root" to "target", which we found using > "root" is confusing in this content with root_mem_cgroup. better > naming is welcomed. Thanks for the report. This was actually not the only case that could lead to overlong (not necessarily endless) looping. With several scanning threads, a single thread may not encounter its first cgroup again for a long time, as the other threads would visit it. I changed this to use scan generations. Restarting the scan from id 0 starts the next scan generation. The iteration function returns NULL if the generation changed since a loop was started. This way, iterators can reliably detect whether they should call it quits without any requirements for previously encountered memcgs. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>