Ingo Molnar <mingo@xxxxxxxxxx> wrote: > I think this is too complex. > > How about something simple like the patch below (on top of the third patch)? > It makes the vmalloc info transactional - /proc/meminfo will always print a > consistent set of numbers. (Not that we really care about races there, but it > looks really simple to solve so why not.) Looks like a huge simplification! It needs a comment about the approximate nature of the locking and the obvious race conditions: 1) The first caller to get_vmalloc_info() clears vmap_info_changed before updating vmap_info_cache, so a second caller is likely to get stale data for the duration of a calc_vmalloc_info call. 2) Although unlikely, it's possible for two threads to race calling calc_vmalloc_info, and the one that computes fresher data updates the cache first, so the later write leaves stale data. Other issues: 3) Me, I'd make vmap_info_changed a bool, for documentation more than any space saving. 4) I wish there were a trylock version of write_seqlock, so we could avoid blocking entirely. (You *could* hand-roll it, but that eats into the simplicity.) -- 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>