On 08/13, Rik van Riel wrote: > > On 08/13/2014 02:08 PM, Oleg Nesterov wrote: > > > > Well, I disagree. This is more complex, and this adds yet another lock > > which only protects the stats... > > The other lock is what can tell us that there is a writer active > NOW, which may be useful when it comes to guaranteeing forward > progress for readers when there are lots of threads exiting...
I don't really understand why seqcount_t is better in this sense, either way we need to to taking the lock if we want to guarantee a forward progress. read_seqbegin_or_lock() doesn't even work "automagically", and it can't be used in this case anyway. That said, it is not that I am really sure that seqcount_t in ->signal is actually worse, not to mention that this is subjective anyway. IOW, I am not going to really fight with your approach ;) > > Whatever we do, we should convert thread_group_cputime() to use > > for_each_thread() first(). > > What is the advantage of for_each_thread over while_each_thread, > besides getting rid of that t = tsk line? It is buggy and should die, see 0c740d0afc3bff0a097ad. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
