On Wed, 3 Apr 2013 16:50:55 +0200, Jan Kara <jack@xxxxxxx> wrote: > On Wed 03-04-13 18:21:46, Dmitry Monakhov wrote: > > inode store i_sync_tid and i_datasync_tid in order to optimize journal > > flushes and wait for commits only when necessary, but > > fields are declared as tid_t(not atomic_t as it done in ext3) so we > > have not synchronization between readers and writers, so gcc and cpu > > is allowed to perform prefetch, cache and other stuff. > > Looks like a bug, right? > Reads and writes to atomic_t aren't guaranteed to be any kind of a > barrier (if fact they are compiled as simple stores and loads on x86). Only > arithmetic operations on atomic types are special. So using tid_t is just > fine. Ok but what about prefetching? Compiler is allowed to prefetch on early stage ? should we use ACCESS_ONCE() or wmb() and rmb() here? > > Honza > -- > Jan Kara <jack@xxxxxxx> > SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
