On Mon, Jan 14, 2008 at 02:21:45PM +1100, Neil Brown wrote: > Maybe it isn't there any more.... > > Once upon a time, when I > echo remove > /sys/block/mdX/md/dev-YYY/state Egads. And just what will protect you from parallel callers of state_store()? buffer->mutex does *not* do that - it only gives you exclusion on given struct file. Run the command above from several shells and you've got independent open from each redirect => different struct file *and* different buffer for each => no exclusion whatsoever. And _that_ is present right in the mainline tree - it's unrelated to -mm kobject changes. BTW, yes, you do have a deadlock there - kobject_del() will try to evict children, which will include waiting for currently running ->store() to finish, which will include the caller since .../state *is* a child of that sucker. The real problem is the lack of any kind of exclusion considerations in md.c itself, AFAICS. Fun with ordering is secondary (BTW, yes, it is a problem - will sysfs ->store() to attribute between export_rdev() and kobject_del() work correctly?) - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
