Hello, Daniel. On Wed, Oct 26, 2016 at 09:25:25PM +0200, Daniel Vetter wrote: > > > + * Note that callers must ensure that concurrent access to @ida is not possible. > > > + * When simplicity trumps concurrency needs look at ida_simple_get() instead. > > > > Maybe we can make it a bit less dramatic? > > What about? > > "Note that callers must ensure that concurrent access to @ida is not possible. > See ida_simple_get() for a varaint which takes care of locking. Yeah, that reads easier to me. > > Hmm... so, this isn't necessarily about speed. For example, id > > allocation might have to happen inside a spinlock which protects a > > larger scope. To guarantee GFP_KERNEL allocation behavior in such > > cases, the caller would have to call ida_pre_get() outside the said > > spinlock and then call ida_get_new_above() inside the lock. > > Hm, ida_simple_get does that for you already ... Here's an example. spin_lock(); do some stuff; something->id = ida_simple_get(some gfp flag); do some stuff; spin_unlock(); In this scenario, you can't use sleeping GFPs for ida_simple_get() because it does preloading inside it. What one has to do is... ida_pre_get(GFP_KERNEL); spin_lock(); do some stuff; something->id = ida_get_new_above(GFP_NOWAIT); do some stuff; spin_unlock(); So, I guess it can be sometimes about avoiding the extra locking overhead but it's more often about separating out allocation context into an earlier call. > > I think it'd be better to explain what the simple version does and > > expects and then say that unless there are specific requirements using > > the simple version is recommended. > > What about: > > "Compared to ida_get_new_above() this function does its own locking, and > should be used unless there are special requirements." Yeah, looks good to me. Thanks. -- tejun _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
