On Mon, 5 Mar 2007 15:40:33 +0100 Andi Kleen <[EMAIL PROTECTED]> wrote:
> > It does seem risky. Perhaps it is a micro-optimisation which utilises > > knowledge that this thread_struct cannot be looked up via any path in this > > context. > > > > Or perhaps it is a bug. Andi, can you please comment? > > On flush_thread nobody else can mess with the thread, What about resched_task()? > so yes it's a micro > optimization. > > > > > > And about this specific flush_thread, I am puzzled about the t->flags ^= > > > (_TIF_ABI_PENDING | _TIF_IA32); line. The XOR will clearly flip the > > > _TIF_ABI_PENDING bit to 0, and very likely set _TIF_IA32 to the opposite > > > of its current value. Why does this change need to be written atomically > > > (can other threads play with these flags ?) ? > > > > > > > Don't know. > > iirc it came from DaveM originally. He just likes to write things in > comp^wclever ways :0) It's just a little shorter. > > > No, I don't immediately see anything in the flush_old_exec() code path > > which tells us that nobody else can look up this thread_info (or be holding > > a ref to it) in this context. > > Normally the process flags atomicity should only matter with signals; Thread flags. yes, most of them are synchronously set by their owner, but not all, I think. > i don't think you can send a signal to a process being in exec this way. > > -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
