On Sat, 2011-05-14 at 20:12 +0900, KOSAKI Motohiro wrote: > >> Can you please explain why we should use seqlock? That said, > >> we didn't use seqlock for /proc items. because, plenty seqlock > >> write may makes readers busy wait. Then, if we don't have another > >> protection, we give the local DoS attack way to attackers. > > > > So you're saying that heavy write contention can cause reader > > starvation? > > Yes. > > >> task->comm is used for very fundamentally. then, I doubt we can > >> assume write is enough rare. Why can't we use normal spinlock? > > > > I think writes are likely to be fairly rare. Tasks can only name > > themselves or sibling threads, so I'm not sure I see the risk here. > > reader starvation may cause another task's starvation if reader have > an another lock. So the risk is a thread rewriting its own comm over and over could starve some other critical task trying to read the comm. Ok. It makes it a little more costly, but fair enough. thanks -john -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>