Hi! > > If frozen is atomic_t, do we need memory barrier? > > I think so. For example on x86-64 atomic_read() is just a read.
I'm not sure, but for x86-64 barriers are nops, anyway, IIRC. > > > @@ -128,6 +135,21 @@ static unsigned int try_to_freeze_tasks( > > > } while_each_thread(g, p); > > > read_unlock(&tasklist_lock); > > > yield(); /* Yield is okay here */ > > > + if (!todo) { > > > + /* Make sure that none of the stopped processes has > > > + * received the continuation signal after we checked > > > + * last time. > > > + */ > > > > I do not like the counting idea; it should be simpler to just check if > > all the processes are still stopped. > > I thought about that but didn't invent anything reasonable enough. > > > But I'm not sure if this is enough. What if signal is being delivered > > on another CPU while freezing, still being delivered while this second > > check runs, and then SIGCONT is delivered? > > Hm, is this possible in practice? I mean, if todo is 0 and nr_stopped doesn't > change, then there are no processes that can send the SIGCONT (unless someone > creates a kernel thread with PF_NOFREEZE that will do just that). No, SIGCONT was sent before freezing even started, and for some reason takes long time on other CPU. [Of course it is going to be quite hard to hit that race _in practice_ and mdelay(1000) before check would solve it for practical purposes...?] > Anyway, for now I've no idea how to fix this properly. Will think about it > tomorrow. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Suspend-devel mailing list Suspend-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/suspend-devel