On 05/16, Sasha Levin wrote: > > On 04/13/2014 03:56 PM, Oleg Nesterov wrote: > > 1. Remove CLONE_KERNEL, it has no users and it is dangerous. > > > > The (old) comment says "List of flags we want to share for kernel > > threads" but this is not true, we do not want to share ->sighand by > > default. This flag can only be used if the caller is sure that both > > parent/child will never play with signals (say, allow_signal/etc). > > > > 2. Change rest_init() to clone kernel_init() without CLONE_SIGHAND. > > > > In this case CLONE_SIGHAND does not really hurt, and it looks like > > optimization because copy_sighand() can avoid kmem_cache_alloc(). > > > > But in fact this only adds the minor pessimization. kernel_init() > > is going to exec the init process, and de_thread() will need to > > unshare ->sighand and do kmem_cache_alloc(sighand_cachep) anyway, > > but it needs to do more work and take tasklist_lock and siglock. > > > > Signed-off-by: Oleg Nesterov <[email protected]> > > Hi Oleg, > > This patch triggers a hang during boot in my KVM guest.
Hmm... How??? ;) > There are no > messages or anything, it just hangs right before init is supposed to > start up. Do you mean kernel_init() hangs somewhere in run_init_process() paths? > I've narrowed it down a bit, and it's the removal of CLONE_SIGHAND > that's bothering it. This must not be possible, I bet there is something else which should be fixed. > Removing CLONE_FS and CLONE_FILES doesn't > cause the hang on boot. kernel_thread(kernel_init) doesn't use CLONE_FILES ? Oleg. -- 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/
