From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nigel Cunningham Subject: Re: [linux-pm] [PATCH] Threads shouldn't inherit PF_NOFREEZE Date: Thu, 20 Oct 2005 07:01:17 +1000 Message-ID: <1129755676.4577.51.camel@localhost> References: Reply-To: ncunningham@cyclades.com Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Alan Stern Cc: Andrew Morton , Rusty Russell , Linus Torvalds , Pavel Machek , Linux-pm mailing list , Kernel development list List-Id: linux-pm@vger.kernel.org Hi Alan. On Wed, 2005-10-19 at 05:29, Alan Stern wrote: > The PF_NOFREEZE process flag should not be inherited when a thread is > forked. This patch (as585) removes the flag from the child. > > This problem is starting to show up more and more as drivers turn to the > kthread API instead of using kernel_thread(). As a result, their kernel > threads are now children of the kthread worker instead of modprobe, and > they inherit the PF_NOFREEZE flag. This can cause problems during system > suspend; the kernel threads are not getting frozen as they ought to be. > > Alan Stern I have this in kthread instead, so that multithreaded userspace processes only need to have NOFREEZE set once (before forking). Yes, I have one that fits this scenario - I'm working on a userspace storage maanger, which will setup and tear down a network connection at appropriate times during a suspend-to-disk cycle. The initial version is based on nbd and uses two threads because the one that sets up storage blocks in a syscall as Pavel & others have written it. Anyway, I agree that the general need you're trying to address is real. Regards, Nigel > > > Signed-off-by: Alan Stern > > --- > > What I said above may not be quite true. For all I know, there may be > threads which rely on inheriting PF_NOFREEZE from their parent. But it > should not be inherited by default. > > Index: usb-2.6/kernel/fork.c > =================================================================== > --- usb-2.6.orig/kernel/fork.c > +++ usb-2.6/kernel/fork.c > @@ -848,7 +848,7 @@ static inline void copy_flags(unsigned l > { > unsigned long new_flags = p->flags; > > - new_flags &= ~PF_SUPERPRIV; > + new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE); > new_flags |= PF_FORKNOEXEC; > if (!(clone_flags & CLONE_PTRACE)) > p->ptrace = 0; > > > ______________________________________________________________________ > _______________________________________________ > linux-pm mailing list > linux-pm@lists.osdl.org > https://lists.osdl.org/mailman/listinfo/linux-pm --