Messages in this thread | | | Date | Wed, 21 Mar 2007 14:50:27 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] reject taskset for kernel threads |
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On Wed, 21 Mar 2007 21:53:53 +0100 Olaf Hering <olaf@aepfle.de> wrote:
> > Do not allow taskset for kernel threads. > These commands will cause oopses due to stack corruption: > > ls /proc/*/task | grep -v ^/ | xargs echo | xargs -n1 taskset -pc 2-9 > taskset -pc 1 $$ > taskset -pc 0 $((pidof john))
Why does the kernel oops?
> Possible fix in userland: > > for i in ` ls /proc/*/task | grep -v ^/ ` > do > e=/proc/*/task/$i/exe > if test -e $e > then > taskset -pc 2-9 $i > fi > done > > > Signed-off-by: Olaf Hering <olaf@aepfle.de> > > --- > kernel/sched.c | 2 ++ > 1 file changed, 2 insertions(+) > > Index: linux-2.6.20/kernel/sched.c > =================================================================== > --- linux-2.6.20.orig/kernel/sched.c > +++ linux-2.6.20/kernel/sched.c > @@ -4310,6 +4310,8 @@ long sched_setaffinity(pid_t pid, cpumas > read_unlock(&tasklist_lock); > > retval = -EPERM; > + if (!p->mm) > + goto out_unlock; > if ((current->euid != p->euid) && (current->euid != p->uid) && > !capable(CAP_SYS_NICE)) > goto out_unlock;
Maybe. There are some kernel threads for which we definitely don't want the affinity altered (ksoftirqd, probably keventd..). But otoh there might be legitimate reasons to alter, say, pdflush's or kjournald's affinity, and that should be a safe thing to do.
Perhaps a suitable compromise would be to disallow affinity-setting on non-singlethreaded kernel threads. But of course, we don't want that to oops.
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