init, sched: Fix race between init and kthreadd
authorPeter Zijlstra <peterz@infradead.org>
Mon, 28 Jun 2010 14:51:01 +0000 (16:51 +0200)
committerIngo Molnar <mingo@elte.hu>
Mon, 28 Jun 2010 16:21:30 +0000 (18:21 +0200)
commitb433c3d4549ae74935b585115f076c6fb7bc48fe
treefa69951fe2dcdfed7482976d6d6fc0a0bd5d1d5d
parent0d98bb2656e9bd2dfda2d089db1fe1dbdab41504
init, sched: Fix race between init and kthreadd

Ilya reported that on a very slow machine he could reliably
reproduce a race between forking init and kthreadd. We first
fork init so that it  obtains pid-1, however since the scheduler
is already fully running at this point it can preempt and run
the init thread before we spawn and set kthreadd_task.

The init thread can then attempt spawning kthreads without
kthreadd being present which results in an OOPS.

Reported-by: Ilya Loginov <isloginov@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <1277736661.3561.110.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
init/main.c