Re: [lkp] [mm] e7c1db75fe: BUG:sleeping_function_called_from_invalid_context_at_mm/page_alloc.c

[Paul E. McKenney]

On Tue, Nov 29, 2016 at 05:21:19PM +0000, Sudeep Holla wrote:
> On Sun, Nov 27, 2016 at 6:16 PM, kernel test robot
> <xiaolong.ye@xxxxxxxxx> wrote:
> >
> > FYI, we noticed the following commit:
> >
> > commit e7c1db75fed821a961ce1ca2b602b08e75de0cd8 ("mm: Prevent __alloc_pages_nodemask() RCU CPU stall warnings")
> > https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/next
> >
> > in testcase: boot
> >
> > on test machine: qemu-system-x86_64 -enable-kvm -cpu Nehalem -smp 2 -m 1G
> >
> > caused below changes:
> >
> [...]
> 
> > [    8.953192] BUG: sleeping function called from invalid context at mm/page_alloc.c:3746
> > [    8.956353] in_atomic(): 1, irqs_disabled(): 1, pid: 0, name: swapper/0
> 
> I am observing similar BUG/backtrace even on ARM64 platform.

Does the (untested) patch below help?

							Thanx, Paul

------------------------------------------------------------------------

commit ccc0666e2049e5818c236e647cf20c552a7b053b
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Date:   Tue Nov 29 11:06:05 2016 -0800

    rcu: Allow boot-time use of cond_resched_rcu_qs()
    
    The cond_resched_rcu_qs() macro is used to force RCU quiescent states into
    long-running in-kernel loops.  However, some of these loops can execute
    during early boot when interrupts are disabled, and during which time
    it is therefore illegal to enter the scheduler.  This commit therefore
    makes cond_resched_rcu_qs() be a no-op during early boot.
    
    Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 525ca34603b7..8b4b1be8095b 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -423,7 +423,7 @@ extern struct srcu_struct tasks_rcu_exit_srcu;
  */
 #define cond_resched_rcu_qs() \
 do { \
-	if (!cond_resched()) \
+	if (rcu_scheduler_active && !cond_resched()) \
 		rcu_note_voluntary_context_switch(current); \
 } while (0)