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

[Ye Xiaolong]

On 11/29, Paul E. McKenney wrote:
>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

Hi, Paul

I applied your patch on top of 2d66ccc "mm:
Prevent__alloc_pages_nodemask() RCU CPU stall warnings"(e7c1db7 turns to
2d66ccc in rcu/next branch now), here is the comparison of 6 times
testing, seems the BUG persists.

b70fa84d2eeef5f6be25633a2b is the commit id of commit "rcu: Allow
boot-time useof cond_resched_rcu_qs()" 

testcase/path_params/tbox_group/run: boot/1/vm-vp-1G

2d66cccd73436ac9  b70fa84d2eeef5f6be25633a2b  
----------------  --------------------------  
          6:6            0%           6:6     dmesg.BUG:sleeping_function_called_from_invalid_context_at_mm/page_alloc.c

Thanks,
Xiaolong
>
>------------------------------------------------------------------------
>
>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)
> 
>