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...@intel.com> 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?
I've queued test jobs for this patch, will let you know once I get the
result.
Thanks,
Xiaolong
>
> Thanx, Paul
>
>------------------------------------------------------------------------
>
>commit ccc0666e2049e5818c236e647cf20c552a7b053b
>Author: Paul E. McKenney <paul...@linux.vnet.ibm.com>
>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 <paul...@linux.vnet.ibm.com>
>
>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)
>
>
