On 11/29/2016 05:28 PM, Paul E. McKenney wrote:
On Tue, Nov 29, 2016 at 01:23:08PM -0800, Guenter Roeck wrote:
Hi Paul,
most of my qemu tests for sparc32 targets started to fail in next-20161129.
The problem is only seen in SMP builds; non-SMP builds are fine.
Bisect points to commit 2d66cccd73436 ("mm: Prevent __alloc_pages_nodemask()
RCU CPU stall warnings"); reverting that commit fixes the problem.
Test scripts are available at:
https://github.com/groeck/linux-build-test/tree/master/rootfs/sparc
Test results are at:
https://github.com/groeck/linux-build-test/tree/master/rootfs/sparc
Bisect log is attached.
Please let me know if there is anything I can do to help tracking down the
problem.
Apologies!!! Does the patch below help?
No, sorry, it doesn't make a difference.
Guenter
Thanx, Paul
------------------------------------------------------------------------
commit 97708e737e2a55fed4bdbc005bf05ea909df6b73
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..b6944cc19a07 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 (!is_idle_task(current) && !cond_resched()) \
rcu_note_voluntary_context_switch(current); \
} while (0)
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 7232d199a81c..20f5990deeee 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -228,6 +228,7 @@ static inline void exit_rcu(void)
extern int rcu_scheduler_active __read_mostly;
void rcu_scheduler_starting(void);
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+#define rcu_scheduler_active false
static inline void rcu_scheduler_starting(void)
{
}
