Messages in this thread | | | Subject | Re: next: Commit 'mm: Prevent __alloc_pages_nodemask() RCU CPU stall ...' causing hang on sparc32 qemu | From | Guenter Roeck <> | Date | Tue, 29 Nov 2016 20:32:51 -0800 |
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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 <paulmck@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 <paulmck@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) > { > } > >
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