On Wed, Feb 11, 2015 at 02:43:19PM -0500, Rik van Riel wrote: > If exception_enter happens when already in IN_KERNEL state, the > code still calls context_tracking_exit, which ends up in > rcu_eqs_exit_common, which explodes with a WARN_ON when it is > called in a situation where dynticks are not enabled. Fortunately context_tracking_exit() already has a current_state == IN_KERNEL check so this shouldn't be a problem. Meanwhile I'll still take the patch, it's better to handle that from the caller. Thanks. > > This can be avoided by having exception_enter only switch to > IN_KERNEL state if the current state is not already IN_KERNEL. > > Signed-off-by: Rik van Riel <riel@xxxxxxxxxx> > Reported-by: Luiz Capitulino <lcapitulino@xxxxxxxxxx> > --- > Frederic, you will want this "bonus" patch, too :) > > Thanks to Luiz for finding this one. Whatever I was running did not > trigger this issue... > > include/linux/context_tracking.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h > index b65fd1420e53..9da230406e8c 100644 > --- a/include/linux/context_tracking.h > +++ b/include/linux/context_tracking.h > @@ -37,7 +37,8 @@ static inline enum ctx_state exception_enter(void) > return 0; > > prev_ctx = this_cpu_read(context_tracking.state); > - context_tracking_exit(prev_ctx); > + if (prev_ctx != IN_KERNEL) > + context_tracking_exit(prev_ctx); > > return prev_ctx; > } > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
