On Thu, Aug 30, 2012 at 02:05:27PM -0700, Paul E. McKenney wrote: > From: Frederic Weisbecker <[email protected]> > > When an exception or an irq exits, and we are going to resume into > interrupted kernel code, the low level architecture code calls > preempt_schedule_irq() if there is a need to reschedule. > > If the interrupt/exception occured between a call to rcu_user_enter() > (from syscall exit, exception exit, do_notify_resume exit, ...) and > a real resume to userspace (iret,...), preempt_schedule_irq() can be > called whereas RCU thinks we are in userspace. But preempt_schedule_irq() > is going to run kernel code and may be some RCU read side critical > section. We must exit the userspace extended quiescent state before > we call it. > > To solve this, just call rcu_user_exit() in the beginning of > preempt_schedule_irq(). > > Signed-off-by: Frederic Weisbecker <[email protected]> > Cc: Alessio Igor Bogani <[email protected]> > Cc: Andrew Morton <[email protected]> > Cc: Avi Kivity <[email protected]> > Cc: Chris Metcalf <[email protected]> > Cc: Christoph Lameter <[email protected]> > Cc: Geoff Levand <[email protected]> > Cc: Gilad Ben Yossef <[email protected]> > Cc: Hakan Akkan <[email protected]> > Cc: H. Peter Anvin <[email protected]> > Cc: Ingo Molnar <[email protected]> > Cc: Josh Triplett <[email protected]> > Cc: Kevin Hilman <[email protected]> > Cc: Max Krasnyansky <[email protected]> > Cc: Peter Zijlstra <[email protected]> > Cc: Stephen Hemminger <[email protected]> > Cc: Steven Rostedt <[email protected]> > Cc: Sven-Thorsten Dietrich <[email protected]> > Cc: Thomas Gleixner <[email protected]> > Signed-off-by: Paul E. McKenney <[email protected]>
Reviewed-by: Josh Triplett <[email protected]> > kernel/sched/core.c | 1 + > 1 files changed, 1 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 07c6d9a..0bd599b 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3564,6 +3564,7 @@ asmlinkage void __sched preempt_schedule_irq(void) > /* Catch callers which need to be fixed */ > BUG_ON(ti->preempt_count || !irqs_disabled()); > > + rcu_user_exit(); > do { > add_preempt_count(PREEMPT_ACTIVE); > local_irq_enable(); > -- > 1.7.8 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
