On Mon, Sep 28, 2020 at 10:33:13AM -0700, Paul E. McKenney wrote:
> On Mon, Sep 28, 2020 at 09:57:29AM +0200, Peter Zijlstra wrote:
> > On Thu, Sep 17, 2020 at 11:00:05AM -0700, Paul E. McKenney wrote:
> > > On Thu, Sep 17, 2020 at 01:26:52PM +1000, Stephen Rothwell wrote:
> > > > Hi all,
> > > >
> > > > Commit
> > > >
> > > > 903c5302fa2d ("sched/core: Allow try_invoke_on_locked_down_task() with irqs disabled")
> > > >
> > > > is missing a Signed-off-by from its author and committer.
> > > >
> > > > I didn't complain about this when it was first present because I figured
> > > > it was just a debugging commit that would be removed quickly. However,
> > > > there are now quite a few follow up commits ...
> > >
> > > Without Peter's Signed-off-by, I clearly won't be submitting it to the
> > > upcoming merge window.
> > >
> > > Peter, this is now quite close to your original patch. May I please
> > > add your Signed-off-by?
> >
> > Sure!
>
> Much appreciated!!!
>
> But I already replaced that commit with one that moves the call to
> try_invoke_on_locked_down_task() an interrupts-enabled region of code.
> Which is probably what I should have done to start with... :-/
Except that Marco Elver is making that fail, so I am resuscitating your
patch with your Signed-off-by, as shown below.
So once again, much appreciated!!!
Thanx, Paul
------------------------------------------------------------------------
commit 444ef3bbd0f243b912fdfd51f326704f8ee872bf
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Sat Aug 29 10:22:24 2020 -0700
sched/core: Allow try_invoke_on_locked_down_task() with irqs disabled
The try_invoke_on_locked_down_task() function currently requires
that interrupts be enabled, but it is called with interrupts
disabled from rcu_print_task_stall(), resulting in an "IRQs not
enabled as expected" diagnostic. This commit therefore updates
try_invoke_on_locked_down_task() to use raw_spin_lock_irqsave() instead
of raw_spin_lock_irq(), thus allowing use from either context.
Link: https://lore.kernel.org/lkml/000000000000903d5805ab908fc4@xxxxxxxxxx/
Link: https://lore.kernel.org/lkml/20200928075729.GC2611@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
Reported-by: syzbot+cb3b69ae80afd6535b0e@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e172f2d..09ef5cf 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2984,7 +2984,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
/**
* try_invoke_on_locked_down_task - Invoke a function on task in fixed state
- * @p: Process for which the function is to be invoked.
+ * @p: Process for which the function is to be invoked, can be @current.
* @func: Function to invoke.
* @arg: Argument to function.
*
@@ -3002,12 +3002,11 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
*/
bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct task_struct *t, void *arg), void *arg)
{
- bool ret = false;
struct rq_flags rf;
+ bool ret = false;
struct rq *rq;
- lockdep_assert_irqs_enabled();
- raw_spin_lock_irq(&p->pi_lock);
+ raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
if (p->on_rq) {
rq = __task_rq_lock(p, &rf);
if (task_rq(p) == rq)
@@ -3024,7 +3023,7 @@ bool try_invoke_on_locked_down_task(struct task_struct *p, bool (*func)(struct t
ret = func(p, arg);
}
}
- raw_spin_unlock_irq(&p->pi_lock);
+ raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags);
return ret;
}
