Re: [PATCH arm 1/1] arm: Use _rcuidle tracepoint to allow use from idle

Paul E. McKenney
2016-04-26T20:41:17Z

On Tue, Apr 26, 2016 at 01:25:39PM -0700, Tony Lindgren wrote:
> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> [160426 13:12]:
> > On Tue, Apr 26, 2016 at 01:06:13PM -0700, Paul E. McKenney wrote:
> > > On Tue, Apr 26, 2016 at 12:51:59PM -0700, Tony Lindgren wrote:
> > > > * Steven Rostedt <rostedt@goodmis.org> [160426 12:45]:
> > > > > *Whack* *Whack* *Whack*!!!
> > > > >
> > > > > Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> > > > > ---
> > > > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> > > > > index fb74dc1f7520..4fa43c02d682 100644
> > > > > --- a/drivers/clk/clk.c
> > > > > +++ b/drivers/clk/clk.c
> > > > > @@ -682,12 +682,12 @@ static void clk_core_disable(struct clk_core *core)
> > > > > if (--core->enable_count > 0)
> > > > > return;
> > > > >
> > > > > - trace_clk_disable(core);
> > > > > + trace_clk_disable_rcuidle(core);
> > > > >
> > > > > if (core->ops->disable)
> > > > > core->ops->disable(core->hw);
> > > > >
> > > > > - trace_clk_disable_complete(core);
> > > > > + trace_clk_disable_complete_rcuidle(core);
> > > > >
> > > > > clk_core_disable(core->parent);
> > > > > }
> > > >
> > > > Now the mole shows up here!
> > >
> > > And the patch shows up here!
> >
> > And I bet you will need this one as well...
>
> OK and now the mode is coming back after a short nap during idle:

Seems a bit unfair to whack it just after a short nap, but here goes!

Thanx, Paul

------------------------------------------------------------------------

commit 5c8e9cffebfc02acfbcfd18b46a6b1dbce96cbe3
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Tue Apr 26 13:38:55 2016 -0700

arm: Whack yet another event-trace-from-idle mole

This commit applies another _rcuidle suffix to fix an RCU use from
idle.

> ===============================
> [ INFO: suspicious RCU usage. ]
> 4.6.0-rc5-next-20160426+ #1122 Not tainted
> -------------------------------
> include/trace/events/rpm.h:69 suspicious rcu_dereference_check() usage!
>
> other info that might help us debug this:
>
>
> RCU used illegally from idle CPU!
> rcu_scheduler_active = 1, debug_locks = 0
> RCU used illegally from extended quiescent state!
> 1 lock held by swapper/0/0:
> #0: (&(&dev->power.lock)->rlock){-.-...}, at: [<c052e3dc>] __pm_runtime_resume+0x3c/0x64
>
> stack backtrace:
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.6.0-rc5-next-20160426+ #1122
> Hardware name: Generic OMAP36xx (Flattened Device Tree)
> [<c0110290>] (unwind_backtrace) from [<c010c3a8>] (show_stack+0x10/0x14)
> [<c010c3a8>] (show_stack) from [<c047fd68>] (dump_stack+0xb0/0xe4)
> [<c047fd68>] (dump_stack) from [<c052e178>] (rpm_resume+0x5cc/0x7f4)
> [<c052e178>] (rpm_resume) from [<c052e3ec>] (__pm_runtime_resume+0x4c/0x64)
> [<c052e3ec>] (__pm_runtime_resume) from [<c04bf2c4>] (omap2_gpio_resume_after_idle+0x54/0x68)
> [<c04bf2c4>] (omap2_gpio_resume_after_idle) from [<c01269dc>] (omap3_enter_idle_bm+0xfc/0x1ec)
> [<c01269dc>] (omap3_enter_idle_bm) from [<c060198c>] (cpuidle_enter_state+0x80/0x3d4)
> [<c060198c>] (cpuidle_enter_state) from [<c0183b08>] (cpu_startup_entry+0x198/0x3a0)
> [<c0183b08>] (cpu_startup_entry) from [<c0b00c0c>] (start_kernel+0x354/0x3c8)
> [<c0b00c0c>] (start_kernel) from [<8000807c>] (0x8000807c)

Reported-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: <linux-omap@vger.kernel.org>
Cc: <linux-arm-kernel@lists.infradead.org>

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index e4c2b8fdeff3..15b6d5b199d4 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -601,7 +601,7 @@ static int rpm_resume(struct device *dev, int rpmflags)
struct device *parent = NULL;
int retval = 0;

- trace_rpm_resume(dev, rpmflags);
+ trace_rpm_resume_rcuidle(dev, rpmflags);

repeat:
if (dev->power.runtime_error)
@@ -764,7 +764,7 @@ static int rpm_resume(struct device *dev, int rpmflags)
spin_lock_irq(&dev->power.lock);
}

- trace_rpm_return_int(dev, _THIS_IP_, retval);
+ trace_rpm_return_int_rcuidle(dev, _THIS_IP_, retval);

return retval;
}