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

Paul E. McKenney
2016-04-26T20:05:44Z

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!

Thanx, Paul

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

commit d824fb6beb6e23ade51806e11a882528dc15ae98
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Tue Apr 26 13:03:51 2016 -0700

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

This commit appends a few _rcuidle suffixes to fix the following
RCU-used-from-idle bug:

> ===============================
> [ INFO: suspicious RCU usage. ]
> 4.6.0-rc5-next-20160426+ #1116 Not tainted
> -------------------------------
> include/trace/events/rpm.h:95 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: [<c052cc2c>] __rpm_callback+0x58/0x60
>
> stack backtrace:
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.6.0-rc5-next-20160426+ #1116
> 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 [<c052d5d0>] (rpm_suspend+0x580/0x768)
> [<c052d5d0>] (rpm_suspend) from [<c052ec58>] (__pm_runtime_suspend+0x64/0x84)
> [<c052ec58>] (__pm_runtime_suspend) from [<c04bf25c>] (omap2_gpio_prepare_for_idle+0x5c/0x70)
> [<c04bf25c>] (omap2_gpio_prepare_for_idle) from [<c0125568>] (omap_sram_idle+0x140/0x244)
> [<c0125568>] (omap_sram_idle) from [<c01269dc>] (omap3_enter_idle_bm+0xfc/0x1ec)
> [<c01269dc>] (omap3_enter_idle_bm) from [<c0601bdc>] (cpuidle_enter_state+0x80/0x3d4)
> [<c0601bdc>] (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)

In the immortal words of Steven Rostedt, "*Whack* *Whack* *Whack*!!!"

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 d9358c202763..af4c38d41aff 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -301,7 +301,7 @@ static int rpm_idle(struct device *dev, int rpmflags)
int (*callback)(struct device *);
int retval;

- trace_rpm_idle(dev, rpmflags);
+ trace_rpm_idle_rcuidle(dev, rpmflags);
retval = rpm_check_suspend_allowed(dev);
if (retval < 0)
; /* Conditions are wrong. */
@@ -337,7 +337,7 @@ static int rpm_idle(struct device *dev, int rpmflags)
dev->power.request_pending = true;
queue_work(pm_wq, &dev->power.work);
}
- trace_rpm_return_int(dev, _THIS_IP_, 0);
+ trace_rpm_return_int_rcuidle(dev, _THIS_IP_, 0);
return 0;
}

@@ -352,7 +352,7 @@ static int rpm_idle(struct device *dev, int rpmflags)
wake_up_all(&dev->power.wait_queue);

out:
- trace_rpm_return_int(dev, _THIS_IP_, retval);
+ trace_rpm_return_int_rcuidle(dev, _THIS_IP_, retval);
return retval ? retval : rpm_suspend(dev, rpmflags | RPM_AUTO);
}