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

Paul E. McKenney
2016-04-26T21:10:04Z

On Tue, Apr 26, 2016 at 01:46:15PM -0700, Tony Lindgren wrote:
> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> [160426 13:42]:
> > 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!
>
> This mode seems pretty hard headed :) Now clk_core_enable:

Nah, just a lot of heads...

Thanx, Paul

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

commit 21c3fc2373886a9fa014f0f69a72186377758f4b
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Tue Apr 26 14:02:23 2016 -0700

arm: Whack an expected event-trace-from-idle mole

This commit fixes the RCU use-from-idle bug corresponding the following
splat:

> [ INFO: suspicious RCU usage. ]
> 4.6.0-rc5-next-20160426+ #1127 Not tainted
> -------------------------------
> include/trace/events/clk.h:45 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!
> 2 locks held by swapper/0/0:
> #0: (&oh->hwmod_key#30){......}, at: [<c0121afc>] omap_hwmod_enable+0x18/0x44
> #1: (enable_lock){......}, at: [<c0630684>] clk_enable_lock+0x18/0x124
>
> stack backtrace:
> CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.6.0-rc5-next-20160426+ #1127
> 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 [<c06315c0>] (clk_core_enable+0x1e0/0x36c)
> [<c06315c0>] (clk_core_enable) from [<c0632298>] (clk_enable+0x1c/0x38)
> [<c0632298>] (clk_enable) from [<c01204e0>] (_enable_clocks+0x18/0x7c)
> [<c01204e0>] (_enable_clocks) from [<c012137c>] (_enable+0x114/0x2ec)
> [<c012137c>] (_enable) from [<c0121b08>] (omap_hwmod_enable+0x24/0x44)
> [<c0121b08>] (omap_hwmod_enable) from [<c0122ad0>] (omap_device_enable+0x3c/0x90)
> [<c0122ad0>] (omap_device_enable) from [<c0122b34>] (_od_runtime_resume+0x10/0x38)
> [<c0122b34>] (_od_runtime_resume) from [<c052cc00>] (__rpm_callback+0x2c/0x60)
> [<c052cc00>] (__rpm_callback) from [<c052cc54>] (rpm_callback+0x20/0x80)
> [<c052cc54>] (rpm_callback) from [<c052df7c>] (rpm_resume+0x3d0/0x6f0)
> [<c052df7c>] (rpm_resume) from [<c052e2e8>] (__pm_runtime_resume+0x4c/0x64)
> [<c052e2e8>] (__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 [<c0601888>] (cpuidle_enter_state+0x80/0x3d4)
> [<c0601888>] (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/clk/clk.c b/drivers/clk/clk.c
index 4fa43c02d682..ec83f404c1d2 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -735,12 +735,12 @@ static int clk_core_enable(struct clk_core *core)
if (ret)
return ret;

- trace_clk_enable(core);
+ trace_clk_enable_rcuidle(core);

if (core->ops->enable)
ret = core->ops->enable(core->hw);

- trace_clk_enable_complete(core);
+ trace_clk_enable_complete_rcuidle(core);

if (ret) {
clk_core_disable(core->parent);