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

Steven Rostedt
2016-04-26T20:16:27Z

On Tue, 26 Apr 2016 13:06:13 -0700
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> 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!
>
> 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*!!!"

WhACKED-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve