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

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Message-ID: <20160426161621.34872b7f@gandalf.local.home>
Date:	Tue, 26 Apr 2016 16:16:21 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Tony Lindgren <tony@...mide.com>, linux-kernel@...r.kernel.org,
	mingo@...nel.org, Russell King <linux@....linux.org.uk>,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH arm 1/1] arm: Use _rcuidle tracepoint to allow use from
 idle

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

> On Tue, Apr 26, 2016 at 12:51:59PM -0700, Tony Lindgren wrote:
> > * Steven Rostedt <rostedt@...dmis.org> [160426 12:45]:  
> > > *Whack* *Whack* *Whack*!!!
> > > 
> > > Signed-off-by: Steven Rostedt <rostedt@...dmis.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@...ux.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@...dmis.org>

-- Steve