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

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Message-ID: <20160426195121.GN3715@linux.vnet.ibm.com>
Date:	Tue, 26 Apr 2016 12:51:21 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Steven Rostedt <rostedt@...dmis.org>
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, Apr 26, 2016 at 03:44:14PM -0400, Steven Rostedt wrote:
> On Tue, 26 Apr 2016 12:39:50 -0700
> Tony Lindgren <tony@...mide.com> wrote:
> 
> 
> > With these omap4 is now OK. But omap3 produces yet another warning,
> > See below :)
> > 
> > Regards,
> > 
> > Tony
> > 
> > 8< ------------------
> > ===============================
> > [ INFO: suspicious RCU usage. ]
> > 4.6.0-rc5-next-20160426+ #1114 Not tainted
> > -------------------------------
> > include/trace/events/clk.h:59 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: [<c0121b40>] omap_hwmod_idle+0x18/0x44
> >  #1:  (enable_lock){......}, at: [<c0630998>] clk_enable_lock+0x18/0x124
> > 
> > stack backtrace:
> > CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.6.0-rc5-next-20160426+ #1114
> > 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 [<c0631618>] (clk_core_disable+0x17c/0x348)
> > [<c0631618>] (clk_core_disable) from [<c0632774>] (clk_disable+0x24/0x30)
> > [<c0632774>] (clk_disable) from [<c0120590>] (_disable_clocks+0x18/0x7c)
> > [<c0120590>] (_disable_clocks) from [<c0121680>] (_idle+0x12c/0x230)
> > [<c0121680>] (_idle) from [<c0121b4c>] (omap_hwmod_idle+0x24/0x44)
> > [<c0121b4c>] (omap_hwmod_idle) from [<c0122c24>] (omap_device_idle+0x3c/0x90)
> > [<c0122c24>] (omap_device_idle) from [<c052cc00>] (__rpm_callback+0x2c/0x60)
> > [<c052cc00>] (__rpm_callback) from [<c052cc54>] (rpm_callback+0x20/0x80)
> > [<c052cc54>] (rpm_callback) from [<c052d150>] (rpm_suspend+0x100/0x768)
> > [<c052d150>] (rpm_suspend) from [<c052ec58>] (__pm_runtime_suspend+0x64/0x84)
> > [<c052ec58>] (__pm_runtime_suspend) from [<c04bf25c>] (omap2_gpio_prepare_for_idle+0x5
> > c/0x70)
> > [<c04bf25c>] (omap2_gpio_prepare_for_idle) from [<c0125568>] (omap_sram_idle+0x140/0x2
> > 44)
> > [<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)
> 
> *Whack* *Whack* *Whack*!!!
> 
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>

Or use Steven's identical patch, your choice.  ;-)

							Thanx, Paul

> ---
> 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);
>  }
>