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

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Message-ID: <20160426200613.GO3715@linux.vnet.ibm.com>
Date:	Tue, 26 Apr 2016 13:06:13 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>, 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 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*!!!"
    
    Reported-by: Tony Lindgren <tony@...mide.com>
    Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
    Cc: Tony Lindgren <tony@...mide.com>
    Cc: Russell King <linux@....linux.org.uk>
    Cc: Steven Rostedt <rostedt@...dmis.org>
    Cc: <linux-omap@...r.kernel.org>
    Cc: <linux-arm-kernel@...ts.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);
 }