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

Paul E. McKenney
2016-04-26T19:47:12Z

On Tue, Apr 26, 2016 at 12:39:50PM -0700, Tony Lindgren wrote:
> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> [160426 12:08]:
> > On Tue, Apr 26, 2016 at 11:29:39AM -0700, Tony Lindgren wrote:
> > > * Paul E. McKenney <paulmck@linux.vnet.ibm.com> [160426 10:53]:
> > > > Does the following patch help?
> > >
> > > It just changes the output.. See below.
> >
> > Ah -- you need both patches.
>
> Oops sorry, I though I had the first one already from next..
>
> > These are on -rcu at:
> >
> > 501889db6fee (arm: Use _rcuidle tracepoint to allow use from idle)
> > 99cd56ad86d2 (rm: Use more _rcuidle tracepoints to allow use from idle)
>
> With these omap4 is now OK. But omap3 produces yet another warning,
> See below :)

As Steven Rostedt said, whack-a-mole time...

The previous two patches are still needed.

Thanx, Paul

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

commit c7ab21af6d959e3541ea52427472fc5dece75023
Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Date: Tue Apr 26 12:43:57 2016 -0700

arm: Additional _rcuidle tracepoints to allow use from idle

This commit adds an _rcuidle suffix to a pair of trace events to
prevent the following splat:

> ===============================
> [ 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)

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 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);
}