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

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Message-ID: <20160426190755.GK3715@linux.vnet.ibm.com>
Date:	Tue, 26 Apr 2016 12:07:55 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org,
	Russell King <linux@....linux.org.uk>,
	Steven Rostedt <rostedt@...dmis.org>,
	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 11:29:39AM -0700, Tony Lindgren wrote:
> * Paul E. McKenney <paulmck@...ux.vnet.ibm.com> [160426 10:53]:
> > Does the following patch help?
> 
> It just changes the output.. See below.

Ah -- you need both patches.

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)

And -rcu may be found at:

	git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git

							Thanx, Paul

> > It is quite possible that there are quite a few more of these.  If this
> > is the case, then one way to make the kernel list more of them on a
> > given boot is to build with CONFIG_PROVE_RCU_REPEATEDLY=y.
> 
> OK
> 
> Regards,
> 
> Tony
> 
> 8< ------------------
> CPU: Testing write buffer coherency: ok
> CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
> 
> 
> RCU used illegally from idle CPU!
> rcu_scheduler_active = 1, debug_locks = 0
> RCU used illegally from extended quiescent state!
> no locks held by swapper/1/0.
> 
> stack backtrace:
> CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.6.0-rc5-next-20160426+ #1113
> Hardware name: Generic OMAP4 (Flattened Device Tree)
> [<c0110290>] (unwind_backtrace) from [<c010c3a8>] (show_stack+0x10/0x14)
> [<c010c3a8>] (show_stack) from [<c047ff88>] (dump_stack+0xb0/0xe4)
> [<c047ff88>] (dump_stack) from [<c012c014>] (pwrdm_set_next_pwrst+0x100/0x1d4)
> [<c012c014>] (pwrdm_set_next_pwrst) from [<c0126120>] (omap4_enter_lowpower+0xc8/0x230)
> [<c0126120>] (omap4_enter_lowpower) from [<c0126c24>] (omap_enter_idle_coupled+0x6c/0x254)
> [<c0126c24>] (omap_enter_idle_coupled) from [<c0601dfc>] (cpuidle_enter_state+0x80/0x3d4)
> [<c0601dfc>] (cpuidle_enter_state) from [<c0603d30>] (cpuidle_enter_state_coupled+0x348/0x390)
> [<c0603d30>] (cpuidle_enter_state_coupled) from [<c0183d34>] (cpu_startup_entry+0x198/0x3a0)
> [<c0183d34>] (cpu_startup_entry) from [<8010162c>] (0x8010162c)
> hw-breakpoint: Failed to enable monitor mode on CPU 0.
>