linux-kernel - Re: [PATCH] powerpc: tracing: don't trace hcalls on offline CPUs

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Date:	Fri, 20 Nov 2015 15:22:48 +0300
From:	Denis Kirjanov <kda@...ux-powerpc.org>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	linuxppc-dev@...abs.org,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Anton Blanchard <anton@...ba.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc: tracing: don't trace hcalls on offline CPUs

On 11/3/15, Denis Kirjanov <kda@...ux-powerpc.org> wrote:
> On 11/3/15, Michael Ellerman <mpe@...erman.id.au> wrote:
>> On Thu, 2015-10-29 at 22:10 +0300, Denis Kirjanov wrote:
>>
>>> ./drmgr -c cpu -a -r gives the following warning:
>>>
>>> [ 2327.035563] RCU used illegally from offline CPU!
>>> rcu_scheduler_active
>>> = 1, debug_locks = 1
>>> [ 2327.035564] no locks held by swapper/12/0.
>>> [ 2327.035565] stack backtrace:
>>> [ 2327.035567] CPU: 12 PID: 0 Comm: swapper/12 Tainted: G S
>>> 4.3.0-rc3-00060-g353169a #5
>>> [ 2327.035568] Call Trace:
>>> [ 2327.035573] [c0000001d62578e0] [c0000000008977fc]
>>> .dump_stack+0x98/0xd4
>>> (unreliable)
>>> [ 2327.035577] [c0000001d6257960] [c000000000109bd8]
>>> .lockdep_rcu_suspicious+0x108/0x170
>>> [ 2327.035580] [c0000001d62579f0] [c00000000006a1d0]
>>> .__trace_hcall_exit+0x2b0/0x2c0
>>> [ 2327.035584] [c0000001d6257ab0] [c00000000006a2e8]
>>> plpar_hcall_norets_trace+0x70/0x8c
>>> [ 2327.035588] [c0000001d6257b20] [c000000000067a14]
>>> .icp_hv_set_cpu_priority+0x54/0xc0
>>> [ 2327.035592] [c0000001d6257ba0] [c000000000066c5c]
>>> .xics_teardown_cpu+0x5c/0xa0
>>> [ 2327.035595] [c0000001d6257c20] [c0000000000747ac]
>>> .pseries_mach_cpu_die+0x6c/0x320
>>> [ 2327.035598] [c0000001d6257cd0] [c0000000000439cc] .cpu_die+0x3c/0x60
>>> [ 2327.035602] [c0000001d6257d40] [c0000000000183d8]
>>> .arch_cpu_idle_dead+0x28/0x40
>>> [ 2327.035606] [c0000001d6257db0] [c0000000000ff1dc]
>>> .cpu_startup_entry+0x4fc/0x560
>>> [ 2327.035610] [c0000001d6257ed0] [c000000000043728]
>>> .start_secondary+0x328/0x360
>>> [ 2327.035614] [c0000001d6257f90] [c000000000008a6c]
>>> start_secondary_prolog+0x10/0x14
>>> [ 2327.035620] cpu 12 (hwid 12) Ready to die...
>>> [ 2327.144463] cpu 13 (hwid 13) Ready to die...
>>> [ 2327.294180] cpu 14 (hwid 14) Ready to die...
>>> [ 2327.403599] cpu 15 (hwid 15) Ready to die...
>>>
>>> Make the hypervisor tracepoints conditional by introducing
>>> TRACE_EVENT_FN_COND similar to TRACE_EVENT_FN
>>
>> We've fixed other cases like this with RCU_NONIDLE(), but I assume that
>> doesn't work here because we're actually offline?
>
> Yes, in this case we're moving the complete core offline through dlpar...
>

Hi Michael,
Could you pick this patch?

Thanks!

>>
>> cheers
>>
>>
>
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