linux-kernel - Re: [PATCH v3 2/2] powerpc: tracing: don't trace hcalls on offline CPUs

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Date:	Tue, 12 Jan 2016 13:53:38 +0300
From:	Denis Kirjanov <kda@...ux-powerpc.org>
To:	Michael Ellerman <michael@...erman.id.au>
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH v3 2/2] powerpc: tracing: don't trace hcalls on offline CPUs

On 12/23/15, Steven Rostedt <rostedt@...dmis.org> wrote:
> On Mon, 14 Dec 2015 23:18:06 +0300
> Denis Kirjanov <kda@...ux-powerpc.org> 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 using TRACE_EVENT_FN_COND
>>
>> Signed-off-by: Denis Kirjanov <kda@...ux-powerpc.org>
>
> I applied the first patch, but I need Acks from the powerpc maintainers
> to take this one.
>

Hi Michael,

Could you please put your ack to the second patch.

Thanks!

> -- Steve
>
>
>>
>> v2 changes:
>>  - Use raw_smp_processor_id as suggested by BenH
>>  since since hcalls can be called from preemptable sections
>>
>> v3 changes:
>>  - Fix the subject line
>> ---
>>  arch/powerpc/include/asm/trace.h | 8 ++++++--
>>  1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/trace.h
>> b/arch/powerpc/include/asm/trace.h
>> index 8e86b48..32e36b1 100644
>> --- a/arch/powerpc/include/asm/trace.h
>> +++ b/arch/powerpc/include/asm/trace.h
>> @@ -57,12 +57,14 @@ DEFINE_EVENT(ppc64_interrupt_class,
>> timer_interrupt_exit,
>>  extern void hcall_tracepoint_regfunc(void);
>>  extern void hcall_tracepoint_unregfunc(void);
>>
>> -TRACE_EVENT_FN(hcall_entry,
>> +TRACE_EVENT_FN_COND(hcall_entry,
>>
>>  	TP_PROTO(unsigned long opcode, unsigned long *args),
>>
>>  	TP_ARGS(opcode, args),
>>
>> +	TP_CONDITION(cpu_online(raw_smp_processor_id())),
>> +
>>  	TP_STRUCT__entry(
>>  		__field(unsigned long, opcode)
>>  	),
>> @@ -76,13 +78,15 @@ TRACE_EVENT_FN(hcall_entry,
>>  	hcall_tracepoint_regfunc, hcall_tracepoint_unregfunc
>>  );
>>
>> -TRACE_EVENT_FN(hcall_exit,
>> +TRACE_EVENT_FN_COND(hcall_exit,
>>
>>  	TP_PROTO(unsigned long opcode, unsigned long retval,
>>  		unsigned long *retbuf),
>>
>>  	TP_ARGS(opcode, retval, retbuf),
>>
>> +	TP_CONDITION(cpu_online(raw_smp_processor_id())),
>> +
>>  	TP_STRUCT__entry(
>>  		__field(unsigned long, opcode)
>>  		__field(unsigned long, retval)
>
>