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

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Message-ID: <20151207155224.2a8d71dd@gandalf.local.home>
Date:	Mon, 7 Dec 2015 15:52:24 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Denis Kirjanov <kda@...ux-powerpc.org>
Cc:	Michael Ellerman <mpe@...erman.id.au>, linuxppc-dev@...abs.org,
	linux-kernel@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH 2/2] powerpc: tracing: don't trace hcalls on offline
 CPUs


I can take this series through my tree, but I need a acked-by from a
PPC maintainer for this patch.

-- Steve


On Tue, 24 Nov 2015 21:23:39 +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>
> ---
>  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..3dc5803 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(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(smp_processor_id())),
> +
>  	TP_STRUCT__entry(
>  		__field(unsigned long, opcode)
>  		__field(unsigned long, retval)

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