Re: [PATCH v7 4/4] nmi_backtrace: generate one-line reports for idle cpus

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On Mon 2016-08-08 12:03:38, Chris Metcalf wrote:
> When doing an nmi backtrace of many cores, most of which are idle,
> the output is a little overwhelming and very uninformative.  Suppress
> messages for cpus that are idling when they are interrupted and just
> emit one line, "NMI backtrace for N skipped: idling at pc 0xNNN".
> 
> We do this by grouping all the cpuidle code together into a new
> .cpuidle.text section, and then checking the address of the
> interrupted PC to see if it lies within that section.
> 
> This commit suitably tags x86, arm64, and tile idle routines,
> and only adds in the minimal framework for other architectures.
> 
> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Tested-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
> ---
>  arch/alpha/kernel/vmlinux.lds.S      |  1 +
>  arch/arc/kernel/vmlinux.lds.S        |  1 +
>  arch/arm/kernel/vmlinux-xip.lds.S    |  1 +
>  arch/arm/kernel/vmlinux.lds.S        |  1 +
>  arch/arm64/kernel/vmlinux.lds.S      |  1 +
>  arch/arm64/mm/proc.S                 |  2 ++
>  arch/avr32/kernel/vmlinux.lds.S      |  1 +
>  arch/blackfin/kernel/vmlinux.lds.S   |  1 +
>  arch/c6x/kernel/vmlinux.lds.S        |  1 +
>  arch/cris/kernel/vmlinux.lds.S       |  1 +
>  arch/frv/kernel/vmlinux.lds.S        |  1 +
>  arch/h8300/kernel/vmlinux.lds.S      |  1 +
>  arch/hexagon/kernel/vmlinux.lds.S    |  1 +
>  arch/ia64/kernel/vmlinux.lds.S       |  1 +
>  arch/m32r/kernel/vmlinux.lds.S       |  1 +
>  arch/m68k/kernel/vmlinux-nommu.lds   |  1 +
>  arch/m68k/kernel/vmlinux-std.lds     |  1 +
>  arch/m68k/kernel/vmlinux-sun3.lds    |  1 +
>  arch/metag/kernel/vmlinux.lds.S      |  1 +
>  arch/microblaze/kernel/vmlinux.lds.S |  1 +
>  arch/mips/kernel/vmlinux.lds.S       |  1 +
>  arch/mn10300/kernel/vmlinux.lds.S    |  1 +
>  arch/nios2/kernel/vmlinux.lds.S      |  1 +
>  arch/openrisc/kernel/vmlinux.lds.S   |  1 +
>  arch/parisc/kernel/vmlinux.lds.S     |  1 +
>  arch/powerpc/kernel/vmlinux.lds.S    |  1 +
>  arch/s390/kernel/vmlinux.lds.S       |  1 +
>  arch/score/kernel/vmlinux.lds.S      |  1 +
>  arch/sh/kernel/vmlinux.lds.S         |  1 +
>  arch/sparc/kernel/vmlinux.lds.S      |  1 +
>  arch/tile/kernel/entry.S             |  2 +-
>  arch/tile/kernel/vmlinux.lds.S       |  1 +
>  arch/um/kernel/dyn.lds.S             |  1 +
>  arch/um/kernel/uml.lds.S             |  1 +
>  arch/unicore32/kernel/vmlinux.lds.S  |  1 +
>  arch/x86/kernel/acpi/cstate.c        |  2 +-
>  arch/x86/kernel/process.c            |  4 ++--
>  arch/x86/kernel/vmlinux.lds.S        |  1 +
>  arch/xtensa/kernel/vmlinux.lds.S     |  3 +++
>  drivers/acpi/processor_idle.c        |  5 +++--
>  drivers/cpuidle/driver.c             |  5 +++--
>  drivers/idle/intel_idle.c            |  4 ++--
>  include/asm-generic/vmlinux.lds.h    |  6 ++++++
>  include/linux/cpu.h                  |  5 +++++
>  kernel/sched/idle.c                  | 13 +++++++++++--
>  lib/nmi_backtrace.c                  | 16 +++++++++++-----
>  scripts/mod/modpost.c                |  2 +-
>  scripts/recordmcount.c               |  1 +
>  scripts/recordmcount.pl              |  1 +
>  49 files changed, 87 insertions(+), 18 deletions(-)
> 
> diff --git a/arch/alpha/kernel/vmlinux.lds.S b/arch/alpha/kernel/vmlinux.lds.S
> index 647b84c15382..cebecfb76fbf 100644
> --- a/arch/alpha/kernel/vmlinux.lds.S
> +++ b/arch/alpha/kernel/vmlinux.lds.S
> @@ -22,6 +22,7 @@ SECTIONS
>  		HEAD_TEXT
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		*(.fixup)
>  		*(.gnu.warning)
> diff --git a/arch/arc/kernel/vmlinux.lds.S b/arch/arc/kernel/vmlinux.lds.S
> index 894e696bddaa..65652160cfda 100644
> --- a/arch/arc/kernel/vmlinux.lds.S
> +++ b/arch/arc/kernel/vmlinux.lds.S
> @@ -97,6 +97,7 @@ SECTIONS
>  		_text = .;
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		*(.fixup)
> diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S
> index cba1ec899a69..7fa487ef7e2f 100644
> --- a/arch/arm/kernel/vmlinux-xip.lds.S
> +++ b/arch/arm/kernel/vmlinux-xip.lds.S
> @@ -98,6 +98,7 @@ SECTIONS
>  			IRQENTRY_TEXT
>  			TEXT_TEXT
>  			SCHED_TEXT
> +			CPUIDLE_TEXT
>  			LOCK_TEXT
>  			KPROBES_TEXT
>  			*(.gnu.warning)
> diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
> index d24e5dd2aa7a..f7f55df0bf7b 100644
> --- a/arch/arm/kernel/vmlinux.lds.S
> +++ b/arch/arm/kernel/vmlinux.lds.S
> @@ -111,6 +111,7 @@ SECTIONS
>  			SOFTIRQENTRY_TEXT
>  			TEXT_TEXT
>  			SCHED_TEXT
> +			CPUIDLE_TEXT
>  			LOCK_TEXT
>  			HYPERVISOR_TEXT
>  			KPROBES_TEXT
> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> index 659963d40bb4..fe7f93b7b11b 100644
> --- a/arch/arm64/kernel/vmlinux.lds.S
> +++ b/arch/arm64/kernel/vmlinux.lds.S
> @@ -122,6 +122,7 @@ SECTIONS
>  			ENTRY_TEXT
>  			TEXT_TEXT
>  			SCHED_TEXT
> +			CPUIDLE_TEXT
>  			LOCK_TEXT
>  			KPROBES_TEXT
>  			HYPERVISOR_TEXT
> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index 5bb61de23201..64f088ca3192 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -48,11 +48,13 @@
>   *
>   *	Idle the processor (wait for interrupt).
>   */
> +	.pushsection ".cpuidle.text","ax"
>  ENTRY(cpu_do_idle)
>  	dsb	sy				// WFI may enter a low-power mode
>  	wfi
>  	ret
>  ENDPROC(cpu_do_idle)
> +	.popsection
>  
>  #ifdef CONFIG_CPU_PM
>  /**
> diff --git a/arch/avr32/kernel/vmlinux.lds.S b/arch/avr32/kernel/vmlinux.lds.S
> index a4589176bed5..17f2730eb497 100644
> --- a/arch/avr32/kernel/vmlinux.lds.S
> +++ b/arch/avr32/kernel/vmlinux.lds.S
> @@ -52,6 +52,7 @@ SECTIONS
>  		KPROBES_TEXT
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		*(.fixup)
>  		*(.gnu.warning)
> diff --git a/arch/blackfin/kernel/vmlinux.lds.S b/arch/blackfin/kernel/vmlinux.lds.S
> index d920b959ff3a..68069a120055 100644
> --- a/arch/blackfin/kernel/vmlinux.lds.S
> +++ b/arch/blackfin/kernel/vmlinux.lds.S
> @@ -33,6 +33,7 @@ SECTIONS
>  #ifndef CONFIG_SCHEDULE_L1
>  		SCHED_TEXT
>  #endif
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		IRQENTRY_TEXT
>  		SOFTIRQENTRY_TEXT
> diff --git a/arch/c6x/kernel/vmlinux.lds.S b/arch/c6x/kernel/vmlinux.lds.S
> index 50bc10f97bcb..a1a5c166bc9b 100644
> --- a/arch/c6x/kernel/vmlinux.lds.S
> +++ b/arch/c6x/kernel/vmlinux.lds.S
> @@ -70,6 +70,7 @@ SECTIONS
>  		_stext = .;
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		IRQENTRY_TEXT
>  		SOFTIRQENTRY_TEXT
> diff --git a/arch/cris/kernel/vmlinux.lds.S b/arch/cris/kernel/vmlinux.lds.S
> index 7552c2557506..979586261520 100644
> --- a/arch/cris/kernel/vmlinux.lds.S
> +++ b/arch/cris/kernel/vmlinux.lds.S
> @@ -43,6 +43,7 @@ SECTIONS
>  		HEAD_TEXT
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		*(.fixup)
>  		*(.text.__*)
> diff --git a/arch/frv/kernel/vmlinux.lds.S b/arch/frv/kernel/vmlinux.lds.S
> index 7e958d829ec9..aa6e573d57da 100644
> --- a/arch/frv/kernel/vmlinux.lds.S
> +++ b/arch/frv/kernel/vmlinux.lds.S
> @@ -63,6 +63,7 @@ SECTIONS
>  	*(.text..tlbmiss)
>  	TEXT_TEXT
>  	SCHED_TEXT
> +	CPUIDLE_TEXT
>  	LOCK_TEXT
>  #ifdef CONFIG_DEBUG_INFO
>  	INIT_TEXT
> diff --git a/arch/h8300/kernel/vmlinux.lds.S b/arch/h8300/kernel/vmlinux.lds.S
> index cb5dfb02c88d..7f11da1b895e 100644
> --- a/arch/h8300/kernel/vmlinux.lds.S
> +++ b/arch/h8300/kernel/vmlinux.lds.S
> @@ -29,6 +29,7 @@ SECTIONS
>  	_stext = . ;
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  #if defined(CONFIG_ROMKERNEL)
>  		*(.int_redirect)
> diff --git a/arch/hexagon/kernel/vmlinux.lds.S b/arch/hexagon/kernel/vmlinux.lds.S
> index 5f268c1071b3..ec87e67feb19 100644
> --- a/arch/hexagon/kernel/vmlinux.lds.S
> +++ b/arch/hexagon/kernel/vmlinux.lds.S
> @@ -50,6 +50,7 @@ SECTIONS
>  		_text = .;
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		*(.fixup)
> diff --git a/arch/ia64/kernel/vmlinux.lds.S b/arch/ia64/kernel/vmlinux.lds.S
> index dc506b05ffbd..f89d20c97412 100644
> --- a/arch/ia64/kernel/vmlinux.lds.S
> +++ b/arch/ia64/kernel/vmlinux.lds.S
> @@ -46,6 +46,7 @@ SECTIONS {
>  		__end_ivt_text = .;
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		*(.gnu.linkonce.t*)
> diff --git a/arch/m32r/kernel/vmlinux.lds.S b/arch/m32r/kernel/vmlinux.lds.S
> index 018e4a711d79..ad1fe56455aa 100644
> --- a/arch/m32r/kernel/vmlinux.lds.S
> +++ b/arch/m32r/kernel/vmlinux.lds.S
> @@ -31,6 +31,7 @@ SECTIONS
>  	HEAD_TEXT
>  	TEXT_TEXT
>  	SCHED_TEXT
> +	CPUIDLE_TEXT
>  	LOCK_TEXT
>  	*(.fixup)
>  	*(.gnu.warning)
> diff --git a/arch/m68k/kernel/vmlinux-nommu.lds b/arch/m68k/kernel/vmlinux-nommu.lds
> index 06a763f49fd3..d2c8abf1c8c4 100644
> --- a/arch/m68k/kernel/vmlinux-nommu.lds
> +++ b/arch/m68k/kernel/vmlinux-nommu.lds
> @@ -45,6 +45,7 @@ SECTIONS {
>  		HEAD_TEXT
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		*(.fixup)
>  		. = ALIGN(16);
> diff --git a/arch/m68k/kernel/vmlinux-std.lds b/arch/m68k/kernel/vmlinux-std.lds
> index d0993594f558..5b5ce1e4d1ed 100644
> --- a/arch/m68k/kernel/vmlinux-std.lds
> +++ b/arch/m68k/kernel/vmlinux-std.lds
> @@ -16,6 +16,7 @@ SECTIONS
>  	HEAD_TEXT
>  	TEXT_TEXT
>  	SCHED_TEXT
> +	CPUIDLE_TEXT
>  	LOCK_TEXT
>  	*(.fixup)
>  	*(.gnu.warning)
> diff --git a/arch/m68k/kernel/vmlinux-sun3.lds b/arch/m68k/kernel/vmlinux-sun3.lds
> index 8080469ee6c1..fe5ea1974b16 100644
> --- a/arch/m68k/kernel/vmlinux-sun3.lds
> +++ b/arch/m68k/kernel/vmlinux-sun3.lds
> @@ -16,6 +16,7 @@ SECTIONS
>  	HEAD_TEXT
>  	TEXT_TEXT
>  	SCHED_TEXT
> +	CPUIDLE_TEXT
>  	LOCK_TEXT
>  	*(.fixup)
>  	*(.gnu.warning)
> diff --git a/arch/metag/kernel/vmlinux.lds.S b/arch/metag/kernel/vmlinux.lds.S
> index 150ace92c7ad..e6c700eaf207 100644
> --- a/arch/metag/kernel/vmlinux.lds.S
> +++ b/arch/metag/kernel/vmlinux.lds.S
> @@ -21,6 +21,7 @@ SECTIONS
>    .text : {
>  	TEXT_TEXT
>  	SCHED_TEXT
> +	CPUIDLE_TEXT
>  	LOCK_TEXT
>  	KPROBES_TEXT
>  	IRQENTRY_TEXT
> diff --git a/arch/microblaze/kernel/vmlinux.lds.S b/arch/microblaze/kernel/vmlinux.lds.S
> index 0a47f0410554..289d0e7f3e3a 100644
> --- a/arch/microblaze/kernel/vmlinux.lds.S
> +++ b/arch/microblaze/kernel/vmlinux.lds.S
> @@ -33,6 +33,7 @@ SECTIONS {
>  		EXIT_TEXT
>  		EXIT_CALL
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		IRQENTRY_TEXT
> diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S
> index a82c178d0bb9..d5de67591735 100644
> --- a/arch/mips/kernel/vmlinux.lds.S
> +++ b/arch/mips/kernel/vmlinux.lds.S
> @@ -55,6 +55,7 @@ SECTIONS
>  	.text : {
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		IRQENTRY_TEXT
> diff --git a/arch/mn10300/kernel/vmlinux.lds.S b/arch/mn10300/kernel/vmlinux.lds.S
> index 13c4814c29f8..2d5f1c3f1afb 100644
> --- a/arch/mn10300/kernel/vmlinux.lds.S
> +++ b/arch/mn10300/kernel/vmlinux.lds.S
> @@ -30,6 +30,7 @@ SECTIONS
>  	HEAD_TEXT
>  	TEXT_TEXT
>  	SCHED_TEXT
> +	CPUIDLE_TEXT
>  	LOCK_TEXT
>  	KPROBES_TEXT
>  	*(.fixup)
> diff --git a/arch/nios2/kernel/vmlinux.lds.S b/arch/nios2/kernel/vmlinux.lds.S
> index e23e89539967..6a8045bb1a77 100644
> --- a/arch/nios2/kernel/vmlinux.lds.S
> +++ b/arch/nios2/kernel/vmlinux.lds.S
> @@ -37,6 +37,7 @@ SECTIONS
>  	.text : {
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		IRQENTRY_TEXT
>  		SOFTIRQENTRY_TEXT
> diff --git a/arch/openrisc/kernel/vmlinux.lds.S b/arch/openrisc/kernel/vmlinux.lds.S
> index d936de4c07ca..d68b9ede8423 100644
> --- a/arch/openrisc/kernel/vmlinux.lds.S
> +++ b/arch/openrisc/kernel/vmlinux.lds.S
> @@ -47,6 +47,7 @@ SECTIONS
>            _stext = .;
>  	  TEXT_TEXT
>  	  SCHED_TEXT
> +	  CPUIDLE_TEXT
>  	  LOCK_TEXT
>  	  KPROBES_TEXT
>  	  IRQENTRY_TEXT
> diff --git a/arch/parisc/kernel/vmlinux.lds.S b/arch/parisc/kernel/vmlinux.lds.S
> index f3ead0b6ce46..9ec8ec075dae 100644
> --- a/arch/parisc/kernel/vmlinux.lds.S
> +++ b/arch/parisc/kernel/vmlinux.lds.S
> @@ -69,6 +69,7 @@ SECTIONS
>  	.text ALIGN(PAGE_SIZE) : {
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		IRQENTRY_TEXT
> diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
> index b5fba689fca6..7ed59f0d947f 100644
> --- a/arch/powerpc/kernel/vmlinux.lds.S
> +++ b/arch/powerpc/kernel/vmlinux.lds.S
> @@ -52,6 +52,7 @@ SECTIONS
>  		/* careful! __ftr_alt_* sections need to be close to .text */
>  		*(.text .fixup __ftr_alt_* .ref.text)
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		IRQENTRY_TEXT
> diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S
> index 429bfd111961..000e6e91f6a0 100644
> --- a/arch/s390/kernel/vmlinux.lds.S
> +++ b/arch/s390/kernel/vmlinux.lds.S
> @@ -35,6 +35,7 @@ SECTIONS
>  		HEAD_TEXT
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		IRQENTRY_TEXT
> diff --git a/arch/score/kernel/vmlinux.lds.S b/arch/score/kernel/vmlinux.lds.S
> index 7274b5c4287e..4117890b1db1 100644
> --- a/arch/score/kernel/vmlinux.lds.S
> +++ b/arch/score/kernel/vmlinux.lds.S
> @@ -40,6 +40,7 @@ SECTIONS
>  		_text = .;	/* Text and read-only data */
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		*(.text.*)
> diff --git a/arch/sh/kernel/vmlinux.lds.S b/arch/sh/kernel/vmlinux.lds.S
> index 235a4101999f..5b9a3cc90c58 100644
> --- a/arch/sh/kernel/vmlinux.lds.S
> +++ b/arch/sh/kernel/vmlinux.lds.S
> @@ -36,6 +36,7 @@ SECTIONS
>  		TEXT_TEXT
>  		EXTRA_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		IRQENTRY_TEXT
> diff --git a/arch/sparc/kernel/vmlinux.lds.S b/arch/sparc/kernel/vmlinux.lds.S
> index d79b3b734245..572db686f845 100644
> --- a/arch/sparc/kernel/vmlinux.lds.S
> +++ b/arch/sparc/kernel/vmlinux.lds.S
> @@ -49,6 +49,7 @@ SECTIONS
>  		HEAD_TEXT
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		IRQENTRY_TEXT
> diff --git a/arch/tile/kernel/entry.S b/arch/tile/kernel/entry.S
> index 670a3569450f..101de132e363 100644
> --- a/arch/tile/kernel/entry.S
> +++ b/arch/tile/kernel/entry.S
> @@ -50,7 +50,7 @@ STD_ENTRY(smp_nap)
>   * When interrupted at _cpu_idle_nap, we bump the PC forward 8, and
>   * as a result return to the function that called _cpu_idle().
>   */
> -STD_ENTRY(_cpu_idle)
> +STD_ENTRY_SECTION(_cpu_idle, .cpuidle.text)
>  	movei r1, 1
>  	IRQ_ENABLE_LOAD(r2, r3)
>  	mtspr INTERRUPT_CRITICAL_SECTION, r1
> diff --git a/arch/tile/kernel/vmlinux.lds.S b/arch/tile/kernel/vmlinux.lds.S
> index 9d449caf8910..e1baf094fba4 100644
> --- a/arch/tile/kernel/vmlinux.lds.S
> +++ b/arch/tile/kernel/vmlinux.lds.S
> @@ -42,6 +42,7 @@ SECTIONS
>    .text : AT (ADDR(.text) - LOAD_OFFSET) {
>      HEAD_TEXT
>      SCHED_TEXT
> +    CPUIDLE_TEXT
>      LOCK_TEXT
>      KPROBES_TEXT
>      IRQENTRY_TEXT
> diff --git a/arch/um/kernel/dyn.lds.S b/arch/um/kernel/dyn.lds.S
> index adde088aeeff..4fdbcf958cd5 100644
> --- a/arch/um/kernel/dyn.lds.S
> +++ b/arch/um/kernel/dyn.lds.S
> @@ -68,6 +68,7 @@ SECTIONS
>      _stext = .;
>      TEXT_TEXT
>      SCHED_TEXT
> +    CPUIDLE_TEXT
>      LOCK_TEXT
>      *(.fixup)
>      *(.stub .text.* .gnu.linkonce.t.*)
> diff --git a/arch/um/kernel/uml.lds.S b/arch/um/kernel/uml.lds.S
> index 6899195602b7..1840f55ed042 100644
> --- a/arch/um/kernel/uml.lds.S
> +++ b/arch/um/kernel/uml.lds.S
> @@ -28,6 +28,7 @@ SECTIONS
>      _stext = .;
>      TEXT_TEXT
>      SCHED_TEXT
> +    CPUIDLE_TEXT
>      LOCK_TEXT
>      *(.fixup)
>      /* .gnu.warning sections are handled specially by elf32.em.  */
> diff --git a/arch/unicore32/kernel/vmlinux.lds.S b/arch/unicore32/kernel/vmlinux.lds.S
> index 77e407e49a63..56e788e8ee83 100644
> --- a/arch/unicore32/kernel/vmlinux.lds.S
> +++ b/arch/unicore32/kernel/vmlinux.lds.S
> @@ -37,6 +37,7 @@ SECTIONS
>  	.text : {		/* Real text segment */
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  
>  		*(.fixup)
> diff --git a/arch/x86/kernel/acpi/cstate.c b/arch/x86/kernel/acpi/cstate.c
> index bdfad642123f..af15f4444330 100644
> --- a/arch/x86/kernel/acpi/cstate.c
> +++ b/arch/x86/kernel/acpi/cstate.c
> @@ -152,7 +152,7 @@ int acpi_processor_ffh_cstate_probe(unsigned int cpu,
>  }
>  EXPORT_SYMBOL_GPL(acpi_processor_ffh_cstate_probe);
>  
> -void acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx)
> +void __cpuidle acpi_processor_ffh_cstate_enter(struct acpi_processor_cx *cx)
>  {
>  	unsigned int cpu = smp_processor_id();
>  	struct cstate_entry *percpu_entry;
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index 62c0b0ea2ce4..c400e30831dc 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -301,7 +301,7 @@ void arch_cpu_idle(void)
>  /*
>   * We use this if we don't have any better idle routine..
>   */
> -void default_idle(void)
> +void __cpuidle default_idle(void)
>  {
>  	trace_cpu_idle_rcuidle(1, smp_processor_id());
>  	safe_halt();
> @@ -416,7 +416,7 @@ static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
>   * with interrupts enabled and no flags, which is backwards compatible with the
>   * original MWAIT implementation.
>   */
> -static void mwait_idle(void)
> +static __cpuidle void mwait_idle(void)
>  {
>  	if (!current_set_polling_and_test()) {
>  		trace_cpu_idle_rcuidle(1, smp_processor_id());
> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
> index 9297a002d8e5..dbf67f64d5ec 100644
> --- a/arch/x86/kernel/vmlinux.lds.S
> +++ b/arch/x86/kernel/vmlinux.lds.S
> @@ -97,6 +97,7 @@ SECTIONS
>  		_stext = .;
>  		TEXT_TEXT
>  		SCHED_TEXT
> +		CPUIDLE_TEXT
>  		LOCK_TEXT
>  		KPROBES_TEXT
>  		ENTRY_TEXT
> diff --git a/arch/xtensa/kernel/vmlinux.lds.S b/arch/xtensa/kernel/vmlinux.lds.S
> index c417cbe4ec87..18a174c7fb87 100644
> --- a/arch/xtensa/kernel/vmlinux.lds.S
> +++ b/arch/xtensa/kernel/vmlinux.lds.S
> @@ -93,6 +93,9 @@ SECTIONS
>      VMLINUX_SYMBOL(__sched_text_start) = .;
>      *(.sched.literal .sched.text)
>      VMLINUX_SYMBOL(__sched_text_end) = .;
> +    VMLINUX_SYMBOL(__cpuidle_text_start) = .;
> +    *(.cpuidle.literal .cpuidle.text)
> +    VMLINUX_SYMBOL(__cpuidle_text_end) = .;
>      VMLINUX_SYMBOL(__lock_text_start) = .;
>      *(.spinlock.literal .spinlock.text)
>      VMLINUX_SYMBOL(__lock_text_end) = .;
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index cea52528aa18..2237d3f24f0e 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -31,6 +31,7 @@
>  #include <linux/sched.h>       /* need_resched() */
>  #include <linux/tick.h>
>  #include <linux/cpuidle.h>
> +#include <linux/cpu.h>
>  #include <acpi/processor.h>
>  
>  /*
> @@ -115,7 +116,7 @@ static const struct dmi_system_id processor_power_dmi_table[] = {
>   * Callers should disable interrupts before the call and enable
>   * interrupts after return.
>   */
> -static void acpi_safe_halt(void)
> +static void __cpuidle acpi_safe_halt(void)
>  {
>  	if (!tif_need_resched()) {
>  		safe_halt();
> @@ -645,7 +646,7 @@ static int acpi_idle_bm_check(void)
>   *
>   * Caller disables interrupt before call and enables interrupt after return.
>   */
> -static void acpi_idle_do_entry(struct acpi_processor_cx *cx)
> +static void __cpuidle acpi_idle_do_entry(struct acpi_processor_cx *cx)
>  {
>  	if (cx->entry_method == ACPI_CSTATE_FFH) {
>  		/* Call into architectural FFH based C-state */
> diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
> index 389ade4572be..ab264d393233 100644
> --- a/drivers/cpuidle/driver.c
> +++ b/drivers/cpuidle/driver.c
> @@ -14,6 +14,7 @@
>  #include <linux/cpuidle.h>
>  #include <linux/cpumask.h>
>  #include <linux/tick.h>
> +#include <linux/cpu.h>
>  
>  #include "cpuidle.h"
>  
> @@ -178,8 +179,8 @@ static void __cpuidle_driver_init(struct cpuidle_driver *drv)
>  }
>  
>  #ifdef CONFIG_ARCH_HAS_CPU_RELAX
> -static int poll_idle(struct cpuidle_device *dev,
> -		struct cpuidle_driver *drv, int index)
> +static int __cpuidle poll_idle(struct cpuidle_device *dev,
> +			       struct cpuidle_driver *drv, int index)
>  {
>  	local_irq_enable();
>  	if (!current_set_polling_and_test()) {
> diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
> index 67ec58f9ef99..4466a2f969d7 100644
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -863,8 +863,8 @@ static struct cpuidle_state dnv_cstates[] = {
>   *
>   * Must be called under local_irq_disable().
>   */
> -static int intel_idle(struct cpuidle_device *dev,
> -		struct cpuidle_driver *drv, int index)
> +static __cpuidle int intel_idle(struct cpuidle_device *dev,
> +				struct cpuidle_driver *drv, int index)
>  {
>  	unsigned long ecx = 1; /* break on interrupt flag */
>  	struct cpuidle_state *state = &drv->states[index];
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index 24563970ff7b..3e42bcdd014b 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -454,6 +454,12 @@
>  		*(.spinlock.text)					\
>  		VMLINUX_SYMBOL(__lock_text_end) = .;
>  
> +#define CPUIDLE_TEXT							\
> +		ALIGN_FUNCTION();					\
> +		VMLINUX_SYMBOL(__cpuidle_text_start) = .;		\
> +		*(.cpuidle.text)					\
> +		VMLINUX_SYMBOL(__cpuidle_text_end) = .;
> +
>  #define KPROBES_TEXT							\
>  		ALIGN_FUNCTION();					\
>  		VMLINUX_SYMBOL(__kprobes_text_start) = .;		\
> diff --git a/include/linux/cpu.h b/include/linux/cpu.h
> index 797d9c8e9a1b..6babfa6db9d9 100644
> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -239,6 +239,11 @@ void cpu_startup_entry(enum cpuhp_state state);
>  
>  void cpu_idle_poll_ctrl(bool enable);
>  
> +/* Attach to any functions which should be considered cpuidle. */
> +#define __cpuidle	__attribute__((__section__(".cpuidle.text")))
> +
> +bool cpu_in_idle(unsigned long pc);
> +
>  void arch_cpu_idle(void);
>  void arch_cpu_idle_prepare(void);
>  void arch_cpu_idle_enter(void);
> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index 9fb873cfc75c..1d8718d5300d 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -16,6 +16,9 @@
>  
>  #include "sched.h"
>  
> +/* Linker adds these: start and end of __cpuidle functions */
> +extern char __cpuidle_text_start[], __cpuidle_text_end[];
> +
>  /**
>   * sched_idle_set_state - Record idle state for the current CPU.
>   * @idle_state: State to record.
> @@ -53,7 +56,7 @@ static int __init cpu_idle_nopoll_setup(char *__unused)
>  __setup("hlt", cpu_idle_nopoll_setup);
>  #endif
>  
> -static inline int cpu_idle_poll(void)
> +static noinline int __cpuidle cpu_idle_poll(void)
>  {
>  	rcu_idle_enter();
>  	trace_cpu_idle_rcuidle(0, smp_processor_id());
> @@ -84,7 +87,7 @@ void __weak arch_cpu_idle(void)
>   *
>   * To use when the cpuidle framework cannot be used.
>   */
> -void default_idle_call(void)
> +void __cpuidle default_idle_call(void)
>  {
>  	if (current_clr_polling_and_test()) {
>  		local_irq_enable();
> @@ -271,6 +274,12 @@ static void cpu_idle_loop(void)
>  	}
>  }
>  
> +bool cpu_in_idle(unsigned long pc)
> +{
> +	return pc >= (unsigned long)__cpuidle_text_start &&
> +		pc < (unsigned long)__cpuidle_text_end;
> +}
> +
>  void cpu_startup_entry(enum cpuhp_state state)
>  {
>  	/*
> diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c
> index 2933f0680174..de0d406e95cc 100644
> --- a/lib/nmi_backtrace.c
> +++ b/lib/nmi_backtrace.c
> @@ -16,6 +16,7 @@
>  #include <linux/delay.h>
>  #include <linux/kprobes.h>
>  #include <linux/nmi.h>
> +#include <linux/cpu.h>
>  
>  #ifdef arch_trigger_cpumask_backtrace
>  /* For reliability, we're prepared to waste bits here. */
> @@ -87,11 +88,16 @@ bool nmi_cpu_backtrace(struct pt_regs *regs)
>  	int cpu = smp_processor_id();
>  
>  	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
> -		pr_warn("NMI backtrace for cpu %d\n", cpu);
> -		if (regs)
> -			show_regs(regs);
> -		else
> -			dump_stack();
> +		if (regs && cpu_in_idle(instruction_pointer(regs))) {
> +			pr_warn("NMI backtrace for cpu %d skipped: idling at pc %#lx\n",
> +				cpu, instruction_pointer(regs));

Hmm, I do not see this message even though the CPU is in the idle state:

[ 7918.884535] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 4.8.0-rc1-4-default+ #3088
[ 7918.884538] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
[ 7918.884539] task: ffff88013a594380 task.stack: ffff88013a598000
[ 7918.884541] RIP: 0010:[<ffffffff81050bc6>]  [<ffffffff81050bc6>] native_safe_halt+0x6/0x10
[ 7918.884543] RSP: 0018:ffff88013a59bea8  EFLAGS: 00000206
[ 7918.884544] RAX: ffff88013a594380 RBX: 0000000000000003 RCX: 0000000000000000
[ 7918.884546] RDX: ffff88013a594380 RSI: 0000000000000001 RDI: ffff88013a594380
[ 7918.884548] RBP: ffff88013a59bea8 R08: 0000000000000000 R09: 0000000000000000
[ 7918.884550] R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000003
[ 7918.884551] R13: 0000000000000000 R14: ffff88013a598000 R15: ffff88013a598000
[ 7918.884553] FS:  0000000000000000(0000) GS:ffff88013fd80000(0000) knlGS:0000000000000000
[ 7918.884554] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 7918.884556] CR2: 00007f8afc65e000 CR3: 00000001383b8000 CR4: 00000000000006e0
[ 7918.884557] Stack:
[ 7918.884559]  ffff88013a59bec8 ffffffff819573d3 0000000000000003 0000000000000000
[ 7918.884561]  ffff88013a59bed8 ffffffff8102628f ffff88013a59bee8 ffffffff819579ea
[ 7918.884562]  ffff88013a59bf30 ffffffff810bfe1a ffff88013a598000 ffff88013a598000
[ 7918.884563] Call Trace:
[ 7918.884565]  [<ffffffff819573d3>] default_idle+0x23/0x170
[ 7918.884566]  [<ffffffff8102628f>] arch_cpu_idle+0xf/0x20
[ 7918.884568]  [<ffffffff819579ea>] default_idle_call+0x2a/0x50
[ 7918.884570]  [<ffffffff810bfe1a>] cpu_startup_entry+0x16a/0x260
[ 7918.884571]  [<ffffffff8103faf6>] start_secondary+0xf6/0x100
[ 7918.884573] Code: 00 00 00 00 00 55 48 89 e5 fa 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb 5d c3 66 0f 1f 84 00 00 00 00 00 55 48 89 e5 fb f4 <5d> c3 0f 1f 84 00 00 00 00 00 55
 48 89 e5 f4 5d c3 66 0f 1f 84 

Note that I test it in a virtual machine using qemu.

The strange thing is that I do not see .cpuidle.text section in
the vmlinux binary. But it is possible that I have misunderstood
the concept.

Best Regards,
Petr
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