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eddc0e922a
linux/arch/x86/kernel
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Seiji Aguchi eddc0e922a x86, trace: Introduce entering/exiting_irq() 
When implementing tracepoints in interrupt handers, if the tracepoints are
simply added in the performance sensitive path of interrupt handers,
it may cause potential performance problem due to the time penalty.

To solve the problem, an idea is to prepare non-trace/trace irq handers and
switch their IDTs at the enabling/disabling time.

So, let's introduce entering_irq()/exiting_irq() for pre/post-
processing of each irq handler.

A way to use them is as follows.

Non-trace irq handler:
smp_irq_handler()
{
	entering_irq();		/* pre-processing of this handler */
	__smp_irq_handler();	/*
				 * common logic between non-trace and trace handlers
				 * in a vector.
				 */
	exiting_irq();		/* post-processing of this handler */

}

Trace irq_handler:
smp_trace_irq_handler()
{
	entering_irq();		/* pre-processing of this handler */
	trace_irq_entry();	/* tracepoint for irq entry */
	__smp_irq_handler();	/*
				 * common logic between non-trace and trace handlers
				 * in a vector.
				 */
	trace_irq_exit();	/* tracepoint for irq exit */
	exiting_irq();		/* post-processing of this handler */

}

If tracepoints can place outside entering_irq()/exiting_irq() as follows,
it looks cleaner.

smp_trace_irq_handler()
{
	trace_irq_entry();
	smp_irq_handler();
	trace_irq_exit();
}

But it doesn't work.
The problem is with irq_enter/exit() being called. They must be called before
trace_irq_enter/exit(),  because of the rcu_irq_enter() must be called before
any tracepoints are used, as tracepoints use  rcu to synchronize.

As a possible alternative, we may be able to call irq_enter() first as follows
if irq_enter() can nest.

smp_trace_irq_hander()
{
	irq_entry();
	trace_irq_entry();
	smp_irq_handler();
	trace_irq_exit();
	irq_exit();
}

But it doesn't work, either.
If irq_enter() is nested, it may have a time penalty because it has to check if it
was already called or not. The time penalty is not desired in performance sensitive
paths even if it is tiny.

Signed-off-by: Seiji Aguchi <seiji.aguchi@hds.com>
Link: http://lkml.kernel.org/r/51C3238D.9040706@hds.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
2013-06-20 22:25:01 -07:00
..
acpi Merge branch 'x86-paravirt-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-04-30 08:41:21 -07:00
apic x86, trace: Introduce entering/exiting_irq() 2013-06-20 22:25:01 -07:00
cpu x86, trace: Introduce entering/exiting_irq() 2013-06-20 22:25:01 -07:00
kprobes kprobes/x86: Just return error for sanity check failure instead of using BUG_ON 2013-04-08 17:28:34 +02:00
.gitignore
alternative.c x86, cpu: Expand cpufeature facility to include cpu bugs 2013-04-02 10:12:52 -07:00
amd_gart_64.c x86, mm: use pfn_range_is_mapped() with gart 2012-11-17 11:59:10 -08:00
amd_nb.c Merge branch 'x86-ras-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-04-30 08:42:45 -07:00
apb_timer.c Merge branch 'x86-platform-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-19 20:11:07 -08:00
aperture_64.c x86/mm/gart: Drop unnecessary check 2013-04-16 10:54:40 +02:00
apm_32.c cpuidle: remove en_core_tk_irqen flag 2013-04-23 13:45:22 +02:00
asm-offsets_32.c x86, gdt, hibernate: Store/load GDT for hibernate path. 2013-05-02 11:27:35 -07:00
asm-offsets_64.c x86, gdt, hibernate: Store/load GDT for hibernate path. 2013-05-02 11:27:35 -07:00
asm-offsets.c x86, um/x86: switch to generic sys_execve and kernel_execve 2012-09-30 22:53:32 -04:00
audit_64.c
bootflag.c
check.c x86: kernel/check.c simple_strtoul cleanup 2012-05-15 15:36:41 -07:00
cpuid.c new helper: file_inode(file) 2013-02-22 23:31:31 -05:00
crash_dump_32.c
crash_dump_64.c
crash.c x86/kexec: crash_vmclear_local_vmcss needs __rcu 2012-12-11 19:55:23 -02:00
devicetree.c x86: dt: Use linear irq domain for ioapic(s) 2012-08-21 22:16:57 +02:00
doublefault_32.c x86, xen, gdt: Remove the pvops variant of store_gdt. 2013-04-11 15:40:38 -07:00
dumpstack_32.c dump_stack: unify debug information printed by show_regs() 2013-04-30 17:04:02 -07:00
dumpstack_64.c dump_stack: unify debug information printed by show_regs() 2013-04-30 17:04:02 -07:00
dumpstack.c dump_stack: consolidate dump_stack() implementations and unify their behaviors 2013-04-30 17:04:02 -07:00
e820.c x86, mm: Let "memmap=" take more entries one time 2012-11-17 11:59:51 -08:00
early_printk.c early_printk: consolidate random copies of identical code 2013-04-29 18:28:13 -07:00
early-quirks.c iommu/vt-d: add quirk for broken interrupt remapping on 55XX chipsets 2013-04-18 17:00:47 +02:00
entry_32.S Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal 2013-02-23 18:50:11 -08:00
entry_64.S KVM: VMX: Register a new IPI for posted interrupt 2013-04-16 16:32:39 -03:00
ftrace.c x86/ftrace: Use __pa_symbol instead of __pa on C visible symbols 2012-11-16 16:42:09 -08:00
head32.c x86: Merge early kernel reserve for 32bit and 64bit 2013-01-29 19:32:58 -08:00
head64.c x86: Fix bit corruption at CPU resume time 2013-05-20 11:36:03 -07:00
head_32.S Merge branch 'x86/microcode' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-22 19:22:52 -08:00
head_64.S x86-64, init: Fix a possible wraparound bug in switchover in head_64.S 2013-05-28 15:41:59 -07:00
head.c x86: Make sure we can boot in the case the BDA contains pure garbage 2013-02-27 13:38:57 -08:00
hpet.c x86, hpet: Introduce x86_msi_ops.setup_hpet_msi 2013-01-28 10:48:30 +01:00
hw_breakpoint.c
i386_ksyms_32.c x86-32: Add support for 64bit get_user() 2013-02-07 15:07:28 -08:00
i387.c x86: Allow FPU to be used at interrupt time even with eagerfpu 2013-05-30 16:36:42 -07:00
i8237.c
i8253.c
i8259.c x86/irq/i8259: Fix incorrect comment 2012-08-22 09:34:24 +02:00
io_delay.c
ioport.c x86: get rid of pt_regs argument of iopl(2) 2013-02-03 18:16:24 -05:00
irq_32.c
irq_64.c
irq_work.c x86, trace: Introduce entering/exiting_irq() 2013-06-20 22:25:01 -07:00
irq.c x86, trace: Introduce entering/exiting_irq() 2013-06-20 22:25:01 -07:00
irqinit.c KVM: VMX: Register a new IPI for posted interrupt 2013-04-16 16:32:39 -03:00
jump_label.c
kdebugfs.c arch/x86/kernel/kdebugfs.c: Ensure a consistent return value in error case 2012-07-26 15:07:20 +02:00
kgdb.c kgdb,x86: fix warning about unused variable 2012-10-12 06:37:34 -05:00
kvm.c context_tracking: Restore correct previous context state on exception exit 2013-03-07 17:10:11 +01:00
kvmclock.c Merge branch 'master' into queue 2013-03-04 20:10:32 -03:00
ldt.c
machine_kexec_32.c
machine_kexec_64.c x86, kexec, 64bit: Only set ident mapping for ram. 2013-01-29 15:26:35 -08:00
Makefile Merge branch 'x86/microcode' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-22 19:22:52 -08:00
microcode_amd.c x86, microcode, AMD: Add support for family 16h processors 2012-11-20 22:23:28 -08:00
microcode_core_early.c x86, microcode: Verify the family before dispatching microcode patching 2013-04-19 16:36:03 -07:00
microcode_core.c x86/microcode_intel.h: Define functions and macros for early loading ucode 2013-01-31 13:18:50 -08:00
microcode_intel_early.c x86/microcode: Add local mutex to fix physical CPU hot-add deadlock 2013-05-09 11:10:00 +02:00
microcode_intel_lib.c x86/microcode_intel_lib.c: Early update ucode on Intel's CPU 2013-01-31 13:19:14 -08:00
microcode_intel.c x86/microcode_intel.h: Define functions and macros for early loading ucode 2013-01-31 13:18:50 -08:00
mmconf-fam10h_64.c
module.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2012-07-24 13:34:56 -07:00
mpparse.c Merge branch 'x86-trampoline-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2012-05-29 20:14:53 -07:00
msr.c more file_inode() open-coded instances 2013-02-27 16:59:05 -05:00
nmi_selftest.c x86/nmi: Clean up register_nmi_handler() usage 2012-06-20 14:23:17 +02:00
nmi.c x86/nmi: export local_touch_nmi() symbol for modules 2013-01-17 22:25:57 +08:00
paravirt_patch_32.c
paravirt_patch_64.c
paravirt-spinlocks.c
paravirt.c Merge branch 'x86-paravirt-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-04-30 08:41:21 -07:00
pci-calgary_64.c x86/debug: Add KERN_<LEVEL> to bare printks, convert printks to pr_<level> 2012-06-06 09:17:22 +02:00
pci-dma.c x86/dma-debug: Bump PREALLOC_DMA_DEBUG_ENTRIES 2013-01-24 17:34:18 +01:00
pci-iommu_table.c
pci-nommu.c X86: integrate CMA with DMA-mapping subsystem 2012-05-21 15:09:38 +02:00
pci-swiotlb.c
pcspeaker.c
perf_regs.c perf: Fix off by one test in perf_reg_value() 2012-09-19 17:08:40 +02:00
probe_roms.c x86/pci/probe_roms: Add missing __iomem annotation to pci_map_biosrom() 2012-09-05 10:52:25 +02:00
process_32.c dump_stack: unify debug information printed by show_regs() 2013-04-30 17:04:02 -07:00
process_64.c dump_stack: unify debug information printed by show_regs() 2013-04-30 17:04:02 -07:00
process.c x86: Fix idle consolidation fallout 2013-05-07 16:24:03 +02:00
ptrace.c x86: ptrace.c only needs export.h and not the full module.h 2013-02-14 12:56:12 -08:00
pvclock.c x86/kvm: Fix pvclock vsyscall fixmap 2013-02-28 08:50:11 +02:00
quirks.c x86, quirks: Shut-up a long-standing gcc warning 2013-04-02 16:03:34 -07:00
reboot_fixups_32.c
reboot.c efi: Make 'efi_enabled' a function to query EFI facilities 2013-01-30 11:51:59 -08:00
relocate_kernel_32.S
relocate_kernel_64.S x86: Fix typo in kexec register clearing 2013-06-12 15:16:18 -07:00
resource.c
rtc.c x86: Do full rtc synchronization with ntp 2013-03-15 16:50:26 -07:00
setup_percpu.c x86: Add read_mostly declaration/definition to variables from smp.h 2012-06-14 12:42:11 +02:00
setup.c dump_stack: implement arch-specific hardware description in task dumps 2013-04-30 17:04:02 -07:00
signal.c x86: convert to ksignal 2013-02-14 09:21:17 -05:00
smp.c x86, trace: Introduce entering/exiting_irq() 2013-06-20 22:25:01 -07:00
smpboot.c x86: Use generic idle loop 2013-04-08 17:39:29 +02:00
stacktrace.c
step.c ptrace: ensure arch_ptrace/ptrace_request can never race with SIGKILL 2013-01-22 10:08:00 -08:00
sys_x86_64.c x86: Fix a typo 2013-01-24 16:22:10 +01:00
syscall_32.c
syscall_64.c
tboot.c Revert "x86-64/efi: Use EFI to deal with platform wall clock (again)" 2012-12-15 15:20:41 -08:00
tce_64.c
test_nx.c
test_rodata.c
time.c MCA: delete all remaining traces of microchannel bus support. 2012-05-17 19:06:13 -04:00
tls.c make SYSCALL_DEFINE<n>-generated wrappers do asmlinkage_protect 2013-03-03 22:58:33 -05:00
tls.h
topology.c x86, topology: Debug CPU0 hotplug 2012-11-14 15:28:11 -08:00
trace_clock.c tracing,x86: Add a TSC trace_clock 2012-11-13 15:48:27 -05:00
traps.c Merge branch 'x86-kaslr-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-04-30 08:37:24 -07:00
tsc_sync.c
tsc.c x86: tsc: Add support for new S3_NONSTOP feature 2013-03-15 16:51:18 -07:00
uprobes.c uretprobes/x86: Hijack return address 2013-04-13 15:31:55 +02:00
verify_cpu.S
vm86_32.c x86, vm86: fix VM86 syscalls: use SYSCALL_DEFINEx(...) 2013-05-02 20:36:32 -04:00
vmlinux.lds.S x86: Drop always empty .text..page_aligned section 2013-03-11 15:07:56 +01:00
vsmp_64.c x86/apic/x2apic: Limit the vector reservation to the user specified mask 2012-07-06 11:00:22 +02:00
vsyscall_64.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2012-12-16 15:40:50 -08:00
vsyscall_emu_64.S
vsyscall_trace.h
x86_init.c Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-02-21 18:06:55 -08:00
x8664_ksyms_64.c x86: Improve __phys_addr performance by making use of carry flags and inlining 2012-11-16 16:42:08 -08:00
xsave.c x86, smap: Do not abuse the [f][x]rstor_checking() functions for user space 2012-09-25 15:42:18 -07:00