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b8f8c3cf0a
linux_dsm_epyc7002/arch/powerpc/kernel
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Thomas Gleixner b8f8c3cf0a nohz: prevent tick stop outside of the idle loop 
Jack Ren and Eric Miao tracked down the following long standing
problem in the NOHZ code:

	scheduler switch to idle task
	enable interrupts

Window starts here

	----> interrupt happens (does not set NEED_RESCHED)
	      	irq_exit() stops the tick

	----> interrupt happens (does set NEED_RESCHED)

	return from schedule()
	
	cpu_idle(): preempt_disable();

Window ends here

The interrupts can happen at any point inside the race window. The
first interrupt stops the tick, the second one causes the scheduler to
rerun and switch away from idle again and we end up with the tick
disabled.

The fact that it needs two interrupts where the first one does not set
NEED_RESCHED and the second one does made the bug obscure and extremly
hard to reproduce and analyse. Kudos to Jack and Eric.

Solution: Limit the NOHZ functionality to the idle loop to make sure
that we can not run into such a situation ever again.

cpu_idle()
{
	preempt_disable();

	while(1) {
		 tick_nohz_stop_sched_tick(1); <- tell NOHZ code that we
		 			          are in the idle loop

		 while (!need_resched())
		       halt();

		 tick_nohz_restart_sched_tick(); <- disables NOHZ mode
		 preempt_enable_no_resched();
		 schedule();
		 preempt_disable();
	}
}

In hindsight we should have done this forever, but ... 

/me grabs a large brown paperbag.

Debugged-by: Jack Ren <jack.ren@marvell.com>, 
Debugged-by: eric miao <eric.y.miao@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2008-07-18 18:10:28 +02:00
..
vdso32 [POWERPC] vdso: Fixes for cache block sizes 2007-11-20 13:56:31 +11:00
vdso64 [POWERPC] vdso: Fixes for cache block sizes 2007-11-20 13:56:31 +11:00
align.c [POWERPC] Handle alignment faults on SPE load/store instructions 2007-09-14 08:51:48 -05:00
asm-offsets.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc 2008-04-29 08:19:14 -07:00
audit.c [PATCH] audit signal recipients 2007-05-11 05:38:25 -04:00
btext.c [POWERPC] Remove duplicate #include 2008-05-09 20:22:58 +10:00
clock.c [POWERPC] clk.h interface for platforms 2007-10-03 09:11:56 +10:00
compat_audit.c [PATCH] add SIGNAL syscall class (v3) 2007-05-11 05:38:25 -04:00
cpu_setup_6xx.S [POWERPC] ppc32: Fix errata for 603 CPUs 2008-04-21 15:00:32 -05:00
cpu_setup_44x.S [POWERPC] 4xx: Fix 460GT support to not enable FPU 2008-04-24 13:32:47 -05:00
cpu_setup_pa6t.S [POWERPC] pasemi: Enable one more hid bit 2007-04-24 21:31:49 +10:00
cpu_setup_ppc970.S [POWERPC] powerpc: Enable DEEPNAP power savings mode on 970MP 2006-10-16 16:32:25 +10:00
cputable.c [POWERPC] Fix default cputable entries for e200 and e500 families 2008-05-12 14:20:35 +10:00
crash_dump.c [LIB]: Make PowerPC LMB code generic so sparc64 can use it too. 2008-02-13 16:56:49 -08:00
crash.c [LIB]: Make PowerPC LMB code generic so sparc64 can use it too. 2008-02-13 16:56:49 -08:00
dma_64.c iommu sg: powerpc: convert iommu to use the IOMMU helper 2008-02-05 09:44:11 -08:00
entry_32.S [POWERPC] Add IRQSTACKS support on ppc32 2008-04-29 15:57:34 +10:00
entry_64.S [POWERPC] irqtrace support for 64-bit powerpc 2008-04-18 15:38:47 +10:00
firmware.c
fpu.S [POWERPC] Restore copyright notice in arch/powerpc/kernel/fpu.S 2006-08-30 14:45:35 +10:00
head_8xx.S [POWERPC] 8xx: fix swap 2008-03-07 08:42:28 -06:00
head_32.S [POWERPC] Move stackframe definitions to common header 2008-04-18 15:37:18 +10:00
head_40x.S [POWERPC] Fix swapper_pg_dir size when CONFIG_PTE_64BIT=y on FSL_BOOKE 2007-12-06 13:11:04 -06:00
head_44x.S [POWERPC] 4xx: Fix problem with new TLB storage attibute fields on 440x6 core 2008-05-06 10:36:20 -05:00
head_64.S [POWERPC] Fix bogus paca->_current initialization 2008-05-09 20:22:58 +10:00
head_booke.h [POWERPC] Rework Book-E debug exception handling 2008-04-17 01:01:36 -05:00
head_fsl_booke.S [POWERPC] 85xx: Add support for relocatable kernel (and booting at non-zero) 2008-04-24 20:58:01 +10:00
ibmebus.c [POWERPC] Replace remaining __FUNCTION__ occurrences 2008-04-01 20:43:09 +11:00
idle_6xx.S
idle_power4.S [POWERPC] powermac: Support G5 CPU hotplug 2007-05-07 20:31:13 +10:00
idle.c nohz: prevent tick stop outside of the idle loop 2008-07-18 18:10:28 +02:00
init_task.c [PATCH] take init_files to fs/file.c 2008-05-16 17:22:20 -04:00
io.c [POWERPC] Move inline asm eieio to using eieio inline function 2007-07-10 00:33:14 -05:00
iomap.c [POWERPC] Add 64-bit resources support to pci_iomap 2007-09-20 07:36:52 -05:00
iommu.c [POWERPC] Replace remaining __FUNCTION__ occurrences 2008-04-01 20:43:09 +11:00
irq.c [POWERPC] Add IRQSTACKS support on ppc32 2008-04-29 15:57:34 +10:00
isa-bridge.c [POWERPC] Remove leftover printk in isa-bridge.c 2008-05-09 20:22:59 +10:00
kprobes.c [POWERPC] Kill sparse warnings in kprobes 2008-02-20 13:33:37 +11:00
l2cr_6xx.S Convert files to UTF-8 and some cleanups 2007-10-19 23:21:04 +02:00
legacy_serial.c [POWERPC] Fix legacy serial search for opb bus ports 2008-02-06 16:30:00 +11:00
lparcfg.c powerpc: use non-racy method for proc entries creation 2008-04-29 08:06:22 -07:00
machine_kexec_32.c
machine_kexec_64.c [POWERPC] Rename get_property to of_get_property: arch/powerpc 2007-04-13 03:55:19 +10:00
machine_kexec.c [POWERPC] Fix crashkernel= handling when no crashkernel= specified 2008-04-30 19:49:48 +10:00
Makefile [POWERPC] ppc: Don't run prom_init_check for arch/ppc builds 2008-05-12 20:27:50 +10:00
misc_32.S [POWERPC] Add IRQSTACKS support on ppc32 2008-04-29 15:57:34 +10:00
misc_64.S [POWERPC] Clean up misc_64.S 2008-04-24 20:58:03 +10:00
misc.S [POWERPC] Make setjmp/longjmp code usable outside of xmon 2008-01-25 22:52:50 +11:00
module_32.c [POWERPC] Optimize counting distinct entries in the relocation sections 2007-12-21 15:05:58 +11:00
module_64.c [POWERPC] Optimize counting distinct entries in the relocation sections 2007-12-21 15:05:58 +11:00
msi.c [POWERPC] PowerPC MSI infrastructure 2007-05-08 13:40:31 +10:00
nvram_64.c [POWERPC] pseries: Eliminate global error_log_cnt variable 2007-08-17 11:01:52 +10:00
of_device.c [POWERPC] Use <linux/of_{platform, device}.h> and not <asm/...> variants. 2008-01-17 14:58:57 +11:00
of_platform.c [POWERPC] cell: Generalize io-workarounds code 2008-04-24 21:08:12 +10:00
paca.c [POWERPC] Raise the upper limit of NR_CPUS and move the pacas into the BSS 2008-04-24 20:58:04 +10:00
pci_32.c [POWERPC] Remove update_bridge_resource 2008-01-23 19:32:30 -06:00
pci_64.c [POWERPC] Always hookup PHB IO resource even when empty 2008-01-25 22:52:53 +11:00
pci_dn.c [POWERPC] iSeries: eliminate pci_dn bussubno 2008-01-17 14:57:05 +11:00
pci-common.c PCI: powerpc: use generic pci_enable_resources() 2008-04-20 21:47:05 -07:00
pmc.c [POWERPC] Made FSL Book-E PMC support more generic 2008-02-05 23:34:14 -06:00
ppc32.h Revert "[POWERPC] Add compat handler for PTRACE_GETSIGINFO" 2008-04-24 14:05:15 +10:00
ppc_ksyms.c Basic braille screen reader support 2008-04-30 08:29:52 -07:00
proc_ppc64.c powerpc: use non-racy method for proc entries creation 2008-04-29 08:06:22 -07:00
process.c [POWERPC] Add IRQSTACKS support on ppc32 2008-04-29 15:57:34 +10:00
prom_init_check.sh [POWERPC] Add kernstart_addr to list of allowed symbols in prom_init 2008-05-23 16:15:35 +10:00
prom_init.c [POWERPC] Efika: Really, don't pretend to be CHRP 2008-04-17 07:46:12 +10:00
prom_parse.c [POWERPC] Add of_translate_dma_address 2007-12-11 15:43:35 +11:00
prom.c [POWERPC] 85xx: Add support for relocatable kernel (and booting at non-zero) 2008-04-24 20:58:01 +10:00
ptrace32.c Revert "[POWERPC] Add compat handler for PTRACE_GETSIGINFO" 2008-04-24 14:05:15 +10:00
ptrace.c [POWERPC] user_regset PTRACE_SETREGS regression fix 2008-03-20 10:10:56 +11:00
rtas_flash.c powerpc: use non-racy method for proc entries creation 2008-04-29 08:06:22 -07:00
rtas_pci.c [POWERPC] Convert pci and eeh code to of_device_is_available 2008-04-07 13:49:25 +10:00
rtas-proc.c powerpc: use non-racy method for proc entries creation 2008-04-29 08:06:22 -07:00
rtas-rtc.c
rtas.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc 2008-04-21 15:50:49 -07:00
setup_32.c [POWERPC] Add IRQSTACKS support on ppc32 2008-04-29 15:57:34 +10:00
setup_64.c [POWERPC] Initialize lockdep earlier 2008-05-09 20:22:58 +10:00
setup-common.c [POWERPC] Add 'model: ...' line to common show_cpuinfo() 2008-03-26 08:44:04 +11:00
setup.h
signal_32.c [POWERPC] Define copy_siginfo_from_user32 2008-04-20 13:03:36 +10:00
signal_64.c [POWERPC] Implement logging of unhandled signals 2007-10-12 14:05:18 +10:00
signal.c [POWERPC] Implement logging of unhandled signals 2007-10-12 14:05:18 +10:00
signal.h [POWERPC] Less ifdef's in signal.c/signal.h 2007-06-14 22:29:58 +10:00
smp-tbsync.c [POWERPC] Replace kmalloc+memset with kzalloc 2006-12-04 20:42:09 +11:00
smp.c [POWERPC] Bolt in SLB entry for kernel stack on secondary cpus 2008-05-02 15:00:45 +10:00
softemu8xx.c [POWERPC] 8xx: Move softemu8xx.c from arch/ppc 2007-10-04 11:02:54 -05:00
stacktrace.c [POWERPC] Fix new warnings arising from stacktrace patch 2008-04-24 20:58:02 +10:00
suspend.c [PATCH] x86: Move swsusp __pa() dependent code to arch portion 2007-05-02 19:27:07 +02:00
swsusp_32.S [POWERPC] Make altivec code in swsusp_32.S depend on CONFIG_ALTIVEC 2007-11-08 14:15:34 +11:00
swsusp_64.c [POWERPC] powermac: Suspend to disk on G5 2007-05-07 20:31:14 +10:00
swsusp_asm64.S [POWERPC] powermac: Suspend to disk on G5 2007-05-07 20:31:14 +10:00
swsusp.c powerpc: fixup hard_irq_disable semantics 2007-05-11 08:29:34 -07:00
sys_ppc32.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc 2008-04-21 15:50:49 -07:00
syscalls.c unified (weak) sys_pipe implementation 2008-05-03 13:50:33 -07:00
sysfs.c remove __attribute_used__ 2008-01-28 23:21:18 +01:00
systbl_chk.c [POWERPC] Fix a couple of copyright symbols 2008-01-25 22:52:50 +11:00
systbl_chk.sh [POWERPC] Fix a couple of copyright symbols 2008-01-25 22:52:50 +11:00
systbl.S [POWERPC] Align the sys_call_table 2007-10-11 14:36:47 +10:00
tau_6xx.c
time.c ntp: rename TICK_LENGTH_SHIFT to NTP_SCALE_SHIFT 2008-05-01 08:03:59 -07:00
traps.c [POWERPC] Fix compilation for CONFIG_DEBUGGER=n and CONFIG_KEXEC=y 2008-02-07 11:40:18 +11:00
udbg_16550.c [POWERPC] 4xx: Add early udbg support for 40x processors 2007-12-23 13:13:03 -06:00
udbg.c [POWERPC] Mark udbg console as CON_ANYTIME, ie. callable early in boot 2008-04-24 21:08:11 +10:00
vdso.c Merge master.kernel.org:/pub/scm/linux/kernel/git/davem/lmb-2.6 2008-02-26 21:08:45 +11:00
vecemu.c
vector.S
vio.c [POWERPC] Replace remaining __FUNCTION__ occurrences 2008-04-01 20:43:09 +11:00
vmlinux.lds.S [POWERPC] Update linker script to properly set physical addresses 2008-04-17 07:46:14 +10:00