AuxXxilium/linux_dsm_epyc7002
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b8f8c3cf0a
linux_dsm_epyc7002/arch/sparc64/kernel
History
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
..
asm-offsets.c kbuild: frv,m32r,sparc64 introduce fake asm-offsets.h file 2005-09-09 22:47:53 +02:00
audit.c sparc64: Kill CONFIG_SPARC32_COMPAT 2008-04-26 21:41:19 -07:00
auxio.c [SPARC/64]: Move of_platform_driver initialisations: arch/sparc{,64}. 2007-10-13 21:53:12 -07:00
central.c [SPARC64]: __inline__ --> inline 2007-10-27 00:13:04 -07:00
cherrs.S sparc64: Split entry.S up into seperate files. 2008-04-28 00:47:20 -07:00
chmc.c [SPARC64]: Fix memory controller register access when non-SMP. 2007-12-07 01:10:14 -08:00
compat_audit.c [PATCH] add SIGNAL syscall class (v3) 2007-05-11 05:38:25 -04:00
cpu.c [SPARC64]: Fix sparse warnings in arch/sparc64/kernel/{cpu,setup}.c 2008-03-25 21:51:40 -07:00
ds.c [SPARC64]: Use shorter list_splice_init() for brevity. 2008-03-23 22:48:29 -07:00
dtlb_miss.S [SPARC64]: More TLB/TSB handling fixes. 2006-03-20 01:13:34 -08:00
dtlb_prot.S sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
ebus.c sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
entry.h [SPARC64]: %l6 trap return handling no longer necessary. 2008-04-24 03:15:22 -07:00
etrap.S sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
fpu_traps.S sparc64: Split entry.S up into seperate files. 2008-04-28 00:47:20 -07:00
getsetcc.S sparc64: Split entry.S up into seperate files. 2008-04-28 00:47:20 -07:00
head.S sparc64: Split entry.S up into seperate files. 2008-04-28 00:47:20 -07:00
helpers.S sparc64: Split entry.S up into seperate files. 2008-04-28 00:47:20 -07:00
hvapi.c [SPARC64]: Report proper system soft state to the hypervisor. 2007-05-29 02:49:29 -07:00
hvcalls.S sparc64: Split entry.S up into seperate files. 2008-04-28 00:47:20 -07:00
hvtramp.S [SPARC64]: Fix cpu trampoline et al. mismatch warnings. 2008-02-20 22:22:16 -08:00
idprom.c sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
init_task.c [PATCH] take init_files to fs/file.c 2008-05-16 17:22:20 -04:00
iommu_common.h sparc64: remove unused calc_npages() in iommu_common.h 2008-03-28 15:56:01 -07:00
iommu.c [SPARC64]: NUMA device infrastructure. 2008-04-23 23:32:16 -07:00
irq.c sparc64: Fix wedged irq regression. 2008-04-26 21:41:15 -07:00
itlb_miss.S [SPARC64]: Fix _PAGE_EXEC_4U check in sun4u I-TLB miss handler. 2007-05-29 02:50:15 -07:00
ivec.S sparc64: Split entry.S up into seperate files. 2008-04-28 00:47:20 -07:00
kgdb.c sparc: Add kgdb support. 2008-04-29 02:38:50 -07:00
kprobes.c [SPARC64]: Fix sparse warnings wrt. __show_regs(). 2008-02-19 20:48:58 -08:00
ktlb.S [SPARC64]: Fix build with SPARSEMEM_VMEMMAP disabled. 2008-01-12 21:52:16 -08:00
ldc.c [SPARC64]: Missing mdesc_release() in ldc_init(). 2007-12-05 05:37:55 -08:00
Makefile sparc: Add kgdb support. 2008-04-29 02:38:50 -07:00
mdesc.c [SPARC64]: Initialize MDESC earlier and use lmb_alloc() 2008-04-23 23:32:12 -07:00
misctrap.S sparc: Add kgdb support. 2008-04-29 02:38:50 -07:00
module.c [SPARC]: Remove duplicate includes. 2007-11-06 21:23:11 -08:00
of_device.c sparc64: Do not ignore 'pmu' device ranges. 2008-04-26 21:41:20 -07:00
pci_common.c sparc64: Stop creating dummy root PCI host controller devices. 2008-05-02 05:22:50 -07:00
pci_fire.c [SPARC64]: NUMA device infrastructure. 2008-04-23 23:32:16 -07:00
pci_impl.h sparc64: Stop creating dummy root PCI host controller devices. 2008-05-02 05:22:50 -07:00
pci_msi.c [SPARC64]: NUMA device infrastructure. 2008-04-23 23:32:16 -07:00
pci_psycho.c [SPARC64]: NUMA device infrastructure. 2008-04-23 23:32:16 -07:00
pci_sabre.c [SPARC64]: NUMA device infrastructure. 2008-04-23 23:32:16 -07:00
pci_schizo.c [SPARC64]: NUMA device infrastructure. 2008-04-23 23:32:16 -07:00
pci_sun4v_asm.S [SPARC64]: Add PCI MSI support on Niagara. 2007-02-10 23:50:37 -08:00
pci_sun4v.c [SPARC64]: NUMA device infrastructure. 2008-04-23 23:32:16 -07:00
pci_sun4v.h [SPARC64]: Add PCI MSI support on Niagara. 2007-02-10 23:50:37 -08:00
pci.c sparc64: Stop creating dummy root PCI host controller devices. 2008-05-02 05:22:50 -07:00
power.c [SPARC64]: Fix sparse warnings wrt. machine_alt_power_off(). 2008-02-19 20:39:18 -08:00
process.c nohz: prevent tick stop outside of the idle loop 2008-07-18 18:10:28 +02:00
prom.c [SPARC64]: Use lmb_alloc() for PROM device tree. 2008-04-23 23:32:11 -07:00
ptrace.c sparc: Fix debugger syscall restart interactions. 2008-05-11 02:07:19 -07:00
rtrap.S sparc64: Prevent stack backtrace false positives on trap frames. 2008-05-21 21:50:01 -07:00
sbus.c sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
setup.c sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
signal32.c sparc64: Use a TS_RESTORE_SIGMASK 2008-05-12 22:45:15 -07:00
signal.c sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
smp.c sparc64: Add global register dumping facility. 2008-05-20 00:33:45 -07:00
sparc64_ksyms.c sparc64: Kill unused local ISA bus layer. 2008-04-26 21:41:23 -07:00
spiterrs.S sparc64: Split entry.S up into seperate files. 2008-04-28 00:47:20 -07:00
sstate.c [SPARC64]: Report proper system soft state to the hypervisor. 2007-05-29 02:49:29 -07:00
stacktrace.c sparc64: Fix stack tracing through trap frames. 2008-05-21 18:15:53 -07:00
starfire.c sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
sun4v_ivec.S [SPARC64]: Use sun4v VIRQ interfaces as intended. 2007-10-13 21:53:16 -07:00
sun4v_tlb_miss.S [SPARC64]: %l6 trap return handling no longer necessary. 2008-04-24 03:15:22 -07:00
sys32.S sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
sys_sparc32.c sparc: Fix mremap address range validation. 2008-05-12 16:33:33 -07:00
sys_sparc.c sparc: Fix mremap address range validation. 2008-05-12 16:33:33 -07:00
syscalls.S sparc64: Split entry.S up into seperate files. 2008-04-28 00:47:20 -07:00
sysfs.c [SPARC64]: Add NUMA support. 2008-04-23 23:32:17 -07:00
systbls.h [SPARC]: Remove SunOS and Solaris binary support. 2008-04-21 15:10:15 -07:00
systbls.S sparc64: use compat_sys_utimes instead of home-grown local copy. 2008-05-05 12:32:39 -07:00
time.c [SPARC64]: Fix sparse warnings in arch/sparc64/kernel/time.c 2008-03-26 01:11:55 -07:00
trampoline.S sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
traps.c sparc64: Fix stack tracing through trap frames. 2008-05-21 18:15:53 -07:00
tsb.S [SPARC64]: %l6 trap return handling no longer necessary. 2008-04-24 03:15:22 -07:00
ttable.S sparc: Add kgdb support. 2008-04-29 02:38:50 -07:00
una_asm.S [SPARC64]: Mark __ex_table section correctly. 2006-03-04 23:23:56 -08:00
unaligned.c sparc64: remove CVS keywords 2008-05-20 00:33:43 -07:00
us2e_cpufreq.c [CPUFREQ] move policy's governor initialisation out of low-level drivers into cpufreq core 2007-10-04 18:40:57 -04:00
us3_cpufreq.c [SPARC64]: kzalloc() conversion 2006-03-20 01:14:19 -08:00
utrap.S sparc64: Split entry.S up into seperate files. 2008-04-28 00:47:20 -07:00
vio.c [SPARC64]: Fix of section mismatch warnings. 2008-01-21 22:34:30 -08:00
viohs.c viohs: extern on function definition 2007-07-26 11:11:56 -07:00
visemul.c [SPARC64]: Call do_mathemu on illegal instruction traps too. 2006-12-10 02:39:32 -08:00
vmlinux.lds.S all archs: consolidate init and exit sections in vmlinux.lds.h 2008-01-28 23:21:17 +01:00
winfixup.S [SPARC64]: %l6 trap return handling no longer necessary. 2008-04-24 03:15:22 -07:00