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b96f7d881a
linux_dsm_epyc7002/arch/s390/include/asm
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Martin Schwidefsky b96f7d881a s390/spinlock: introduce spinlock wait queueing 
The queued spinlock code for s390 follows the principles of the common
code qspinlock implementation but with a few notable differences.

The format of the spinlock_t locking word differs, s390 needs to store
the logical CPU number of the lock holder in the spinlock_t to be able
to use the diagnose 9c directed yield hypervisor call.

The inline code sequences for spin_lock and spin_unlock are nice and
short. The inline portion of a spin_lock now typically looks like this:

	lhi	%r0,0			# 0 indicates an empty lock
	l	%r1,0x3a0		# CPU number + 1 from lowcore
	cs	%r0,%r1,<some_lock>	# lock operation
	jnz	call_wait		# on failure call wait function
locked:
	...
call_wait:
	la	%r2,<some_lock>
	brasl	%r14,arch_spin_lock_wait
	j	locked

A spin_unlock is as simple as before:

	lhi	%r0,0
	sth	%r0,2(%r2)		# unlock operation

After a CPU has queued itself it may not enable interrupts again for the
arch_spin_lock_flags() variant. The arch_spin_lock_wait_flags wait function
is removed.

To improve performance the code implements opportunistic lock stealing.
If the wait function finds a spinlock_t that indicates that the lock is
free but there are queued waiters, the CPU may steal the lock up to three
times without queueing itself. The lock stealing update the steal counter
in the lock word to prevent more than 3 steals. The counter is reset at
the time the CPU next in the queue successfully takes the lock.

While the queued spinlocks improve performance in a system with dedicated
CPUs, in a virtualized environment with continuously overcommitted CPUs
the queued spinlocks can have a negative effect on performance. This
is due to the fact that a queued CPU that is preempted by the hypervisor
will block the queue at some point even without holding the lock. With
the classic spinlock it does not matter if a CPU is preempted that waits
for the lock. Therefore use the queued spinlock code only if the system
runs with dedicated CPUs and fall back to classic spinlocks when running
with shared CPUs.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2017-09-28 07:29:44 +02:00
..
fpu s390/fpu: improve kernel_fpu_[begin|end] 2016-08-29 11:05:01 +02:00
trace s390/zcrypt: tracepoint definitions for zcrypt device driver. 2016-12-14 16:33:40 +01:00
airq.h
ap.h s390/zcrypt: externalize AP queue interrupt control 2017-09-06 09:24:42 +02:00
appldata.h
archrandom.h s390/crypto: Provide s390 specific arch random functionality. 2017-04-26 13:41:35 +02:00
asm-prototypes.h s390/kbuild: enable modversions for symbols exported from asm 2016-12-20 15:22:56 +01:00
atomic_ops.h s390/spinlock: use atomic primitives for spinlocks 2017-04-12 08:43:33 +02:00
atomic.h s390/atomic: refactor atomic primitives 2016-11-11 16:37:33 +01:00
barrier.h s390: more efficient smp barriers 2016-01-12 20:47:05 +02:00
bitops.h s390/bitops: remove outdated comment 2017-03-22 08:29:05 +01:00
bug.h debug: Fix WARN_ON_ONCE() for modules 2017-07-20 12:31:04 +02:00
bugs.h
cache.h s390: use __section macro everywhere 2016-06-13 15:58:23 +02:00
ccwdev.h
ccwgroup.h
checksum.h Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
chpid.h
cio.h vfio: ccw: introduce support for ccw0 2017-03-31 12:55:12 +02:00
clp.h s390/pci: add ioctl interface for CLP 2016-03-07 16:54:32 +01:00
cmb.h
cmpxchg.h s390/cmpxchg: remove dead code 2015-10-14 14:32:15 +02:00
compat.h teach SYSCALL_DEFINE/COMPAT_SYSCALL_DEFINE to handle __bitwise arguments 2017-08-31 17:32:37 -04:00
cpacf.h Merge branch 's390forkvm' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into features 2017-04-27 07:34:07 +02:00
cpcmd.h s390/cpcmd,vmcp: avoid GFP_DMA allocations 2017-08-09 09:09:35 -04:00
cpu_mf.h s390/cpu_mf: remove register variable in __ecctr() 2017-03-31 07:53:34 +02:00
cpu.h
cpufeature.h
cputime.h s390/cputime: provide archicture specific cputime_to_nsecs 2017-03-01 09:59:27 +01:00
crw.h s390/cio: Consolidate inline assemblies and related data definitions 2015-12-18 14:59:34 +01:00
css_chars.h
ctl_reg.h KVM: s390: implement instruction execution protection for emulated 2017-06-22 12:41:06 +02:00
current.h
debug.h s390: convert debug_info.ref_count from atomic_t to refcount_t 2017-05-11 16:35:32 +02:00
delay.h
diag.h s390/diag: add diag26c support 2017-06-20 15:44:15 -04:00
dis.h s390/uprobes: fix compile for !KPROBES 2017-05-03 09:08:57 +02:00
dma-mapping.h s390: implement ->mapping_error 2017-06-28 06:54:31 -07:00
dma.h
eadm.h block: introduce new block status code type 2017-06-09 09:27:32 -06:00
ebcdic.h s390: remove asm/mman.h and asm/types.h 2017-08-02 11:15:36 +02:00
elf.h s390/mm: use new mm defines instead of magic values 2017-07-26 08:25:09 +02:00
exec.h
extable.h s390: switch to extable.h 2017-03-28 18:23:55 -04:00
extmem.h
facility.h s390/facilities: get rid of __ASSEMBLY__ in facility header file 2017-03-22 08:29:18 +01:00
fcx.h s390: use canonical include guard style 2016-06-13 15:58:17 +02:00
ftrace.h s390/dumpstack: get rid of return_address again 2016-10-17 14:44:33 +02:00
futex.h futex: Remove duplicated code and fix undefined behaviour 2017-08-25 22:49:59 +02:00
gmap.h KVM: s390: backup the currently enabled gmap when scheduled out 2016-06-20 09:55:24 +02:00
hardirq.h
hugetlb.h mm/hugetlb: allow architectures to override huge_pte_clear() 2017-07-06 16:24:34 -07:00
hw_irq.h
idals.h Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
idle.h
io.h s390: provide default ioremap and iounmap declaration 2017-06-12 16:26:00 +02:00
ipl.h s390/mm: use new mm defines instead of magic values 2017-07-26 08:25:09 +02:00
irq.h s390: use SPARSE_IRQ 2016-06-13 15:58:24 +02:00
irqflags.h s390/irqflags: optimize irq restore 2016-01-19 12:14:01 +01:00
isc.h vfio: ccw: basic implementation for vfio_ccw driver 2017-03-31 12:55:04 +02:00
itcw.h
jump_label.h s390: add explicit <linux/stringify.h> for jump label 2016-06-13 15:58:16 +02:00
Kbuild s390: use generic asm/unaligned.h 2017-08-03 13:16:28 +02:00
kdebug.h
kexec.h s390/crash: Remove unused KEXEC_NOTE_BYTES 2017-07-05 07:35:29 +02:00
kprobes.h s390/uprobes: fix compile for !KPROBES 2017-05-03 09:08:57 +02:00
kvm_host.h KVM: s390: Multiple Epoch Facility support 2017-08-29 15:15:54 +02:00
kvm_para.h
linkage.h
livepatch.h s390: Audit and remove any remaining unnecessary uses of module.h 2017-02-17 07:40:41 +01:00
lowcore.h s390/spinlock: introduce spinlock wait queueing 2017-09-28 07:29:44 +02:00
mmu_context.h s390/mm: use a single lock for the fields in mm_context_t 2017-09-06 09:24:43 +02:00
mmu.h s390/mm: use a single lock for the fields in mm_context_t 2017-09-06 09:24:43 +02:00
mmzone.h
module.h
nmi.h s390/nmi: keep comments consistent 2017-08-02 11:15:34 +02:00
numa.h
os_info.h s390/dump: streamline oldmem copy functions 2015-11-27 09:24:12 +01:00
page-states.h KVM: s390: expose no-DAT to guest and migration support 2017-08-29 15:15:56 +02:00
page.h s390/mm: add missing virt_to_pfn() etc. helper functions 2017-08-09 09:09:22 -04:00
pci_clp.h s390/pci: use proper endianness annotations 2017-01-16 07:27:53 +01:00
pci_debug.h
pci_dma.h s390/pci_dma: fix DMA table corruption with > 4 TB main memory 2015-11-27 09:24:15 +01:00
pci_insn.h s390/pci: improve error handling during interrupt deregistration 2017-06-28 07:32:08 +02:00
pci_io.h s390/pci: improve ZPCI_* macros 2016-01-26 12:45:49 +01:00
pci.h iommu/s390: Add support for iommu_device handling 2017-08-15 18:22:45 +02:00
percpu.h s390/percpu: remove this_cpu_cmpxchg_double_4 2016-03-02 06:44:30 -06:00
perf_event.h s390/cpum_cf: update counter numbers to ecctr limits 2017-03-31 07:53:26 +02:00
pgalloc.h s390/mm,vmem: simplify region and segment table allocation code 2017-07-26 08:25:12 +02:00
pgtable.h s390/mm: make pmdp_invalidate() do invalidation only 2017-09-19 08:36:19 +02:00
pkey.h s390/pkey: Introduce new API for secure key verification 2017-03-22 08:29:13 +01:00
preempt.h s390/preempt: move preempt_count to the lowcore 2016-11-11 16:37:40 +01:00
processor.h s390/topology: add detection of dedicated vs shared CPUs 2017-09-28 07:29:43 +02:00
ptrace.h s390/kvm: avoid global config of vm.alloc_pgste=1 2017-06-13 13:03:41 +02:00
qdio.h s390/mm: use new mm defines instead of magic values 2017-07-26 08:25:09 +02:00
reset.h s390/dump: rework CPU register dump code 2015-11-27 09:24:14 +01:00
runtime_instr.h s390/runtime_instrumentation: clean up struct runtime_instr_cb 2017-09-28 07:29:40 +02:00
rwsem.h locking/rwsem: Remove rwsem_atomic_add() and rwsem_atomic_update() 2016-06-08 15:16:59 +02:00
schid.h
sclp.h s390/sclp: Detect KSS facility 2017-04-21 11:08:04 +02:00
scsw.h s390/dasd: channel path aware error recovery 2016-12-12 12:05:03 +01:00
seccomp.h s390/seccomp: include generic seccomp header file 2016-04-01 17:20:55 +02:00
sections.h mm: fix section name for .data..ro_after_init 2017-03-31 17:13:30 -07:00
segment.h
serial.h
set_memory.h treewide: move set_memory_* functions away from cacheflush.h 2017-05-08 17:15:13 -07:00
setup.h s390/vmcp: make use of contiguous memory allocator 2017-08-09 09:09:35 -04:00
shmparam.h
signal.h
sigp.h s390/smp: use sigp condition code define 2017-06-12 16:25:58 +02:00
smp.h s390/smp: initialize cpu_present_mask in setup_arch 2016-12-07 07:23:07 +01:00
sparsemem.h s390: make MAX_PHYSMEM_BITS configurable 2017-03-28 16:55:10 +02:00
spinlock_types.h s390/spinlock: use atomic primitives for spinlocks 2017-04-12 08:43:33 +02:00
spinlock.h s390/spinlock: introduce spinlock wait queueing 2017-09-28 07:29:44 +02:00
stp.h s390/time: remove ETR support 2016-06-13 15:58:21 +02:00
string.h s390: add support for FORTIFY_SOURCE 2017-09-28 07:29:40 +02:00
switch_to.h s390: add a system call for guarded storage 2017-03-22 08:14:25 +01:00
syscall.h s390/syscalls: Fix out of bounds arguments access 2017-07-05 07:35:30 +02:00
sysinfo.h s390/topology: add detection of dedicated vs shared CPUs 2017-09-28 07:29:43 +02:00
termios.h
thread_info.h s390/kvm: avoid global config of vm.alloc_pgste=1 2017-06-13 13:03:41 +02:00
timex.h s390/dasd: Change unsigned long long to unsigned long 2017-08-23 13:31:51 +02:00
tlb.h Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2017-09-05 09:45:46 -07:00
tlbflush.h s390/mm: fix race on mm->context.flush_mm 2017-09-06 09:24:42 +02:00
topology.h s390/topology: add detection of dedicated vs shared CPUs 2017-09-28 07:29:43 +02:00
uaccess.h Merge branch 'work.uaccess-unaligned' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-07-15 11:17:52 -07:00
unistd.h s390: ignore pkey system calls 2016-10-17 11:25:25 +02:00
uprobes.h uprobes: remove function declarations from arch/{mips,s390} 2016-10-07 18:46:30 -07:00
user.h
vdso.h s390/time: steer clocksource on STP sync events 2016-10-28 10:09:02 +02:00
vga.h
vtime.h
vtimer.h
vx-insn.h RAID/s390: add SIMD implementation for raid6 gen/xor 2016-08-29 11:05:04 +02:00
xor.h s390/xor: optimized xor routing using the XC instruction 2016-02-23 08:56:17 +01:00