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Peter Zijlstra 2c61002271 locking/qspinlock: Fix spin_unlock_wait() some more 
While this prior commit:

  54cf809b95 ("locking,qspinlock: Fix spin_is_locked() and spin_unlock_wait()")

... fixes spin_is_locked() and spin_unlock_wait() for the usage
in ipc/sem and netfilter, it does not in fact work right for the
usage in task_work and futex.

So while the 2 locks crossed problem:

	spin_lock(A)		spin_lock(B)
	if (!spin_is_locked(B)) spin_unlock_wait(A)
	  foo()			foo();

... works with the smp_mb() injected by both spin_is_locked() and
spin_unlock_wait(), this is not sufficient for:

	flag = 1;
	smp_mb();		spin_lock()
	spin_unlock_wait()	if (!flag)
				  // add to lockless list
	// iterate lockless list

... because in this scenario, the store from spin_lock() can be delayed
past the load of flag, uncrossing the variables and loosing the
guarantee.

This patch reworks spin_is_locked() and spin_unlock_wait() to work in
both cases by exploiting the observation that while the lock byte
store can be delayed, the contender must have registered itself
visibly in other state contained in the word.

It also allows for architectures to override both functions, as PPC
and ARM64 have an additional issue for which we currently have no
generic solution.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Giovanni Gherdovich <ggherdovich@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Pan Xinhui <xinhui.pan@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <waiman.long@hpe.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: stable@vger.kernel.org # v4.2 and later
Fixes: 54cf809b95 ("locking,qspinlock: Fix spin_is_locked() and spin_unlock_wait()")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 		2016-06-08 14:29:08 +02:00
..
bitops bitops: Do not default to __clear_bit() for __clear_bit_unlock() 2016-03-21 10:50:48 +01:00
4level-fixup.h mm, asm-generic: define PUD_SHIFT in <asm-generic/4level-fixup.h> 2015-02-11 17:06:03 -08:00
Kbuild.asm UAPI: Set up uapi/asm/Kbuild.asm 2012-10-02 18:01:56 +01:00
asm-offsets.h asm-generic: Add common asm-offsets.h 2015-06-23 13:35:49 +09:00
atomic-long.h include/asm-generic/atomic-long.h: force inlining of some atomic_long operations 2016-03-17 15:09:34 -07:00
atomic.h atomic, arch: Audit atomic_{read,set}() 2015-09-23 09:54:28 +02:00
atomic64.h atomic: Provide atomic_{or,xor,and} 2015-07-27 14:06:24 +02:00
audit_change_attr.h audit: Modify a set of system calls in audit class definitions 2014-01-17 17:01:46 -05:00
audit_dir_write.h audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
audit_read.h audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
audit_signal.h
…
audit_write.h audit: Modify a set of system calls in audit class definitions 2014-01-17 17:01:46 -05:00
barrier.h asm-generic: implement virt_xxx memory barriers 2016-01-12 20:46:59 +02:00
bitops.h arch: Prepare for smp_mb__{before,after}_atomic() 2014-04-18 11:40:30 +02:00
bitsperlong.h UAPI: (Scripted) Disintegrate include/asm-generic 2012-10-04 18:20:15 +01:00
bug.h asm-generic changes for 4.6 2016-03-24 23:13:48 -07:00
bugs.h
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cache.h
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cacheflush.h asm-generic/cacheflush.h: flush icache when copying to user pages 2011-05-25 08:39:37 -07:00
checksum.h ipv4: Update parameters for csum_tcpudp_magic to their original types 2016-03-13 23:55:13 -04:00
clkdev.h asm-generic: COMMON_CLK defines __clk_{get,put} 2014-09-25 18:00:45 -07:00
cmpxchg-local.h LLVMLinux: Remove warning about returning an uninitialized variable 2014-04-09 13:44:35 -07:00
cmpxchg.h asm-generic: cmpxchg: avoid warnings from macro-ized cmpxchg() implementations 2015-10-15 00:21:13 +02:00
cputime.h cputime: Generic on-demand virtual cputime accounting 2013-01-27 19:23:27 +01:00
cputime_jiffies.h sched, time: Fix build error with 64 bit cputime_t on 32 bit systems 2014-10-03 05:46:55 +02:00
cputime_nsecs.h cputime: Prevent 32bit overflow in time[val|spec]_to_cputime() 2016-02-02 15:24:38 +01:00
current.h
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delay.h asm-generic: delay.h fix udelay and ndelay for 8 bit args 2011-07-22 18:45:33 +02:00
device.h
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div64.h __div64_32(): make it overridable at compile time 2015-11-16 14:42:12 -05:00
dma-contiguous.h asm-generic: Add dma-contiguous.h 2014-09-22 13:35:51 +02:00
dma.h
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early_ioremap.h Merge branch 'akpm' (patches from Andrew) 2015-09-08 17:52:23 -07:00
emergency-restart.h
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exec.h Split arch_align_stack() out from asm-generic/system.h 2012-03-28 18:30:03 +01:00
fb.h
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fixmap.h asm-generic: Fix local variable shadow in __set_fixmap_offset 2016-02-16 15:10:44 +00:00
ftrace.h
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futex.h asm-generic/futex: Re-enable preemption in futex_atomic_cmpxchg_inatomic() 2016-04-21 11:06:09 +02:00
getorder.h bitops: Add missing parentheses to new get_order macro 2012-02-24 10:39:27 -08:00
gpio.h gpio: allow setting ARCH_NR_GPIOS from Kconfig 2016-02-19 00:22:54 +01:00
hardirq.h
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hugetlb.h mm: Fix generic hugetlb pte check return type. 2013-10-02 20:02:35 -04:00
hw_irq.h
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ide_iops.h
…
int-ll64.h UAPI: (Scripted) Disintegrate include/asm-generic 2012-10-04 18:20:15 +01:00
io.h io-64-nonatomic: Add relaxed accessor variants 2016-05-03 18:23:02 +01:00
ioctl.h include/asm-generic/ioctl.h: fix _IOC_TYPECHECK sparse error 2014-06-06 16:08:13 -07:00
iomap.h x86/mm, asm-generic: Add ioremap_wt() for creating Write-Through mappings 2015-06-07 15:28:56 +02:00
irq.h
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irq_regs.h
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irq_work.h irq_work: Introduce arch_irq_work_has_interrupt() 2014-09-13 18:38:07 +02:00
irqflags.h
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kdebug.h
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kmap_types.h asm-generic: remove km_type definitions 2012-07-24 15:27:30 +08:00
kvm_para.h KVM: add kvm_para_available to asm-generic/kvm_para.h 2013-06-05 13:21:29 +03:00
libata-portmap.h
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linkage.h
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local.h atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
local64.h atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
mcs_spinlock.h locking/mcs: Allow architecture specific asm files to be used for contended case 2014-02-09 21:18:52 +01:00
memory_model.h mm: add PHYS_PFN, use it in __phys_to_pfn() 2016-01-14 16:00:49 -08:00
mm-arch-hooks.h mm: clean up per architecture MM hook header files 2015-07-17 16:39:53 -07:00
mm_hooks.h mm/core, x86/mm/pkeys: Differentiate instruction fetches 2016-02-18 19:46:29 +01:00
mmu.h asm-generic/mmu.h: Add support for FDPIC 2012-12-09 23:14:14 +01:00
mmu_context.h asm-generic: Remove asm-generic arch_bprm_mm_init() 2014-11-22 21:52:08 +01:00
module.h Make most arch asm/module.h files use asm-generic/module.h 2012-09-28 14:31:03 +09:30
msi.h asm-generic: Add msi.h 2014-11-23 13:01:47 +01:00
mutex-dec.h locking/mutex: Use acquire/release semantics 2015-10-06 17:28:20 +02:00
mutex-null.h arch: Make __mutex_fastpath_lock_retval return whether fastpath succeeded or not 2013-06-26 12:10:55 +02:00
mutex-xchg.h locking/mutex: Use acquire/release semantics 2015-10-06 17:28:20 +02:00
mutex.h
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page.h asm-generic: page.h: Remove useless get_user_page and free_user_page 2016-02-26 15:24:55 +01:00
param.h UAPI: (Scripted) Disintegrate include/asm-generic 2012-10-04 18:20:15 +01:00
parport.h include: remove __dev* attributes. 2013-01-03 15:57:16 -08:00
pci.h PCI: Remove unused pcibios_select_root() (again) 2015-06-08 07:56:21 -05:00
pci_iomap.h PCI: Add pci_iomap_wc() variants 2015-08-25 09:59:45 +02:00
percpu.h percpu: preffity percpu header files 2014-06-17 19:12:40 -04:00
pgalloc.h
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pgtable-nopmd.h
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pgtable-nopud.h
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pgtable.h arch: fix has_transparent_hugepage() 2016-05-19 19:12:14 -07:00
preempt.h sched/preempt: Fix preempt_count manipulations 2016-05-17 12:24:21 +02:00
ptrace.h asm-generic/ptrace.h: start a common low level ptrace helper 2011-05-26 17:12:36 -07:00
qrwlock.h locking/qrwlock: Make use of _{acquire|release|relaxed}() atomics 2015-08-12 11:59:06 +02:00
qrwlock_types.h locking/qrwlock: Rename ->lock to ->wait_lock 2015-09-18 09:27:29 +02:00
qspinlock.h locking/qspinlock: Fix spin_unlock_wait() some more 2016-06-08 14:29:08 +02:00
qspinlock_types.h locking/qspinlock: Move __ARCH_SPIN_LOCK_UNLOCKED to qspinlock_types.h 2016-02-29 10:02:43 +01:00
resource.h asm-generic: remove _STK_LIM_MAX 2014-05-15 00:32:09 +01:00
rtc.h rtc: cmos: century support 2015-09-05 13:19:09 +02:00
rwsem.h locking/rwsem: Introduce basis for down_write_killable() 2016-04-13 10:42:20 +02:00
seccomp.h seccomp: Get compat syscalls from asm-generic header 2016-05-13 14:02:00 +02:00
sections.h asm/sections: add helpers to check for section data 2016-01-16 11:17:24 -08:00
segment.h
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serial.h
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siginfo.h SIGNAL: Move generic copy_siginfo() to signal.h 2016-05-13 14:02:10 +02:00
signal.h unify default ptrace_signal_deliver 2012-11-29 00:01:23 -05:00
simd.h crypto: create generic version of ablk_helper 2013-09-24 06:02:24 +10:00
sizes.h ARM: 7430/1: sizes.h: move from asm-generic to <linux/sizes.h> 2012-06-28 17:14:34 +01:00
spinlock.h
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statfs.h UAPI: (Scripted) Disintegrate include/asm-generic 2012-10-04 18:20:15 +01:00
string.h
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switch_to.h Split the switch_to() wrapper out of asm-generic/system.h 2012-03-28 18:30:03 +01:00
syscall.h syscall.h: fix doc text for syscall_get_arch() 2014-09-23 16:20:00 -04:00
syscalls.h burying unused conditionals 2013-02-14 09:21:15 -05:00
termios-base.h
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termios.h UAPI: (Scripted) Disintegrate include/asm-generic 2012-10-04 18:20:15 +01:00
timex.h
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tlb.h treewide: Remove old email address 2015-11-23 09:44:58 +01:00
tlbflush.h BUG: headers with BUG/BUG_ON etc. need linux/bug.h 2012-03-04 17:54:34 -05:00
topology.h
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trace_clock.h tracing,x86: Add a TSC trace_clock 2012-11-13 15:48:27 -05:00
uaccess-unaligned.h
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uaccess.h asm-generic: {get,put}_user ptr argument evaluate only 1 time 2015-11-08 22:44:42 +09:00
unaligned.h asm-generic: allow generic unaligned access if the arch supports it 2014-05-08 10:22:23 +02:00
unistd.h We get rid of the general module prefix confusion with a binary config option, 2013-05-05 10:58:06 -07:00
user.h
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vga.h
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vmlinux.lds.h x86/asm: Make sure verify_cpu() has a good stack 2016-04-13 11:52:19 +02:00
vtime.h include/asm-generic/vtime.h: avoid zero-length file 2013-09-30 14:31:02 -07:00
word-at-a-time.h Make asm/word-at-a-time.h available on all architectures 2015-07-08 16:41:55 -04:00
xor.h asm-generic: xor: mark static functions as __maybe_unused 2012-10-03 21:21:06 +02:00