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
asm-offsets.h
atomic64.h
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
audit_change_attr.h
audit_dir_write.h
audit_read.h
audit_signal.h
audit_write.h
barrier.h
bitops.h
bitsperlong.h
bug.h	asm-generic changes for 4.6	2016-03-24 23:13:48 -07:00
bugs.h
cache.h
cacheflush.h
checksum.h	ipv4: Update parameters for csum_tcpudp_magic to their original types	2016-03-13 23:55:13 -04:00
clkdev.h
cmpxchg-local.h
cmpxchg.h
cputime_jiffies.h
cputime_nsecs.h
cputime.h
current.h
delay.h
device.h
div64.h
dma-contiguous.h
dma.h
early_ioremap.h
emergency-restart.h
exec.h
fb.h
fixmap.h
ftrace.h
futex.h	asm-generic/futex: Re-enable preemption in futex_atomic_cmpxchg_inatomic()	2016-04-21 11:06:09 +02:00
getorder.h
gpio.h
hardirq.h
hugetlb.h
hw_irq.h
ide_iops.h
int-ll64.h
io.h	io-64-nonatomic: Add relaxed accessor variants	2016-05-03 18:23:02 +01:00
ioctl.h
iomap.h
irq_regs.h
irq_work.h
irq.h
irqflags.h
Kbuild.asm
kdebug.h
kmap_types.h
kvm_para.h
libata-portmap.h
linkage.h
local64.h
local.h
mcs_spinlock.h
memory_model.h
mm_hooks.h
mm-arch-hooks.h
mmu_context.h
mmu.h
module.h
msi.h
mutex-dec.h
mutex-null.h
mutex-xchg.h
mutex.h
page.h
param.h
parport.h
pci_iomap.h
pci.h
percpu.h
pgalloc.h
pgtable-nopmd.h
pgtable-nopud.h
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
qrwlock_types.h
qrwlock.h
qspinlock_types.h	locking/qspinlock: Move __ARCH_SPIN_LOCK_UNLOCKED to qspinlock_types.h	2016-02-29 10:02:43 +01:00
qspinlock.h	locking/qspinlock: Fix spin_unlock_wait() some more	2016-06-08 14:29:08 +02:00
resource.h
rtc.h
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
segment.h
serial.h
siginfo.h	SIGNAL: Move generic copy_siginfo() to signal.h	2016-05-13 14:02:10 +02:00
signal.h
simd.h
sizes.h
spinlock.h
statfs.h
string.h
switch_to.h
syscall.h
syscalls.h
termios-base.h
termios.h
timex.h
tlb.h
tlbflush.h
topology.h
trace_clock.h
uaccess-unaligned.h
uaccess.h
unaligned.h
unistd.h
user.h
vga.h
vmlinux.lds.h	x86/asm: Make sure verify_cpu() has a good stack	2016-04-13 11:52:19 +02:00
vtime.h
word-at-a-time.h
xor.h