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
..
acpi	libnvdimm for 4.7	2016-05-23 11:18:01 -07:00
asm-generic	locking/qspinlock: Fix spin_unlock_wait() some more	2016-06-08 14:29:08 +02:00
clocksource	clocksource: arm_arch_timer: Remove arch_timer_get_timecounter	2016-05-03 12:54:21 +02:00
crypto	Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security	2016-05-19 09:21:36 -07:00
drm	Merge tag 'drm-intel-next-fixes-2016-05-25' of git://anongit.freedesktop.org/drm-intel into drm-next	2016-05-27 16:08:38 +10:00
dt-bindings	Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/rzhang/linux	2016-05-26 09:23:43 -07:00
keys
kvm	KVM: arm/arm64: vgic-new: implement mapped IRQ handling	2016-05-20 15:40:09 +02:00
linux	locking/seqcount: Re-fix raw_read_seqcount_latch()	2016-06-03 08:37:25 +02:00
math-emu
media	[media] media: rc: reduce size of struct ir_raw_event	2016-05-07 10:34:17 -03:00
memory
misc	cxl: Add kernel API to allow a context to operate with relocate disabled	2016-05-11 21:54:10 +10:00
net	ipv6: hide ip6_encap_hlen/ip6_tnl_encap definitions	2016-05-29 22:24:21 -07:00
pcmcia
ras
rdma	IB/core: Make device counter infrastructure dynamic	2016-05-26 12:52:51 -04:00
rxrpc
scsi	Merge branch '4.7/scsi-queue' of git://git.kernel.org/pub/scm/linux/kernel/git/mkp/scsi into for-4.7-zac	2016-05-09 12:34:39 -04:00
soc	ARC updates for 4.7-rc1	2016-05-19 09:46:18 -07:00
sound	ASoC: Updates for v4.7	2016-05-16 14:59:00 +02:00
target	Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending	2016-05-28 12:04:17 -07:00
trace	- move kvm_stat tool from QEMU repo into tools/kvm/kvm_stat	2016-05-27 13:41:54 -07:00
uapi	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2016-05-31 22:28:28 -07:00
video	imx-drm probing fix	2016-05-25 12:36:20 +10:00
xen
Kbuild