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Will Deacon 6b4f4bc9cb locking/futex: Allow low-level atomic operations to return -EAGAIN 
Some futex() operations, including FUTEX_WAKE_OP, require the kernel to
perform an atomic read-modify-write of the futex word via the userspace
mapping. These operations are implemented by each architecture in
arch_futex_atomic_op_inuser() and futex_atomic_cmpxchg_inatomic(), which
are called in atomic context with the relevant hash bucket locks held.

Although these routines may return -EFAULT in response to a page fault
generated when accessing userspace, they are expected to succeed (i.e.
return 0) in all other cases. This poses a problem for architectures
that do not provide bounded forward progress guarantees or fairness of
contended atomic operations and can lead to starvation in some cases.

In these problematic scenarios, we must return back to the core futex
code so that we can drop the hash bucket locks and reschedule if
necessary, much like we do in the case of a page fault.

Allow architectures to return -EAGAIN from their implementations of
arch_futex_atomic_op_inuser() and futex_atomic_cmpxchg_inatomic(), which
will cause the core futex code to reschedule if necessary and return
back to the architecture code later on.

Cc: <stable@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
 		2019-04-26 13:57:31 +01:00
..
bpf bpf: verifier: propagate liveness on all frames 2019-03-21 19:57:02 -07:00
cgroup Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
configs kvm_config: add CONFIG_VIRTIO_MENU 2018-10-24 20:55:56 -04:00
debug kdb: use bool for binary state indicators 2018-12-30 08:31:52 +00:00
dma memblock: drop memblock_alloc_*_nopanic() variants 2019-03-12 10:04:02 -07:00
events perf/core improvements and fixes: 2019-03-22 22:50:41 +01:00
gcov kernel/gcov/gcc_3_4.c: use struct_size() in kzalloc() 2019-03-07 18:32:02 -08:00
irq genirq: Mark expected switch case fall-through 2019-03-23 12:32:01 +01:00
livepatch Merge branch 'for-5.1/atomic-replace' into for-linus 2019-03-05 15:56:59 +01:00
locking locking/lockdep: Only call init_rcu_head() after RCU has been initialized 2019-03-09 14:15:51 +01:00
power treewide: add checks for the return value of memblock_alloc*() 2019-03-12 10:04:02 -07:00
printk fbdev changes for v5.1: 2019-03-15 14:22:59 -07:00
rcu Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-03-06 07:59:36 -08:00
sched Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-03-24 11:42:10 -07:00
time time/jiffies: Make refined_jiffies static 2019-03-22 13:38:26 +01:00
trace ftrace: Fix warning using plain integer as NULL & spelling corrections 2019-03-26 08:35:36 -04:00
.gitignore kernel/configs: use .incbin directive to embed config_data.gz 2019-03-07 18:32:02 -08:00
Kconfig.freezer
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Kconfig.hz
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Kconfig.locks bpf: introduce bpf_spin_lock 2019-02-01 20:55:38 +01:00
Kconfig.preempt kconfig: warn no new line at end of file 2018-12-15 17:44:35 +09:00
Makefile kernel/configs: use .incbin directive to embed config_data.gz 2019-03-07 18:32:02 -08:00
acct.c
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async.c async: Add support for queueing on specific NUMA node 2019-01-31 14:20:54 +01:00
audit.c audit: remove audit_context when CONFIG_ AUDIT and not AUDITSYSCALL 2019-02-03 17:49:35 -05:00
audit.h audit: hide auditsc_get_stamp and audit_serial prototypes 2019-02-07 21:44:27 -05:00
audit_fsnotify.c audit: add syscall information to CONFIG_CHANGE records 2019-01-18 17:53:29 -05:00
audit_tree.c audit: hand taken context to audit_kill_trees for syscall logging 2019-01-14 18:01:05 -05:00
audit_watch.c audit: add syscall information to CONFIG_CHANGE records 2019-01-18 17:53:29 -05:00
auditfilter.c audit: mark expected switch fall-through 2019-02-12 20:17:13 -05:00
auditsc.c audit: remove audit_context when CONFIG_ AUDIT and not AUDITSYSCALL 2019-02-03 17:49:35 -05:00
backtracetest.c
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bounds.c kbuild: fix kernel/bounds.c 'W=1' warning 2018-10-31 08:54:14 -07:00
capability.c LSM: add SafeSetID module that gates setid calls 2019-01-25 11:22:43 -08:00
compat.c time: make adjtime compat handling available for 32 bit 2019-02-07 00:13:27 +01:00
configs.c kernel/configs: use .incbin directive to embed config_data.gz 2019-03-07 18:32:02 -08:00
context_tracking.c
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cpu.c cpu/hotplug: Prevent crash when CPU bringup fails on CONFIG_HOTPLUG_CPU=n 2019-03-28 13:34:58 +01:00
cpu_pm.c
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crash_core.c kexec: export PG_offline to VMCOREINFO 2019-03-05 21:07:14 -08:00
crash_dump.c
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cred.c SELinux: Remove cred security blob poisoning 2019-01-08 13:18:44 -08:00
delayacct.c delayacct: track delays from thrashing cache pages 2018-10-26 16:26:32 -07:00
dma.c
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elfcore.c
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exec_domain.c
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exit.c Merge branch 'for-5.1' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2019-03-07 10:11:41 -08:00
extable.c
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fail_function.c kernel/fail_function.c: remove meaningless null pointer check before debugfs_remove_recursive 2018-10-31 08:54:12 -07:00
fork.c 5.1 Merge Window Pull Request 2019-03-09 15:53:03 -08:00
freezer.c PM / reboot: Eliminate race between reboot and suspend 2018-08-06 12:35:20 +02:00
futex.c locking/futex: Allow low-level atomic operations to return -EAGAIN 2019-04-26 13:57:31 +01:00
groups.c
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hung_task.c kernel/hung_task.c: Use continuously blocked time when reporting. 2019-03-07 18:31:59 -08:00
iomem.c
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irq_work.c
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jump_label.c jump_label: move 'asm goto' support test to Kconfig 2019-01-06 09:46:51 +09:00
kallsyms.c bpf: Add module name [bpf] to ksymbols for bpf programs 2019-01-21 17:38:56 -03:00
kcmp.c
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kcov.c kcov: convert kcov.refcount to refcount_t 2019-03-07 18:32:02 -08:00
kexec.c
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kexec_core.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
kexec_file.c kexec_file: kexec_walk_memblock() only walks a dedicated region at kdump 2018-12-06 14:38:50 +00:00
kexec_internal.h
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kmod.c
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kprobes.c kprobes: Search non-suffixed symbol in blacklist 2019-02-13 08:16:40 +01:00
ksysfs.c
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kthread.c Merge branch 'akpm' (patches from Andrew) 2019-03-06 10:31:36 -08:00
latencytop.c
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memremap.c mm/hmm: fix memremap.h, move dev_page_fault_t callback to hmm 2018-12-28 12:11:52 -08:00
module-internal.h
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module.c dynamic_debug: add static inline stub for ddebug_add_module 2019-03-07 18:32:00 -08:00
module_signing.c modsign: use all trusted keys to verify module signature 2018-11-07 14:41:41 +01:00
notifier.c
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nsproxy.c
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padata.c padata: clean an indentation issue, remove extraneous space 2018-11-16 14:11:04 +08:00
panic.c kernel/panic.c: taint: fix debugfs_simple_attr.cocci warnings 2019-03-07 18:31:59 -08:00
params.c
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pid.c Fix failure path in alloc_pid() 2018-12-28 12:42:30 -08:00
pid_namespace.c signal: Use group_send_sig_info to kill all processes in a pid namespace 2018-09-16 16:08:25 +02:00
profile.c mm: remove include/linux/bootmem.h 2018-10-31 08:54:16 -07:00
ptrace.c ptrace: take into account saved_sigmask in PTRACE{GET,SET}SIGMASK 2019-03-29 10:01:37 -07:00
range.c
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reboot.c kernel/reboot.c: export pm_power_off_prepare 2018-09-11 16:13:24 +01:00
relay.c Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 13:27:20 -07:00
resource.c device-dax for 5.1 2019-03-16 13:05:32 -07:00
rseq.c Remove 'type' argument from access_ok() function 2019-01-03 18:57:57 -08:00
seccomp.c Merge branch 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2019-03-07 11:44:01 -08:00
signal.c pidfd patches for v5.1-rc1 2019-03-16 13:47:14 -07:00
smp.c cpu/hotplug: Fix "SMT disabled by BIOS" detection for KVM 2019-01-30 19:27:00 +01:00
smpboot.c
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smpboot.h
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softirq.c softirq: Don't skip softirq execution when softirq thread is parking 2019-02-10 21:51:39 +01:00
stackleak.c stackleak: Mark stackleak_track_stack() as notrace 2018-12-05 19:31:44 -08:00
stacktrace.c
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stop_machine.c Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-08-13 11:25:07 -07:00
sys.c Merge branch 'akpm' (patches from Andrew) 2019-03-07 19:25:37 -08:00
sys_ni.c pidfd patches for v5.1-rc1 2019-03-16 13:47:14 -07:00
sysctl.c kernel/sysctl.c: define minmax conv functions in terms of non-minmax versions 2019-03-12 10:04:00 -07:00
sysctl_binary.c kernel/sysctl: add panic_print into sysctl 2019-01-04 13:13:47 -08:00
task_work.c
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taskstats.c
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test_kprobes.c
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torture.c Merge branches 'doc.2019.01.26a', 'fixes.2019.01.26a', 'sil.2019.01.26a', 'spdx.2019.02.09a', 'srcu.2019.01.26a' and 'torture.2019.01.26a' into HEAD 2019-02-09 08:47:52 -08:00
tracepoint.c tracing: Replace synchronize_sched() and call_rcu_sched() 2018-11-27 09:21:41 -08:00
tsacct.c
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ucount.c
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uid16.c
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uid16.h
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umh.c umh: add exit routine for UMH process 2019-01-11 18:05:40 -08:00
up.c smp,cpumask: introduce on_each_cpu_cond_mask 2018-10-09 16:51:11 +02:00
user-return-notifier.c
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user.c userns: use irqsave variant of refcount_dec_and_lock() 2018-08-22 10:52:47 -07:00
user_namespace.c userns: also map extents in the reverse map to kernel IDs 2018-11-07 23:51:16 -06:00
utsname.c
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utsname_sysctl.c sys: don't hold uts_sem while accessing userspace memory 2018-08-11 02:05:53 -05:00
watchdog.c watchdog: Respect watchdog cpumask on CPU hotplug 2019-03-28 13:32:01 +01:00
watchdog_hld.c watchdog: Mark watchdog touch functions as notrace 2018-08-30 12:56:40 +02:00
workqueue.c workqueue: Only unregister a registered lockdep key 2019-03-21 12:00:18 +01:00
workqueue_internal.h psi: fix aggregation idle shut-off 2019-02-01 15:46:23 -08:00