Peter Zijlstra 56222b212e futex: Drop hb->lock before enqueueing on the rtmutex ... When PREEMPT_RT_FULL does the spinlock -> rt_mutex substitution the PI chain code will (falsely) report a deadlock and BUG. The problem is that it hold hb->lock (now an rt_mutex) while doing task_blocks_on_rt_mutex on the futex's pi_state::rtmutex. This, when interleaved just right with futex_unlock_pi() leads it to believe to see an AB-BA deadlock. Task1 (holds rt_mutex, Task2 (does FUTEX_LOCK_PI) does FUTEX_UNLOCK_PI) lock hb->lock lock rt_mutex (as per start_proxy) lock hb->lock Which is a trivial AB-BA. It is not an actual deadlock, because it won't be holding hb->lock by the time it actually blocks on the rt_mutex, but the chainwalk code doesn't know that and it would be a nightmare to handle this gracefully. To avoid this problem, do the same as in futex_unlock_pi() and drop hb->lock after acquiring wait_lock. This still fully serializes against futex_unlock_pi(), since adding to the wait_list does the very same lock dance, and removing it holds both locks. Aside of solving the RT problem this makes the lock and unlock mechanism symetric and reduces the hb->lock held time. Reported-and-tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: juri.lelli@arm.com Cc: xlpang@redhat.com Cc: rostedt@goodmis.org Cc: mathieu.desnoyers@efficios.com Cc: jdesfossez@efficios.com Cc: dvhart@infradead.org Cc: bristot@redhat.com Link: http://lkml.kernel.org/r/20170322104152.161341537@infradead.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>		2017-03-23 19:14:59 +01:00
..
bpf	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2017-03-04 17:31:39 -08:00
cgroup	scripts/spelling.txt: add "disble(d)" pattern and fix typo instances	2017-03-09 17:01:09 -08:00
configs	config: android-base: enable hardened usercopy and kernel ASLR	2017-02-27 18:43:46 -08:00
debug	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>	2017-03-02 08:42:34 +01:00
events	scripts/spelling.txt: add "disble(d)" pattern and fix typo instances	2017-03-09 17:01:09 -08:00
gcov
irq	sched/headers: Prepare to move the get_task_struct()/put_task_struct() and related APIs from <linux/sched.h> to <linux/sched/task.h>	2017-03-02 08:42:40 +01:00
livepatch
locking	futex: Drop hb->lock before enqueueing on the rtmutex	2017-03-23 19:14:59 +01:00
power	Merge branch 'WIP.sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-03-03 10:16:38 -08:00
printk	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h>	2017-03-02 08:42:36 +01:00
rcu	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>	2017-03-02 08:42:34 +01:00
sched	Power management updates for v4.11-rc2	2017-03-09 16:30:37 -08:00
time	Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-03-07 14:45:22 -08:00
trace	scripts/spelling.txt: add "overide" pattern and fix typo instances	2017-03-09 17:01:09 -08:00
.gitignore
acct.c	sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h>	2017-03-02 08:42:39 +01:00
async.c
audit_fsnotify.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2016-12-17 18:44:00 -08:00
audit_tree.c	Merge branch 'stable-4.10' of git://git.infradead.org/users/pcmoore/audit	2017-01-05 23:06:06 -08:00
audit_watch.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2016-12-17 18:44:00 -08:00
audit.c	Merge branch 'stable-4.11' of git://git.infradead.org/users/pcmoore/audit	2017-02-21 13:25:50 -08:00
audit.h	Merge branch 'stable-4.11' of git://git.infradead.org/users/pcmoore/audit	2017-02-21 13:25:50 -08:00
auditfilter.c	audit: add support for session ID user filter	2016-11-29 15:10:12 -05:00
auditsc.c	Merge branch 'stable-4.11' of git://git.infradead.org/users/pcmoore/audit	2017-02-21 13:25:50 -08:00
backtracetest.c
bounds.c
capability.c	capability: export has_capability	2017-01-12 07:01:56 -07:00
compat.c	Replace <asm/uaccess.h> with <linux/uaccess.h> globally	2016-12-24 11:46:01 -08:00
configs.c	Replace <asm/uaccess.h> with <linux/uaccess.h> globally	2016-12-24 11:46:01 -08:00
context_tracking.c
cpu_pm.c
cpu.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h>	2017-03-02 08:42:35 +01:00
crash_dump.c
cred.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/coredump.h>	2017-03-02 08:42:28 +01:00
delayacct.c	sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h>	2017-03-02 08:42:39 +01:00
dma.c
elfcore.c
exec_domain.c
exit.c	userfaultfd: non-cooperative: rollback userfaultfd_exit	2017-03-09 17:01:09 -08:00
extable.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next	2017-02-22 10:15:09 -08:00
fork.c	sched/headers, RCU: Move rcu_copy_process() from <linux/sched/task.h> to kernel/fork.c	2017-03-03 01:43:46 +01:00
freezer.c
futex_compat.c	Replace <asm/uaccess.h> with <linux/uaccess.h> globally	2016-12-24 11:46:01 -08:00
futex.c	futex: Drop hb->lock before enqueueing on the rtmutex	2017-03-23 19:14:59 +01:00
groups.c	Replace <asm/uaccess.h> with <linux/uaccess.h> globally	2016-12-24 11:46:01 -08:00
hung_task.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>	2017-03-02 08:42:34 +01:00
irq_work.c
jump_label.c	This release has no new tracing features, just clean ups, minor fixes	2017-02-27 13:26:17 -08:00
kallsyms.c	bpf: make jited programs visible in traces	2017-02-17 13:40:05 -05:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks	locking/mutex: Allow MUTEX_SPIN_ON_OWNER when DEBUG_MUTEXES	2016-10-25 11:31:51 +02:00
Kconfig.preempt
kcov.c	kcov: make kcov work properly with KASLR enabled	2016-12-20 09:48:47 -08:00
kexec_core.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk	2017-02-22 17:33:34 -08:00
kexec_file.c	kexec, x86/purgatory: Unbreak it and clean it up	2017-03-10 20:55:09 +01:00
kexec_internal.h	kexec, x86/purgatory: Unbreak it and clean it up	2017-03-10 20:55:09 +01:00
kexec.c
kmod.c	sched/headers, vfs/execve: Prepare to move the do_execve*() prototypes from <linux/sched.h> to <linux/binfmts.h>	2017-03-02 08:42:39 +01:00
kprobes.c	powerpc updates for 4.11 part 1.	2017-02-22 10:30:38 -08:00
ksysfs.c	kernel/ksysfs.c: add __ro_after_init to bin_attribute structure	2017-02-24 17:46:56 -08:00
kthread.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h>	2017-03-02 08:42:35 +01:00
latencytop.c	sched/headers: Prepare to move sched_info_on() and force_schedstat_enabled() from <linux/sched.h> to <linux/sched/stat.h>	2017-03-02 08:42:39 +01:00
Makefile	cgroup: move cgroup files under kernel/cgroup/	2016-12-27 14:49:05 -05:00
membarrier.c	Fix: Disable sys_membarrier when nohz_full is enabled	2017-01-23 11:32:16 -08:00
memremap.c	mm, devm_memremap_pages: hold device_hotplug lock over mem_hotplug_{begin, done}	2017-02-24 17:46:53 -08:00
module_signing.c
module-internal.h
module.c	locking/lockdep: Handle statically initialized PER_CPU locks properly	2017-03-16 09:57:08 +01:00
notifier.c	kernel/notifier.c: simplify expression	2017-02-24 17:46:56 -08:00
nsproxy.c
padata.c	padata: Remove unused but set variables	2016-10-25 11:08:10 +08:00
panic.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>	2017-03-02 08:42:34 +01:00
params.c
pid_namespace.c	sched/headers: Prepare for the reduction of <linux/sched.h>'s signal API dependency	2017-03-02 08:42:37 +01:00
pid.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h>	2017-03-02 08:42:35 +01:00
profile.c	sched/headers: Prepare to move sched_info_on() and force_schedstat_enabled() from <linux/sched.h> to <linux/sched/stat.h>	2017-03-02 08:42:39 +01:00
ptrace.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h>	2017-03-02 08:42:35 +01:00
range.c
reboot.c
relay.c	lib/vsprintf.c: remove %Z support	2017-02-27 18:43:47 -08:00
resource.c
seccomp.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task_stack.h>	2017-03-02 08:42:36 +01:00
signal.c	sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h>	2017-03-02 08:42:39 +01:00
smp.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/idle.h>	2017-03-02 08:42:26 +01:00
smpboot.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h>	2017-03-02 08:42:35 +01:00
smpboot.h
softirq.c	softirq: Display IRQ_POLL for irq-poll statistics	2016-10-21 15:45:47 -06:00
stacktrace.c	stacktrace, lockdep: Fix address, newline ugliness	2017-02-08 08:21:31 +01:00
stop_machine.c	locking/core, stop_machine: Yield the CPU during stop machine()	2016-11-16 10:15:09 +01:00
sys_ni.c	move aio compat to fs/aio.c	2016-12-22 22:58:37 -05:00
sys.c	sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h>	2017-03-02 08:42:39 +01:00
sysctl_binary.c	sysctl: add KERN_CONT to deprecated_sysctl_warning()	2016-12-14 16:04:07 -08:00
sysctl.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/coredump.h>	2017-03-02 08:42:28 +01:00
task_work.c
taskstats.c	Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net	2016-11-15 10:54:36 -05:00
test_kprobes.c
torture.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/clock.h>	2017-03-02 08:42:27 +01:00
tracepoint.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/task.h>	2017-03-02 08:42:35 +01:00
tsacct.c	sched/headers: Prepare to move cputime functionality from <linux/sched.h> into <linux/sched/cputime.h>	2017-03-02 08:42:39 +01:00
ucount.c	ucount: Remove the atomicity from ucount->count	2017-03-06 15:26:37 -06:00
uid16.c	sched/headers: Prepare to remove <linux/cred.h> inclusion from <linux/sched.h>	2017-03-02 08:42:31 +01:00
up.c	smp: Add function to execute a function synchronously on a CPU	2016-09-05 13:52:39 +02:00
user_namespace.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/signal.h>	2017-03-02 08:42:29 +01:00
user-return-notifier.c
user.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/user.h>	2017-03-02 08:42:29 +01:00
utsname_sysctl.c	sched/headers: Remove <linux/rwsem.h> from <linux/sched.h>	2017-03-03 01:45:36 +01:00
utsname.c	sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h>	2017-03-02 08:42:38 +01:00
watchdog_hld.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>	2017-03-02 08:42:34 +01:00
watchdog.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/debug.h>	2017-03-02 08:42:34 +01:00
workqueue_internal.h
workqueue.c	time: Remove CONFIG_TIMER_STATS	2017-02-10 11:15:08 +01:00