linux.git/kernel/rcu/tree.c, branch v4.15

Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2017-11-13T20:38:26+00:00

Pull core locking updates from Ingo Molnar:
 "The main changes in this cycle are:

   - Another attempt at enabling cross-release lockdep dependency
     tracking (automatically part of CONFIG_PROVE_LOCKING=y), this time
     with better performance and fewer false positives. (Byungchul Park)

   - Introduce lockdep_assert_irqs_enabled()/disabled() and convert
     open-coded equivalents to lockdep variants. (Frederic Weisbecker)

   - Add down_read_killable() and use it in the VFS's iterate_dir()
     method. (Kirill Tkhai)

   - Convert remaining uses of ACCESS_ONCE() to
     READ_ONCE()/WRITE_ONCE(). Most of the conversion was Coccinelle
     driven. (Mark Rutland, Paul E. McKenney)

   - Get rid of lockless_dereference(), by strengthening Alpha atomics,
     strengthening READ_ONCE() with smp_read_barrier_depends() and thus
     being able to convert users of lockless_dereference() to
     READ_ONCE(). (Will Deacon)

   - Various micro-optimizations:

        - better PV qspinlocks (Waiman Long),
        - better x86 barriers (Michael S. Tsirkin)
        - better x86 refcounts (Kees Cook)

   - ... plus other fixes and enhancements. (Borislav Petkov, Juergen
     Gross, Miguel Bernal Marin)"

* 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
  locking/x86: Use LOCK ADD for smp_mb() instead of MFENCE
  rcu: Use lockdep to assert IRQs are disabled/enabled
  netpoll: Use lockdep to assert IRQs are disabled/enabled
  timers/posix-cpu-timers: Use lockdep to assert IRQs are disabled/enabled
  sched/clock, sched/cputime: Use lockdep to assert IRQs are disabled/enabled
  irq_work: Use lockdep to assert IRQs are disabled/enabled
  irq/timings: Use lockdep to assert IRQs are disabled/enabled
  perf/core: Use lockdep to assert IRQs are disabled/enabled
  x86: Use lockdep to assert IRQs are disabled/enabled
  smp/core: Use lockdep to assert IRQs are disabled/enabled
  timers/hrtimer: Use lockdep to assert IRQs are disabled/enabled
  timers/nohz: Use lockdep to assert IRQs are disabled/enabled
  workqueue: Use lockdep to assert IRQs are disabled/enabled
  irq/softirqs: Use lockdep to assert IRQs are disabled/enabled
  locking/lockdep: Add IRQs disabled/enabled assertion APIs: lockdep_assert_irqs_enabled()/disabled()
  locking/pvqspinlock: Implement hybrid PV queued/unfair locks
  locking/rwlocks: Fix comments
  x86/paravirt: Set up the virt_spin_lock_key after static keys get initialized
  block, locking/lockdep: Assign a lock_class per gendisk used for wait_for_completion()
  workqueue: Remove now redundant lock acquisitions wrt. workqueue flushes
  ...

rcu: Use lockdep to assert IRQs are disabled/enabled

2017-11-08T10:13:55+00:00

Lockdep now has an integrated IRQs disabled/enabled sanity check. Just
use it instead of the ad-hoc RCU version.

Signed-off-by: Frederic Weisbecker 
Acked-by: Thomas Gleixner 
Acked-by: Paul E. McKenney 
Cc: David S . Miller 
Cc: Lai Jiangshan 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Tejun Heo 
Link: http://lkml.kernel.org/r/1509980490-4285-15-git-send-email-frederic@kernel.org
Signed-off-by: Ingo Molnar

Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

2017-10-24T08:49:44+00:00

Pull RCU updates from Paul E. McKenney:

 - Documentation updates
 - Miscellaneous fixes
 - RCU CPU stall-warning updates
 - Torture-test updates

Signed-off-by: Ingo Molnar

Merge branches 'doc.2017.10.20a', 'fixes.2017.10.19a', 'stall.2017.10.09a' and 'torture.2017.10.09a' into HEAD

2017-10-20T18:11:15+00:00

doc.2017.10.20a: Documentation updates.
fixes.2017.10.19a: Miscellaneous fixes.
stall.2017.10.09a: RCU CPU stall-warning updates.
torture.2017.10.09a: Torture-test updates.

doc: Fix various RCU docbook comment-header problems

2017-10-20T02:26:11+00:00

Because many of RCU's files have not been included into docbook, a
number of errors have accumulated.  This commit fixes them.

Signed-off-by: Paul E. McKenney 
Signed-off-by: Linus Torvalds

rcu: Add extended-quiescent-state testing advice

2017-10-19T19:13:36+00:00

If you add or remove calls to rcu_idle_enter(), rcu_user_enter(),
rcu_irq_exit(), rcu_irq_exit_irqson(), rcu_idle_exit(), rcu_user_exit(),
rcu_irq_enter(), rcu_irq_enter_irqson(), rcu_nmi_enter(), or
rcu_nmi_exit(), you should run a full set of tests on a kernel built
with CONFIG_RCU_EQS_DEBUG=y.

Signed-off-by: Paul E. McKenney

rcu: Make RCU CPU stall warnings check for irq-disabled CPUs

2017-10-09T21:25:17+00:00

One common question upon seeing an RCU CPU stall warning is "did
the stalled CPUs have interrupts disabled?"  However, the current
stall warnings are silent on this point.  This commit therefore
uses irq_work to check whether stalled CPUs still respond to IPIs,
and flags this state in the RCU CPU stall warning console messages.

Reported-by: Steven Rostedt 
Signed-off-by: Paul E. McKenney

sched,rcu: Make cond_resched() provide RCU quiescent state

2017-10-09T21:25:17+00:00

There is some confusion as to which of cond_resched() or
cond_resched_rcu_qs() should be added to long in-kernel loops.
This commit therefore eliminates the decision by adding RCU quiescent
states to cond_resched().  This commit also simplifies the code that
used to interact with cond_resched_rcu_qs(), and that now interacts with
cond_resched(), to reduce its overhead.  This reduction is necessary to
allow the heavier-weight cond_resched_rcu_qs() mechanism to be invoked
everywhere that cond_resched() is invoked.

Part of that reduction in overhead converts the jiffies_till_sched_qs
kernel parameter to read-only at runtime, thus eliminating the need for
bounds checking.

Reported-by: Michal Hocko 
Signed-off-by: Paul E. McKenney 
Cc: Peter Zijlstra 
[ paulmck: Keep PREEMPT=n cond_resched a no-op, per Peter Zijlstra. ]

Merge tag 'trace-v4.14-rc1-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

2017-10-04T15:34:01+00:00

Pull tracing fixlets from Steven Rostedt:
 "Two updates:

   - A memory fix with left over code from spliting out ftrace_ops and
     function graph tracer, where the function graph tracer could reset
     the trampoline pointer, leaving the old trampoline not to be freed
     (memory leak).

   - The update to Paul's patch that added the unnecessary READ_ONCE().
     This removes the unnecessary READ_ONCE() instead of having to
     rebase the branch to update the patch that added it"

* tag 'trace-v4.14-rc1-3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  rcu: Remove extraneous READ_ONCE()s from rcu_irq_{enter,exit}()
  ftrace: Fix kmemleak in unregister_ftrace_graph

rcu: Remove extraneous READ_ONCE()s from rcu_irq_{enter,exit}()

2017-10-03T14:27:32+00:00

The read of ->dynticks_nmi_nesting in rcu_irq_enter() and rcu_irq_exit()
is currently protected with READ_ONCE().  However, this protection is
unnecessary because (1) ->dynticks_nmi_nesting is updated only by the
current CPU, (2) Although NMI handlers can update this field, they reset
it back to its old value before return, and (3) Interrupts are disabled,
so nothing else can modify it.  The value of ->dynticks_nmi_nesting is
thus effectively constant, and so no protection is required.

This commit therefore removes the READ_ONCE() protection from these
two accesses.

Link: http://lkml.kernel.org/r/20170926031902.GA2074@linux.vnet.ibm.com

Reported-by: Linus Torvalds 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Steven Rostedt (VMware)