linux/kernel/time/Kconfig, branch v3.13

nohz: Drop generic vtime obsolete dependency on CONFIG_64BIT

2013-09-30T13:37:01Z

The CONFIG_64BIT requirement on vtime can finally be removed since we now depend on HAVE_VIRT_CPU_ACCOUNTING_GEN which already takes care of the arch ability to handle nsecs based cputime_t safely. Signed-off-by: Kevin Hilman Cc: Ingo Molnar Cc: Russell King Cc: Paul E. McKenney Cc: Arm Linux Signed-off-by: Frederic Weisbecker

vtime: Add HAVE_VIRT_CPU_ACCOUNTING_GEN Kconfig

2013-09-30T13:35:53Z

With VIRT_CPU_ACCOUNTING_GEN, cputime_t becomes 64-bit. In order to use that feature, arch code should be audited to ensure there are no races in concurrent read/write of cputime_t. For example, reading/writing 64-bit cputime_t on some 32-bit arches may require multiple accesses for low and high value parts, so proper locking is needed to protect against concurrent accesses. Therefore, add CONFIG_HAVE_VIRT_CPU_ACCOUNTING_GEN which arches can enable after they've been audited for potential races. This option is automatically enabled on 64-bit platforms. Feature requested by Frederic Weisbecker. Signed-off-by: Kevin Hilman Cc: Ingo Molnar Cc: Russell King Cc: Paul E. McKenney Cc: Arm Linux Signed-off-by: Frederic Weisbecker

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

2013-09-04T16:36:54Z

Pull timers/nohz changes from Ingo Molnar: "It mostly contains fixes and full dynticks off-case optimizations, by Frederic Weisbecker" * 'timers-nohz-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits) nohz: Include local CPU in full dynticks global kick nohz: Optimize full dynticks's sched hooks with static keys nohz: Optimize full dynticks state checks with static keys nohz: Rename a few state variables vtime: Always debug check snapshot source _before_ updating it vtime: Always scale generic vtime accounting results vtime: Optimize full dynticks accounting off case with static keys vtime: Describe overriden functions in dedicated arch headers m68k: hardirq_count() only need preempt_mask.h hardirq: Split preempt count mask definitions context_tracking: Split low level state headers vtime: Fix racy cputime delta update vtime: Remove a few unneeded generic vtime state checks context_tracking: User/kernel broundary cross trace events context_tracking: Optimize context switch off case with static keys context_tracking: Optimize guest APIs off case with static key context_tracking: Optimize main APIs off case with static key context_tracking: Ground setup for static key use context_tracking: Remove full dynticks' hacky dependency on wide context tracking nohz: Only enable context tracking on full dynticks CPUs ...

nohz_full: Add full-system-idle state machine

2013-08-31T21:43:50Z

This commit adds the state machine that takes the per-CPU idle data as input and produces a full-system-idle indication as output. This state machine is driven out of RCU's quiescent-state-forcing mechanism, which invokes rcu_sysidle_check_cpu() to collect per-CPU idle state and then rcu_sysidle_report() to drive the state machine. The full-system-idle state is sampled using rcu_sys_is_idle(), which also drives the state machine if RCU is idle (and does so by forcing RCU to become non-idle). This function returns true if all but the timekeeping CPU (tick_do_timer_cpu) are idle and have been idle long enough to avoid memory contention on the full_sysidle_state state variable. The rcu_sysidle_force_exit() may be called externally to reset the state machine back into non-idle state. For large systems the state machine is driven out of RCU's force-quiescent-state logic, which provides good scalability at the price of millisecond-scale latencies on the transition to full-system-idle state. This is not so good for battery-powered systems, which are usually small enough that they don't need to care about scalability, but which do care deeply about energy efficiency. Small systems therefore drive the state machine directly out of the idle-entry code. The number of CPUs in a "small" system is defined by a new NO_HZ_FULL_SYSIDLE_SMALL Kconfig parameter, which defaults to 8. Note that this is a build-time definition. Signed-off-by: Paul E. McKenney Cc: Frederic Weisbecker Cc: Steven Rostedt Cc: Lai Jiangshan [ paulmck: Use true and false for boolean constants per Lai Jiangshan. ] Reviewed-by: Josh Triplett [ paulmck: Simplify logic and provide better comments for memory barriers, based on review comments and questions by Lai Jiangshan. ]

nohz_full: Add Kconfig parameter for scalable detection of all-idle state

2013-08-19T01:07:02Z

At least one CPU must keep the scheduling-clock tick running for timekeeping purposes whenever there is a non-idle CPU. However, with the new nohz_full adaptive-idle machinery, it is difficult to distinguish between all CPUs really being idle as opposed to all non-idle CPUs being in adaptive-ticks mode. This commit therefore adds a Kconfig parameter as a first step towards enabling a scalable detection of full-system idle state. Signed-off-by: Paul E. McKenney Cc: Frederic Weisbecker Cc: Steven Rostedt [ paulmck: Update help text per Frederic Weisbecker. ] Reviewed-by: Josh Triplett

context_tracking: Remove full dynticks' hacky dependency on wide context tracking

2013-08-12T22:54:34Z

Now that the full dynticks subsystem only enables the context tracking on full dynticks CPUs, lets remove the dependency on CONTEXT_TRACKING_FORCE This dependency was a hack to enable the context tracking widely for the full dynticks susbsystem until the latter becomes able to enable it in a more CPU-finegrained fashion. Now CONTEXT_TRACKING_FORCE only stands for testing on archs that work on support for the context tracking while full dynticks can't be used yet due to unmet dependencies. It simulates a system where all CPUs are full dynticks so that RCU user extended quiescent states and dynticks cputime accounting can be tested on the given arch. Signed-off-by: Frederic Weisbecker Cc: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Zijlstra Cc: Borislav Petkov Cc: Li Zhong Cc: Mike Galbraith Cc: Kevin Hilman

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

2013-05-15T21:05:17Z

Pull timer fixes from Thomas Gleixner: - Cure for not using zalloc in the first place, which leads to random crashes with CPUMASK_OFF_STACK. - Revert a user space visible change which broke udev - Add a missing cpu_online early return introduced by the new full dyntick conversions - Plug a long standing race in the timer wheel cpu hotplug code. Sigh... - Cleanup NOHZ per cpu data on cpu down to prevent stale data on cpu up. * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: time: Revert ALWAYS_USE_PERSISTENT_CLOCK compile time optimizaitons timer: Don't reinitialize the cpu base lock during CPU_UP_PREPARE tick: Don't invoke tick_nohz_stop_sched_tick() if the cpu is offline tick: Cleanup NOHZ per cpu data on cpu down tick: Use zalloc_cpumask_var for allocating offstack cpumasks

time: Revert ALWAYS_USE_PERSISTENT_CLOCK compile time optimizaitons

2013-05-14T18:54:06Z

Kay Sievers noted that the ALWAYS_USE_PERSISTENT_CLOCK config, which enables some minor compile time optimization to avoid uncessary code in mostly the suspend/resume path could cause problems for userland. In particular, the dependency for RTC_HCTOSYS on !ALWAYS_USE_PERSISTENT_CLOCK, which avoids setting the time twice and simplifies suspend/resume, has the side effect of causing the /sys/class/rtc/rtcN/hctosys flag to always be zero, and this flag is commonly used by udev to setup the /dev/rtc symlink to /dev/rtcN, which can cause pain for older applications. While the udev rules could use some work to be less fragile, breaking userland should strongly be avoided. Additionally the compile time optimizations are fairly minor, and the code being optimized is likely to be reworked in the future, so lets revert this change. Reported-by: Kay Sievers Signed-off-by: John Stultz Cc: stable #3.9 Cc: Feng Tang Cc: Jason Gunthorpe Link: http://lkml.kernel.org/r/1366828376-18124-1-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner

rcu: Fix full dynticks' dependency on wide RCU nocb mode

2013-05-04T06:30:34Z

Commit 0637e029392386e6996f5d6574aadccee8315efa ("nohz: Select wide RCU nocb for full dynticks") intended to force CONFIG_RCU_NOCB_CPU_ALL=y when full dynticks is enabled. However this option is part of a choice menu and Kconfig's "select" instruction has no effect on such targets. Fix this by using reverse dependencies on the targets we don't want instead. Reviewed-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker Cc: Christoph Lameter Cc: Hakan Akkan Cc: Ingo Molnar Cc: Kevin Hilman Cc: Li Zhong Cc: Paul Gortmaker Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner

nohz: Select VIRT_CPU_ACCOUNTING_GEN from full dynticks config

2013-04-26T16:56:59Z

Turn the full dynticks passive dependency on VIRT_CPU_ACCOUNTING_GEN to an active one. The full dynticks Kconfig is currently hidden behind the full dynticks cputime accounting, which is an awkward and counter-intuitive layout: the user first has to select the dynticks cputime accounting in order to make the full dynticks feature to be visible. We definetly want it the other way around. The usual way to perform this kind of active dependency is use "select" on the depended target. Now we can't use the Kconfig "select" instruction when the target is a "choice". So this patch inspires on how the RCU subsystem Kconfig interact with its dependencies on SMP and PREEMPT: we make sure that cputime accounting can't propose another option than VIRT_CPU_ACCOUNTING_GEN when NO_HZ_FULL is selected by using the right "depends on" instruction for each cputime accounting choices. v2: Keep full dynticks cputime accounting available even without full dynticks, as per Paul McKenney's suggestion. Reported-by: Ingo Molnar Signed-off-by: Frederic Weisbecker Cc: Christoph Lameter Cc: Hakan Akkan Cc: Ingo Molnar Cc: Kevin Hilman Cc: Li Zhong Cc: Paul E. McKenney Cc: Paul Gortmaker Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner