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* Merge branch 'timers-core-for-linus' of ↵Linus Torvalds2017-11-132-6/+7
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull timer updates from Thomas Gleixner: "Yet another big pile of changes: - More year 2038 work from Arnd slowly reaching the point where we need to think about the syscalls themself. - A new timer function which allows to conditionally (re)arm a timer only when it's either not running or the new expiry time is sooner than the armed expiry time. This allows to use a single timer for multiple timeout requirements w/o caring about the first expiry time at the call site. - A new NMI safe accessor to clock real time for the printk timestamp work. Can be used by tracing, perf as well if required. - A large number of timer setup conversions from Kees which got collected here because either maintainers requested so or they simply got ignored. As Kees pointed out already there are a few trivial merge conflicts and some redundant commits which was unavoidable due to the size of this conversion effort. - Avoid a redundant iteration in the timer wheel softirq processing. - Provide a mechanism to treat RTC implementations depending on their hardware properties, i.e. don't inflict the write at the 0.5 seconds boundary which originates from the PC CMOS RTC to all RTCs. No functional change as drivers need to be updated separately. - The usual small updates to core code clocksource drivers. Nothing really exciting" * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (111 commits) timers: Add a function to start/reduce a timer pstore: Use ktime_get_real_fast_ns() instead of __getnstimeofday() timer: Prepare to change all DEFINE_TIMER() callbacks netfilter: ipvs: Convert timers to use timer_setup() scsi: qla2xxx: Convert timers to use timer_setup() block/aoe: discover_timer: Convert timers to use timer_setup() ide: Convert timers to use timer_setup() drbd: Convert timers to use timer_setup() mailbox: Convert timers to use timer_setup() crypto: Convert timers to use timer_setup() drivers/pcmcia: omap1: Fix error in automated timer conversion ARM: footbridge: Fix typo in timer conversion drivers/sgi-xp: Convert timers to use timer_setup() drivers/pcmcia: Convert timers to use timer_setup() drivers/memstick: Convert timers to use timer_setup() drivers/macintosh: Convert timers to use timer_setup() hwrng/xgene-rng: Convert timers to use timer_setup() auxdisplay: Convert timers to use timer_setup() sparc/led: Convert timers to use timer_setup() mips: ip22/32: Convert timers to use timer_setup() ...
| * rcu: Convert timers to use timer_setup()Kees Cook2017-11-022-6/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | In preparation for unconditionally passing the struct timer_list pointer to all timer callbacks, switch to using the new timer_setup() and from_timer() to pass the timer pointer explicitly. Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Signed-off-by: Kees Cook <keescook@chromium.org>
* | Merge branch 'sched-core-for-linus' of ↵Linus Torvalds2017-11-132-2/+4
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler updates from Ingo Molnar: "The main updates in this cycle were: - Group balancing enhancements and cleanups (Brendan Jackman) - Move CPU isolation related functionality into its separate kernel/sched/isolation.c file, with related 'housekeeping_*()' namespace and nomenclature et al. (Frederic Weisbecker) - Improve the interactive/cpu-intense fairness calculation (Josef Bacik) - Improve the PELT code and related cleanups (Peter Zijlstra) - Improve the logic of pick_next_task_fair() (Uladzislau Rezki) - Improve the RT IPI based balancing logic (Steven Rostedt) - Various micro-optimizations: - better !CONFIG_SCHED_DEBUG optimizations (Patrick Bellasi) - better idle loop (Cheng Jian) - ... plus misc fixes, cleanups and updates" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits) sched/core: Optimize sched_feat() for !CONFIG_SCHED_DEBUG builds sched/sysctl: Fix attributes of some extern declarations sched/isolation: Document isolcpus= boot parameter flags, mark it deprecated sched/isolation: Add basic isolcpus flags sched/isolation: Move isolcpus= handling to the housekeeping code sched/isolation: Handle the nohz_full= parameter sched/isolation: Introduce housekeeping flags sched/isolation: Split out new CONFIG_CPU_ISOLATION=y config from CONFIG_NO_HZ_FULL sched/isolation: Rename is_housekeeping_cpu() to housekeeping_cpu() sched/isolation: Use its own static key sched/isolation: Make the housekeeping cpumask private sched/isolation: Provide a dynamic off-case to housekeeping_any_cpu() sched/isolation, watchdog: Use housekeeping_cpumask() instead of ad-hoc version sched/isolation: Move housekeeping related code to its own file sched/idle: Micro-optimize the idle loop sched/isolcpus: Fix "isolcpus=" boot parameter handling when !CONFIG_CPUMASK_OFFSTACK x86/tsc: Append the 'tsc=' description for the 'tsc=unstable' boot parameter sched/rt: Simplify the IPI based RT balancing logic block/ioprio: Use a helper to check for RT prio sched/rt: Add a helper to test for a RT task ...
| * \ Merge branch 'linus' into sched/core, to pick up fixesIngo Molnar2017-11-084-12/+18
| |\ \ | | | | | | | | | | | | Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | sched/isolation: Introduce housekeeping flagsFrederic Weisbecker2017-10-272-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Before we implement isolcpus under housekeeping, we need the isolation features to be more finegrained. For example some people want NOHZ_FULL without the full scheduler isolation, others want full scheduler isolation without NOHZ_FULL. So let's cut all these isolation features piecewise, at the risk of overcutting it right now. We can still merge some flags later if they always make sense together. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Christoph Lameter <cl@linux.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Wanpeng Li <kernellwp@gmail.com> Link: http://lkml.kernel.org/r/1509072159-31808-9-git-send-email-frederic@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * | | sched/isolation: Move housekeeping related code to its own fileFrederic Weisbecker2017-10-272-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The housekeeping code is currently tied to the NOHZ code. As we are planning to make housekeeping independent from it, start with moving the relevant code to its own file. Signed-off-by: Frederic Weisbecker <frederic@kernel.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Christoph Lameter <cl@linux.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rik van Riel <riel@redhat.com> Cc: Wanpeng Li <kernellwp@gmail.com> Link: http://lkml.kernel.org/r/1509072159-31808-2-git-send-email-frederic@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | | | Merge branch 'locking-core-for-linus' of ↵Linus Torvalds2017-11-132-13/+13
|\ \ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 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/enabledFrederic Weisbecker2017-11-082-13/+13
| | |/ / | |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <frederic@kernel.org> Acked-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: David S . Miller <davem@davemloft.net> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Tejun Heo <tj@kernel.org> Link: http://lkml.kernel.org/r/1509980490-4285-15-git-send-email-frederic@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | | | Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds2017-11-137-62/+187
|\ \ \ \ | |/ / / |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull RCU updates from Ingo Molnar: "The main changes in this cycle are: - Documentation updates - RCU CPU stall-warning updates - Torture-test updates - Miscellaneous fixes Size wise the biggest updates are to documentation. Excluding documentation most of the code increase comes from a single commit which expands debugging" * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits) srcu: Add parameters to SRCU docbook comments doc: Rewrite confusing statement about memory barriers memory-barriers.txt: Fix typo in pairing example rcu/segcblist: Include rcupdate.h rcu: Add extended-quiescent-state testing advice rcu: Suppress lockdep false-positive ->boost_mtx complaints rcu: Do not include rtmutex_common.h unconditionally torture: Provide TMPDIR environment variable to specify tmpdir rcutorture: Dump writer stack if stalled rcutorture: Add interrupt-disable capability to stall-warning tests rcu: Suppress RCU CPU stall warnings while dumping trace rcu: Turn off tracing before dumping trace rcu: Make RCU CPU stall warnings check for irq-disabled CPUs sched,rcu: Make cond_resched() provide RCU quiescent state sched: Make resched_cpu() unconditional irq_work: Map irq_work_on_queue() to irq_work_on() in !SMP rcu: Create call_rcu_tasks() kthread at boot time rcu: Fix up pending cbs check in rcu_prepare_for_idle memory-barriers: Rework multicopy-atomicity section memory-barriers: Replace uses of "transitive" ...
| * | | Merge branch 'for-mingo' of ↵Ingo Molnar2017-10-247-62/+187
| |\ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu Pull RCU updates from Paul E. McKenney: - Documentation updates - Miscellaneous fixes - RCU CPU stall-warning updates - Torture-test updates Signed-off-by: Ingo Molnar <mingo@kernel.org>
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| | *---. \ \ Merge branches 'doc.2017.10.20a', 'fixes.2017.10.19a', 'stall.2017.10.09a' ↵Paul E. McKenney2017-10-207-62/+187
| | |\ \ \ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | and 'torture.2017.10.09a' into HEAD 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.
| | | | | * | | rcutorture: Dump writer stack if stalledPaul E. McKenney2017-10-091-0/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Right now, rcutorture warns if an rcu_torture_writer() kthread stalls, but this warning is not always all that helpful. This commit therefore makes the first such warning include a stack dump. This in turn requires that sched_show_task() be exported to GPL modules, so this commit makes that change as well. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | | * | | rcutorture: Add interrupt-disable capability to stall-warning testsPaul E. McKenney2017-10-091-5/+13
| | | | | |/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When rcutorture sees the rcutorture.stall_cpu kernel boot parameter, it loops with preemption disabled, which does in fact normally generate an RCU CPU stall warning message. However, there are test scenarios that need the stalling CPU to have interrupts disabled. This commit therefore adds an rcutorture.stall_cpu_irqsoff kernel boot parameter that causes the stalling CPU to disable interrupts. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * | | rcu: Suppress RCU CPU stall warnings while dumping tracePaul E. McKenney2017-10-092-0/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, RCU emits Suppress RCU CPU stall warnings during its automatically initiated ftrace_dump() calls after detecting an error condition, which can result in excessively excessive console output and lost trace events. This commit therefore suppresses RCU CPU stall warnings across any of these ftrace_dump() calls. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * | | rcu: Turn off tracing before dumping tracePaul E. McKenney2017-10-091-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, RCU allows tracing to continue when it automatically does ftrace_dump() after detecting an error condition, which can result in excessively large traces and lost trace events. This commit therefore does a tracing_off() before any of these ftrace_dump() calls. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * | | rcu: Make RCU CPU stall warnings check for irq-disabled CPUsPaul E. McKenney2017-10-093-13/+103
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * | | sched,rcu: Make cond_resched() provide RCU quiescent statePaul E. McKenney2017-10-091-20/+5
| | | | |/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <mhocko@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> [ paulmck: Keep PREEMPT=n cond_resched a no-op, per Peter Zijlstra. ]
| | | * | | rcu/segcblist: Include rcupdate.hSebastian Andrzej Siewior2017-10-191-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The RT build on ARM complains about non-existing ULONG_CMP_LT. This commit therefore includes rcupdate.h into rcu_segcblist.c. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | * | | rcu: Add extended-quiescent-state testing advicePaul E. McKenney2017-10-191-0/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <paulmck@linux.vnet.ibm.com>
| | | * | | rcu: Suppress lockdep false-positive ->boost_mtx complaintsPaul E. McKenney2017-10-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | RCU priority boosting uses rt_mutex_init_proxy_locked() to initialize an rt_mutex structure in locked state held by some other task. When that other task releases it, lockdep complains (quite accurately, but a bit uselessly) that the other task never acquired it. This complaint can suppress other, more helpful, lockdep complaints, and in any case it is a false positive. This commit therefore switches from rt_mutex_unlock() to rt_mutex_futex_unlock(), thereby avoiding the lockdep annotations. Of course, if lockdep ever learns about rt_mutex_init_proxy_locked(), addtional adjustments will be required. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | * | | rcu: Do not include rtmutex_common.h unconditionallySebastian Andrzej Siewior2017-10-191-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit adjusts include files and provides definitions in preparation for suppressing lockdep false-positive ->boost_mtx complaints. Without this preparation, architectures not supporting rt_mutex will get build failures. Reported-by: kbuild test robot <fengguang.wu@intel.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | * | | rcu: Create call_rcu_tasks() kthread at boot timePaul E. McKenney2017-10-091-19/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently the call_rcu_tasks() kthread is created upon first invocation of call_rcu_tasks(). This has the advantage of avoiding creation if there are never any invocations of call_rcu_tasks() and of synchronize_rcu_tasks(), but it requires an unreliable heuristic to determine when it is safe to create the kthread. For example, it is not safe to create the kthread when call_rcu_tasks() is invoked with a spinlock held, but there is no good way to detect this in !PREEMPT kernels. This commit therefore creates this kthread unconditionally at core_initcall() time. If you don't want this kthread created, then build with CONFIG_TASKS_RCU=n. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | * | | rcu: Fix up pending cbs check in rcu_prepare_for_idleNeeraj Upadhyay2017-10-091-1/+1
| | | |/ / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The pending-callbacks check in rcu_prepare_for_idle() is backwards. It should accelerate if there are pending callbacks, but the check rather uselessly accelerates only if there are no callbacks. This commit therefore inverts this check. Fixes: 15fecf89e46a ("srcu: Abstract multi-tail callback list handling") Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: <stable@vger.kernel.org> # 4.12.x
| | * / / srcu: Add parameters to SRCU docbook commentsPaul E. McKenney2017-10-201-1/+1
| | |/ / | | | | | | | | | | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* | / / License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseGreg Kroah-Hartman2017-11-021-0/+1
|/ / / | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* / / doc: Fix various RCU docbook comment-header problemsPaul E. McKenney2017-10-193-12/+17
|/ / | | | | | | | | | | | | | | 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 <paulmck@linux.vnet.ibm.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | Merge tag 'trace-v4.14-rc1-3' of ↵Linus Torvalds2017-10-041-2/+2
|\ \ | |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace 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}()Paul E. McKenney2017-10-031-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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 <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
* | Merge tag 'trace-v4.14-rc1-2' of ↵Linus Torvalds2017-09-251-0/+10
|\| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull tracing fixes from Steven Rostedt: "Stack tracing and RCU has been having issues with each other and lockdep has been pointing out constant problems. The changes have been going into the stack tracer, but it has been discovered that the problem isn't with the stack tracer itself, but it is with calling save_stack_trace() from within the internals of RCU. The stack tracer is the one that can trigger the issue the easiest, but examining the problem further, it could also happen from a WARN() in the wrong place, or even if an NMI happened in this area and it did an rcu_read_lock(). The critical area is where RCU is not watching. Which can happen while going to and from idle, or bringing up or taking down a CPU. The final fix was to put the protection in kernel_text_address() as it is the one that requires RCU to be watching while doing the stack trace. To make this work properly, Paul had to allow rcu_irq_enter() happen after rcu_nmi_enter(). This should have been done anyway, since an NMI can page fault (reading vmalloc area), and a page fault triggers rcu_irq_enter(). One patch is just a consolidation of code so that the fix only needed to be done in one location" * tag 'trace-v4.14-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing: Remove RCU work arounds from stack tracer extable: Enable RCU if it is not watching in kernel_text_address() extable: Consolidate *kernel_text_address() functions rcu: Allow for page faults in NMI handlers
| * rcu: Allow for page faults in NMI handlersPaul E. McKenney2017-09-231-0/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A number of architecture invoke rcu_irq_enter() on exception entry in order to allow RCU read-side critical sections in the exception handler when the exception is from an idle or nohz_full CPU. This works, at least unless the exception happens in an NMI handler. In that case, rcu_nmi_enter() would already have exited the extended quiescent state, which would mean that rcu_irq_enter() would (incorrectly) cause RCU to think that it is again in an extended quiescent state. This will in turn result in lockdep splats in response to later RCU read-side critical sections. This commit therefore causes rcu_irq_enter() and rcu_irq_exit() to take no action if there is an rcu_nmi_enter() in effect, thus avoiding the unscheduled return to RCU quiescent state. This in turn should make the kernel safe for on-demand RCU voyeurism. Link: http://lkml.kernel.org/r/20170922211022.GA18084@linux.vnet.ibm.com Cc: stable@vger.kernel.org Fixes: 0be964be0 ("module: Sanitize RCU usage and locking") Reported-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
* | treewide: make "nr_cpu_ids" unsignedAlexey Dobriyan2017-09-082-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | First, number of CPUs can't be negative number. Second, different signnnedness leads to suboptimal code in the following cases: 1) kmalloc(nr_cpu_ids * sizeof(X)); "int" has to be sign extended to size_t. 2) while (loff_t *pos < nr_cpu_ids) MOVSXD is 1 byte longed than the same MOV. Other cases exist as well. Basically compiler is told that nr_cpu_ids can't be negative which can't be deduced if it is "int". Code savings on allyesconfig kernel: -3KB add/remove: 0/0 grow/shrink: 25/264 up/down: 261/-3631 (-3370) function old new delta coretemp_cpu_online 450 512 +62 rcu_init_one 1234 1272 +38 pci_device_probe 374 399 +25 ... pgdat_reclaimable_pages 628 556 -72 select_fallback_rq 446 369 -77 task_numa_find_cpu 1923 1807 -116 Link: http://lkml.kernel.org/r/20170819114959.GA30580@avx2 Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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*-----. \ Merge branches 'doc.2017.08.17a', 'fixes.2017.08.17a', ↵Paul E. McKenney2017-08-1715-586/+374
|\ \ \ \ \ | |_|_|_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 'hotplug.2017.07.25b', 'misc.2017.08.17a', 'spin_unlock_wait_no.2017.08.17a', 'srcu.2017.07.27c' and 'torture.2017.07.24c' into HEAD doc.2017.08.17a: Documentation updates. fixes.2017.08.17a: RCU fixes. hotplug.2017.07.25b: CPU-hotplug updates. misc.2017.08.17a: Miscellaneous fixes outside of RCU (give or take conflicts). spin_unlock_wait_no.2017.08.17a: Remove spin_unlock_wait(). srcu.2017.07.27c: SRCU updates. torture.2017.07.24c: Torture-test updates.
| | | | * rcutorture: Invoke call_rcu() from timer handlerPaul E. McKenney2017-07-241-0/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The Linux kernel invokes call_rcu() from various interrupt/softirq handlers, but rcutorture does not. This commit therefore adds this behavior to rcutorture's repertoire. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * rcu: Add last-CPU to GP-kthread starvation messagesPaul E. McKenney2017-07-241-2/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit augments the grace-period-kthread starvation debugging messages by adding the last CPU that ran the kthread. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * rcutorture: Eliminate unused ts_rem local from rcu_trace_clock_local()Paul E. McKenney2017-07-241-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit removes an unused local variable named ts_rem that is marked __maybe_unused. Yes, the variable was assigned to, but it was never used beyond that point, hence not needed. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * rcutorture: Add task's CPU for rcutorture writer stallsPaul E. McKenney2017-07-241-2/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It appears that at least some of the rcutorture writer stall messages coincide with unusually long CPU-online operations, for example, no fewer than 205 seconds in a recent test. It is of course possible that the writer stall is not unrelated to this unusually long CPU-hotplug operation, and so this commit adds the rcutorture writer task's CPU to the stall message to gain more information about this possible connection. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * rcutorture: Place event-traced strings into trace bufferPaul E. McKenney2017-07-241-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Strings used in event tracing need to be specially handled, for example, being copied to the trace buffer instead of being pointed to by the trace buffer. Although the TPS() macro can be used to "launder" pointed-to strings, this might not be all that effective within a loadable module. This commit therefore copies rcutorture's strings to the trace buffer. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org>
| | | | * rcutorture: Enable SRCU readers from timer handlerPaul E. McKenney2017-07-241-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now that it is legal to invoke srcu_read_lock() and srcu_read_unlock() for a given srcu_struct from both process context and {soft,}irq handlers, it is time to test it. This commit therefore enables testing of SRCU readers from rcutorture's timer handler, using in_task() to determine whether or not it is safe to sleep in the SRCU read-side critical sections. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * rcu: Remove CONFIG_TASKS_RCU ifdef from rcuperf.cPaul E. McKenney2017-07-241-16/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The synchronize_rcu_tasks() and call_rcu_tasks() APIs are now available regardless of kernel configuration, so this commit removes the CONFIG_TASKS_RCU ifdef from rcuperf.c. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * rcutorture: Print SRCU lock/unlock totalsPaul E. McKenney2017-07-241-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This commit adds printing of SRCU lock/unlock totals, which are just the sums of the per-CPU counts. Saves a bit of mental arithmetic. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | | * rcutorture: Move SRCU status printing to SRCU implementationsPaul E. McKenney2017-07-242-38/+35
| |_|_|/ |/| | | | | | | | | | | | | | | | | | | | | | | This commit gets rid of some ugly #ifdefs in rcutorture.c by moving the SRCU status printing to the SRCU implementations. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | * srcu: Provide ordering for CPU not involved in grace periodPaul E. McKenney2017-07-271-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Tree RCU guarantees that every online CPU has a memory barrier between any given grace period and any of that CPU's RCU read-side sections that must be ordered against that grace period. Since RCU doesn't always know where read-side critical sections are, the actual implementation guarantees order against prior and subsequent non-idle non-offline code, whether in an RCU read-side critical section or not. As a result, there does not need to be a memory barrier at the end of synchronize_rcu() and friends because the ordering internal to the grace period has ordered every CPU's post-grace-period execution against each CPU's pre-grace-period execution, again for all non-idle online CPUs. In contrast, SRCU can have non-idle online CPUs that are completely uninvolved in a given SRCU grace period, for example, a CPU that never runs any SRCU read-side critical sections and took no part in the grace-period processing. It is in theory possible for a given synchronize_srcu()'s wakeup to be delivered to a CPU that was completely uninvolved in the prior SRCU grace period, which could mean that the code following that synchronize_srcu() would end up being unordered with respect to both the grace period and any pre-existing SRCU read-side critical sections. This commit therefore adds an smp_mb() to the end of __synchronize_srcu(), which prevents this scenario from occurring. Reported-by: Lance Roy <ldr709@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Acked-by: Lance Roy <ldr709@gmail.com> Cc: <stable@vger.kernel.org> # 4.12.x
| | | * srcu: Make process_srcu() be staticPaul E. McKenney2017-07-241-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | The function process_srcu() is not invoked outside of srcutree.c, so this commit makes it static and drops the EXPORT_SYMBOL_GPL(). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | | * srcu: Move rcu_scheduler_starting() from Tiny RCU to Tiny SRCUPaul E. McKenney2017-07-243-49/+8
| |_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Other than lockdep support, Tiny RCU has no need for the scheduler status. However, Tiny SRCU will need this to control boot-time behavior independent of lockdep. Therefore, this commit moves rcu_scheduler_starting() from kernel/rcu/tiny_plugin.h to kernel/rcu/srcutiny.c. This in turn allows the complete removal of kernel/rcu/tiny_plugin.h. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | * rcu: Move callback-list warning to irq-disable regionPaul E. McKenney2017-07-251-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | After adopting callbacks from a newly offlined CPU, the adopting CPU checks to make sure that its callback list's count is zero only if the list has no callbacks and vice versa. Unfortunately, it does so after enabling interrupts, which means that false positives are possible due to interrupt handlers invoking call_rcu(). Although these false positives are improbable, rcutorture did make it happen once. This commit therefore moves this check to an irq-disabled region of code, thus suppressing the false positive. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | * rcu: Remove unused RCU list functionsPaul E. McKenney2017-07-252-110/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | Given changes to callback migration, rcu_cblist_head(), rcu_cblist_tail(), rcu_cblist_count_cbs(), rcu_segcblist_segempty(), rcu_segcblist_dequeued_lazy(), and rcu_segcblist_new_cbs() are no longer used. This commit therefore removes them. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | * rcu: Localize rcu_state ->orphan_pend and ->orphan_donePaul E. McKenney2017-07-254-75/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Given that the rcu_state structure's >orphan_pend and ->orphan_done fields are used only during migration of callbacks from the recently offlined CPU to a surviving CPU, if rcu_send_cbs_to_orphanage() and rcu_adopt_orphan_cbs() are combined, these fields can become local variables in the combined function. This commit therefore combines rcu_send_cbs_to_orphanage() and rcu_adopt_orphan_cbs() into a new rcu_segcblist_merge() function and removes the ->orphan_pend and ->orphan_done fields. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | * rcu: Advance callbacks after migrationPaul E. McKenney2017-07-251-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | When migrating callbacks from a newly offlined CPU, we are already holding the root rcu_node structure's lock, so it costs almost nothing to advance and accelerate the newly migrated callbacks. This patch therefore makes this advancing and acceleration happen. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | * rcu: Eliminate rcu_state ->orphan_lockPaul E. McKenney2017-07-252-15/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | The ->orphan_lock is acquired and released only within the rcu_migrate_callbacks() function, which now acquires the root rcu_node structure's ->lock. This commit therefore eliminates the ->orphan_lock in favor of the root rcu_node structure's ->lock. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| | * rcu: Advance outgoing CPU's callbacks before migrating themPaul E. McKenney2017-07-251-1/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It is possible that the outgoing CPU is unaware of recent grace periods, and so it is also possible that some of its pending callbacks are actually ready to be invoked. The current callback-migration code would needlessly force these callbacks to pass through another grace period. This commit therefore invokes rcu_advance_cbs() on the outgoing CPU's callbacks in order to give them full credit for having passed through any recent grace periods. This also fixes an odd theoretical bug where there are no callbacks in the system except for those on the outgoing CPU, none of those callbacks have yet been associated with a grace-period number, there is never again another callback registered, and the surviving CPU never again takes a scheduling-clock interrupt, never goes idle, and never enters nohz_full userspace execution. Yes, this is (just barely) possible. It requires that the surviving CPU be a nohz_full CPU, that its scheduler-clock interrupt be shut off, and that it loop forever in the kernel. You get bonus points if you can make this one happen! ;-) Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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