pm24.git/kernel/time, branch v5.4-rc4

hrtimer: Annotate lockless access to timer->base

2019-10-14T13:51:49Z

Followup to commit dd2261ed45aa ("hrtimer: Protect lockless access to timer->base") lock_hrtimer_base() fetches timer->base without lock exclusion. Compiler is allowed to read timer->base twice (even if considered dumb) which could end up trying to lock migration_base and return &migration_base. base = timer->base; if (likely(base != &migration_base)) { /* compiler reads timer->base again, and now (base == &migration_base) raw_spin_lock_irqsave(&base->cpu_base->lock, *flags); if (likely(base == timer->base)) return base; /* == &migration_base ! */ Similarly the write sides must use WRITE_ONCE() to avoid store tearing. Signed-off-by: Eric Dumazet Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20191008173204.180879-1-edumazet@google.com

tick: broadcast-hrtimer: Fix a race in bc_set_next

2019-09-27T12:45:55Z

When a cpu requests broadcasting, before starting the tick broadcast hrtimer, bc_set_next() checks if the timer callback (bc_handler) is active using hrtimer_try_to_cancel(). But hrtimer_try_to_cancel() does not provide the required synchronization when the callback is active on other core. The callback could have already executed tick_handle_oneshot_broadcast() and could have also returned. But still there is a small time window where the hrtimer_try_to_cancel() returns -1. In that case bc_set_next() returns without doing anything, but the next_event of the tick broadcast clock device is already set to a timeout value. In the race condition diagram below, CPU #1 is running the timer callback and CPU #2 is entering idle state and so calls bc_set_next(). In the worst case, the next_event will contain an expiry time, but the hrtimer will not be started which happens when the racing callback returns HRTIMER_NORESTART. The hrtimer might never recover if all further requests from the CPUs to subscribe to tick broadcast have timeout greater than the next_event of tick broadcast clock device. This leads to cascading of failures and finally noticed as rcu stall warnings Here is a depiction of the race condition CPU #1 (Running timer callback) CPU #2 (Enter idle and subscribe to tick broadcast) --------------------- --------------------- __run_hrtimer() tick_broadcast_enter() bc_handler() __tick_broadcast_oneshot_control() tick_handle_oneshot_broadcast() raw_spin_lock(&tick_broadcast_lock); dev->next_event = KTIME_MAX; //wait for tick_broadcast_lock //next_event for tick broadcast clock set to KTIME_MAX since no other cores subscribed to tick broadcasting raw_spin_unlock(&tick_broadcast_lock); if (dev->next_event == KTIME_MAX) return HRTIMER_NORESTART // callback function exits without restarting the hrtimer //tick_broadcast_lock acquired raw_spin_lock(&tick_broadcast_lock); tick_broadcast_set_event() clockevents_program_event() dev->next_event = expires; bc_set_next() hrtimer_try_to_cancel() //returns -1 since the timer callback is active. Exits without restarting the timer cpu_base->running = NULL; The comment that hrtimer cannot be armed from within the callback is wrong. It is fine to start the hrtimer from within the callback. Also it is safe to start the hrtimer from the enter/exit idle code while the broadcast handler is active. The enter/exit idle code and the broadcast handler are synchronized using tick_broadcast_lock. So there is no need for the existing try to cancel logic. All this can be removed which will eliminate the race condition as well. Fixes: 5d1638acb9f6 ("tick: Introduce hrtimer based broadcast") Originally-by: Thomas Gleixner Signed-off-by: Balasubramani Vivekanandan Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190926135101.12102-2-balasubramani_vivekanandan@mentor.com

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

2019-09-26T22:53:17Z

Pull timer fix from Ingo Molnar: "Fix a timer expiry bug that would cause spurious delay of timers" * 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: timer: Read jiffies once when forwarding base clk

timer: Read jiffies once when forwarding base clk

2019-09-19T15:50:11Z

The timer delayed for more than 3 seconds warning was triggered during testing. Workqueue: events_unbound sched_tick_remote RIP: 0010:sched_tick_remote+0xee/0x100 ... Call Trace: process_one_work+0x18c/0x3a0 worker_thread+0x30/0x380 kthread+0x113/0x130 ret_from_fork+0x22/0x40 The reason is that the code in collect_expired_timers() uses jiffies unprotected: if (next_event > jiffies) base->clk = jiffies; As the compiler is allowed to reload the value base->clk can advance between the check and the store and in the worst case advance farther than next event. That causes the timer expiry to be delayed until the wheel pointer wraps around. Convert the code to use READ_ONCE() Fixes: 236968383cf5 ("timers: Optimize collect_expired_timers() for NOHZ") Signed-off-by: Li RongQing Signed-off-by: Liang ZhiCheng Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/1568894687-14499-1-git-send-email-lirongqing@baidu.com

Merge tag 'pm-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

2019-09-18T02:15:14Z

Pull power management updates from Rafael Wysocki: "These include a rework of the main suspend-to-idle code flow (related to the handling of spurious wakeups), a switch over of several users of cpufreq notifiers to QoS-based limits, a new devfreq driver for Tegra20, a new cpuidle driver and governor for virtualized guests, an extension of the wakeup sources framework to expose wakeup sources as device objects in sysfs, and more. Specifics: - Rework the main suspend-to-idle control flow to avoid repeating "noirq" device resume and suspend operations in case of spurious wakeups from the ACPI EC and decouple the ACPI EC wakeups support from the LPS0 _DSM support (Rafael Wysocki). - Extend the wakeup sources framework to expose wakeup sources as device objects in sysfs (Tri Vo, Stephen Boyd). - Expose system suspend statistics in sysfs (Kalesh Singh). - Introduce a new haltpoll cpuidle driver and a new matching governor for virtualized guests wanting to do guest-side polling in the idle loop (Marcelo Tosatti, Joao Martins, Wanpeng Li, Stephen Rothwell). - Fix the menu and teo cpuidle governors to allow the scheduler tick to be stopped if PM QoS is used to limit the CPU idle state exit latency in some cases (Rafael Wysocki). - Increase the resolution of the play_idle() argument to microseconds for more fine-grained injection of CPU idle cycles (Daniel Lezcano). - Switch over some users of cpuidle notifiers to the new QoS-based frequency limits and drop the CPUFREQ_ADJUST and CPUFREQ_NOTIFY policy notifier events (Viresh Kumar). - Add new cpufreq driver based on nvmem for sun50i (Yangtao Li). - Add support for MT8183 and MT8516 to the mediatek cpufreq driver (Andrew-sh.Cheng, Fabien Parent). - Add i.MX8MN support to the imx-cpufreq-dt cpufreq driver (Anson Huang). - Add qcs404 to cpufreq-dt-platdev blacklist (Jorge Ramirez-Ortiz). - Update the qcom cpufreq driver (among other things, to make it easier to extend and to use kryo cpufreq for other nvmem-based SoCs) and add qcs404 support to it (Niklas Cassel, Douglas RAILLARD, Sibi Sankar, Sricharan R). - Fix assorted issues and make assorted minor improvements in the cpufreq code (Colin Ian King, Douglas RAILLARD, Florian Fainelli, Gustavo Silva, Hariprasad Kelam). - Add new devfreq driver for NVidia Tegra20 (Dmitry Osipenko, Arnd Bergmann). - Add new Exynos PPMU events to devfreq events and extend that mechanism (Lukasz Luba). - Fix and clean up the exynos-bus devfreq driver (Kamil Konieczny). - Improve devfreq documentation and governor code, fix spelling typos in devfreq (Ezequiel Garcia, Krzysztof Kozlowski, Leonard Crestez, MyungJoo Ham, Gaël PORTAY). - Add regulators enable and disable to the OPP (operating performance points) framework (Kamil Konieczny). - Update the OPP framework to support multiple opp-suspend properties (Anson Huang). - Fix assorted issues and make assorted minor improvements in the OPP code (Niklas Cassel, Viresh Kumar, Yue Hu). - Clean up the generic power domains (genpd) framework (Ulf Hansson). - Clean up assorted pieces of power management code and documentation (Akinobu Mita, Amit Kucheria, Chuhong Yuan). - Update the pm-graph tool to version 5.5 including multiple fixes and improvements (Todd Brandt). - Update the cpupower utility (Benjamin Weis, Geert Uytterhoeven, Sébastien Szymanski)" * tag 'pm-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (126 commits) cpuidle-haltpoll: Enable kvm guest polling when dedicated physical CPUs are available cpuidle-haltpoll: do not set an owner to allow modunload cpuidle-haltpoll: return -ENODEV on modinit failure cpuidle-haltpoll: set haltpoll as preferred governor cpuidle: allow governor switch on cpuidle_register_driver() PM: runtime: Documentation: add runtime_status ABI document pm-graph: make setVal unbuffered again for python2 and python3 powercap: idle_inject: Use higher resolution for idle injection cpuidle: play_idle: Increase the resolution to usec cpuidle-haltpoll: vcpu hotplug support cpufreq: Add qcs404 to cpufreq-dt-platdev blacklist cpufreq: qcom: Add support for qcs404 on nvmem driver cpufreq: qcom: Refactor the driver to make it easier to extend cpufreq: qcom: Re-organise kryo cpufreq to use it for other nvmem based qcom socs dt-bindings: opp: Add qcom-opp bindings with properties needed for CPR dt-bindings: opp: qcom-nvmem: Support pstates provided by a power domain Documentation: cpufreq: Update policy notifier documentation cpufreq: Remove CPUFREQ_ADJUST and CPUFREQ_NOTIFY policy notifier events PM / Domains: Verify PM domain type in dev_pm_genpd_set_performance_state() PM / Domains: Simplify genpd_lookup_dev() ...

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

2019-09-17T19:35:15Z

Pull core timer updates from Thomas Gleixner: "Timers and timekeeping updates: - A large overhaul of the posix CPU timer code which is a preparation for moving the CPU timer expiry out into task work so it can be properly accounted on the task/process. An update to the bogus permission checks will come later during the merge window as feedback was not complete before heading of for travel. - Switch the timerqueue code to use cached rbtrees and get rid of the homebrewn caching of the leftmost node. - Consolidate hrtimer_init() + hrtimer_init_sleeper() calls into a single function - Implement the separation of hrtimers to be forced to expire in hard interrupt context even when PREEMPT_RT is enabled and mark the affected timers accordingly. - Implement a mechanism for hrtimers and the timer wheel to protect RT against priority inversion and live lock issues when a (hr)timer which should be canceled is currently executing the callback. Instead of infinitely spinning, the task which tries to cancel the timer blocks on a per cpu base expiry lock which is held and released by the (hr)timer expiry code. - Enable the Hyper-V TSC page based sched_clock for Hyper-V guests resulting in faster access to timekeeping functions. - Updates to various clocksource/clockevent drivers and their device tree bindings. - The usual small improvements all over the place" * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (101 commits) posix-cpu-timers: Fix permission check regression posix-cpu-timers: Always clear head pointer on dequeue hrtimer: Add a missing bracket and hide `migration_base' on !SMP posix-cpu-timers: Make expiry_active check actually work correctly posix-timers: Unbreak CONFIG_POSIX_TIMERS=n build tick: Mark sched_timer to expire in hard interrupt context hrtimer: Add kernel doc annotation for HRTIMER_MODE_HARD x86/hyperv: Hide pv_ops access for CONFIG_PARAVIRT=n posix-cpu-timers: Utilize timerqueue for storage posix-cpu-timers: Move state tracking to struct posix_cputimers posix-cpu-timers: Deduplicate rlimit handling posix-cpu-timers: Remove pointless comparisons posix-cpu-timers: Get rid of 64bit divisions posix-cpu-timers: Consolidate timer expiry further posix-cpu-timers: Get rid of zero checks rlimit: Rewrite non-sensical RLIMIT_CPU comment posix-cpu-timers: Respect INFINITY for hard RTTIME limit posix-cpu-timers: Switch thread group sampling to array posix-cpu-timers: Restructure expiry array posix-cpu-timers: Remove cputime_expires ...

Merge branch 'pm-sleep'

2019-09-17T07:36:34Z

* pm-sleep: (29 commits) ACPI: PM: s2idle: Always set up EC GPE for system wakeup ACPI: PM: s2idle: Avoid rearming SCI for wakeup unnecessarily PM / wakeup: Unexport wakeup_source_sysfs_{add,remove}() PM / wakeup: Register wakeup class kobj after device is added PM / wakeup: Fix sysfs registration error path PM / wakeup: Show wakeup sources stats in sysfs PM / wakeup: Use wakeup_source_register() in wakelock.c PM / wakeup: Drop wakeup_source_init(), wakeup_source_prepare() PM: sleep: Replace strncmp() with str_has_prefix() PM: suspend: Fix platform_suspend_prepare_noirq() intel-hid: Disable button array during suspend-to-idle intel-hid: intel-vbtn: Avoid leaking wakeup_mode set ACPI: PM: s2idle: Execute LPS0 _DSM functions with suspended devices ACPI: EC: PM: Make acpi_ec_dispatch_gpe() print debug message ACPI: EC: PM: Consolidate some code depending on PM_SLEEP ACPI: PM: s2idle: Eliminate acpi_sleep_no_ec_events() ACPI: PM: s2idle: Switch EC over to polling during "noirq" suspend ACPI: PM: s2idle: Add acpi.sleep_no_lps0 module parameter ACPI: PM: s2idle: Rearrange lps0_device_attach() PM/sleep: Expose suspend stats in sysfs ...

posix-cpu-timers: Fix permission check regression

2019-09-10T11:13:07Z

The recent consolidation of the three permission checks introduced a subtle regression. For timer_create() with a process wide timer it returns the current task if the lookup through the PID which is encoded into the clockid results in returning current. That's broken because it does not validate whether the current task is the group leader. That was caused by the two different variants of permission checks: - posix_cpu_timer_get() allowed access to the process wide clock when the looked up task is current. That's not an issue because the process wide clock is in the shared sighand. - posix_cpu_timer_create() made sure that the looked up task is the group leader. Restore the previous state. Note, that these permission checks are more than questionable, but that's subject to follow up changes. Fixes: 6ae40e3fdcd3 ("posix-cpu-timers: Provide task validation functions") Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1909052314110.1902@nanos.tec.linutronix.de

alarmtimer: Use EOPNOTSUPP instead of ENOTSUPP

2019-09-05T19:19:26Z

ENOTSUPP is not supposed to be returned to userspace. This was found on an OpenPower machine, where the RTC does not support set_alarm. On that system, a clock_nanosleep(CLOCK_REALTIME_ALARM, ...) results in "524 Unknown error 524" Replace it with EOPNOTSUPP which results in the expected "95 Operation not supported" error. Fixes: 1c6b39ad3f01 (alarmtimers: Return -ENOTSUPP if no RTC device is present) Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20190903171802.28314-1-cascardo@canonical.com

hrtimer: Add a missing bracket and hide `migration_base' on !SMP

2019-09-05T08:39:06Z

The recent change to avoid taking the expiry lock when a timer is currently migrated missed to add a bracket at the end of the if statement leading to compile errors. Since that commit the variable `migration_base' is always used but it is only available on SMP configuration thus leading to another compile error. The changelog says "The timer base and base->cpu_base cannot be NULL in the code path", so it is safe to limit this check to SMP configurations only. Add the missing bracket to the if statement and hide `migration_base' behind CONFIG_SMP bars. [ tglx: Mark the functions inline ... ] Fixes: 68b2c8c1e4210 ("hrtimer: Don't take expiry_lock when timer is currently migrated") Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20190904145527.eah7z56ntwobqm6j@linutronix.de