user/sven/linux.git/kernel/time, branch v5.12.18

clocksource: Check per-CPU clock synchronization when marked unstable

2021-07-14T14:59:28Z

[ Upstream commit 7560c02bdffb7c52d1457fa551b9e745d4b9e754 ] Some sorts of per-CPU clock sources have a history of going out of synchronization with each other. However, this problem has purportedy been solved in the past ten years. Except that it is all too possible that the problem has instead simply been made less likely, which might mean that some of the occasional "Marking clocksource 'tsc' as unstable" messages might be due to desynchronization. How would anyone know? Therefore apply CPU-to-CPU synchronization checking to newly unstable clocksource that are marked with the new CLOCK_SOURCE_VERIFY_PERCPU flag. Lists of desynchronized CPUs are printed, with the caveat that if it is the reporting CPU that is itself desynchronized, it will appear that all the other clocks are wrong. Just like in real life. Reported-by: Chris Mason Signed-off-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Acked-by: Feng Tang Link: https://lore.kernel.org/r/20210527190124.440372-2-paulmck@kernel.org Signed-off-by: Sasha Levin

clocksource: Retry clock read if long delays detected

2021-07-14T14:59:28Z

[ Upstream commit db3a34e17433de2390eb80d436970edcebd0ca3e ] When the clocksource watchdog marks a clock as unstable, this might be due to that clock being unstable or it might be due to delays that happen to occur between the reads of the two clocks. Yes, interrupts are disabled across those two reads, but there are no shortage of things that can delay interrupts-disabled regions of code ranging from SMI handlers to vCPU preemption. It would be good to have some indication as to why the clock was marked unstable. Therefore, re-read the watchdog clock on either side of the read from the clock under test. If the watchdog clock shows an excessive time delta between its pair of reads, the reads are retried. The maximum number of retries is specified by a new kernel boot parameter clocksource.max_cswd_read_retries, which defaults to three, that is, up to four reads, one initial and up to three retries. If more than one retry was required, a message is printed on the console (the occasional single retry is expected behavior, especially in guest OSes). If the maximum number of retries is exceeded, the clock under test will be marked unstable. However, the probability of this happening due to various sorts of delays is quite small. In addition, the reason (clock-read delays) for the unstable marking will be apparent. Reported-by: Chris Mason Signed-off-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Acked-by: Feng Tang Link: https://lore.kernel.org/r/20210527190124.440372-1-paulmck@kernel.org Signed-off-by: Sasha Levin

tick/nohz: Only check for RCU deferred wakeup on user/guest entry when needed

2021-06-16T10:05:06Z

commit f268c3737ecaefcfeecfb4cb5e44958a8976f067 upstream. Checking for and processing RCU-nocb deferred wakeup upon user/guest entry is only relevant when nohz_full runs on the local CPU, otherwise the periodic tick should take care of it. Make sure we don't needlessly pollute these fast-paths as a -3% performance regression on a will-it-scale.per_process_ops has been reported so far. Fixes: 47b8ff194c1f (entry: Explicitly flush pending rcuog wakeup before last rescheduling point) Fixes: 4ae7dc97f726 (entry/kvm: Explicitly flush pending rcuog wakeup before last rescheduling point) Reported-by: kernel test robot Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Paul E. McKenney Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20210527113441.465489-1-frederic@kernel.org Signed-off-by: Greg Kroah-Hartman

alarmtimer: Check RTC features instead of ops

2021-05-19T08:56:41Z

commit e09784a8a751e539dffc94d43bc917b0ac1e934a upstream. RTC drivers used to leave .set_alarm() NULL in order to signal the RTC device doesn't support alarms. The drivers are now clearing the RTC_FEATURE_ALARM bit for that purpose in order to keep the rtc_class_ops structure const. So now, .set_alarm() is set unconditionally and this possibly causes the alarmtimer code to select an RTC device that doesn't support alarms. Test RTC_FEATURE_ALARM instead of relying on ops->set_alarm to determine whether alarms are available. Fixes: 7ae41220ef58 ("rtc: introduce features bitfield") Signed-off-by: Alexandre Belloni Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210511014516.563031-1-alexandre.belloni@bootlin.com Signed-off-by: Greg Kroah-Hartman

posix-timers: Preserve return value in clock_adjtime32()

2021-05-12T06:39:33Z

commit 2d036dfa5f10df9782f5278fc591d79d283c1fad upstream. The return value on success (>= 0) is overwritten by the return value of put_old_timex32(). That works correct in the fault case, but is wrong for the success case where put_old_timex32() returns 0. Just check the return value of put_old_timex32() and return -EFAULT in case it is not zero. [ tglx: Massage changelog ] Fixes: 3a4d44b61625 ("ntp: Move adjtimex related compat syscalls to native counterparts") Signed-off-by: Chen Jun Signed-off-by: Thomas Gleixner Reviewed-by: Richard Cochran Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210414030449.90692-1-chenjun102@huawei.com Signed-off-by: Greg Kroah-Hartman

kernel, fs: Introduce and use set_restart_fn() and arch_set_restart_data()

2021-03-16T21:13:10Z

Preparation for fixing get_nr_restart_syscall() on X86 for COMPAT. Add a new helper which sets restart_block->fn and calls a dummy arch_set_restart_data() helper. Fixes: 609c19a385c8 ("x86/ptrace: Stop setting TS_COMPAT in ptrace code") Signed-off-by: Oleg Nesterov Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210201174641.GA17871@redhat.com

hrtimer: Update softirq_expires_next correctly after __hrtimer_get_next_event()

2021-03-08T08:37:01Z

hrtimer_force_reprogram() and hrtimer_interrupt() invokes __hrtimer_get_next_event() to find the earliest expiry time of hrtimer bases. __hrtimer_get_next_event() does not update cpu_base::[softirq_]_expires_next to preserve reprogramming logic. That needs to be done at the callsites. hrtimer_force_reprogram() updates cpu_base::softirq_expires_next only when the first expiring timer is a softirq timer and the soft interrupt is not activated. That's wrong because cpu_base::softirq_expires_next is left stale when the first expiring timer of all bases is a timer which expires in hard interrupt context. hrtimer_interrupt() does never update cpu_base::softirq_expires_next which is wrong too. That becomes a problem when clock_settime() sets CLOCK_REALTIME forward and the first soft expiring timer is in the CLOCK_REALTIME_SOFT base. Setting CLOCK_REALTIME forward moves the clock MONOTONIC based expiry time of that timer before the stale cpu_base::softirq_expires_next. cpu_base::softirq_expires_next is cached to make the check for raising the soft interrupt fast. In the above case the soft interrupt won't be raised until clock monotonic reaches the stale cpu_base::softirq_expires_next value. That's incorrect, but what's worse it that if the softirq timer becomes the first expiring timer of all clock bases after the hard expiry timer has been handled the reprogramming of the clockevent from hrtimer_interrupt() will result in an interrupt storm. That happens because the reprogramming does not use cpu_base::softirq_expires_next, it uses __hrtimer_get_next_event() which returns the actual expiry time. Once clock MONOTONIC reaches cpu_base::softirq_expires_next the soft interrupt is raised and the storm subsides. Change the logic in hrtimer_force_reprogram() to evaluate the soft and hard bases seperately, update softirq_expires_next and handle the case when a soft expiring timer is the first of all bases by comparing the expiry times and updating the required cpu base fields. Split this functionality into a separate function to be able to use it in hrtimer_interrupt() as well without copy paste. Fixes: 5da70160462e ("hrtimer: Implement support for softirq based hrtimers") Reported-by: Mikael Beckius Suggested-by: Thomas Gleixner Tested-by: Mikael Beckius Signed-off-by: Anna-Maria Behnsen Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20210223160240.27518-1-anna-maria@linutronix.de

Merge tag 'core-rcu-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2021-02-21T20:04:41Z

Pull RCU updates from Ingo Molnar: "These are the latest RCU updates for v5.12: - Documentation updates. - Miscellaneous fixes. - kfree_rcu() updates: Addition of mem_dump_obj() to provide allocator return addresses to more easily locate bugs. This has a couple of RCU-related commits, but is mostly MM. Was pulled in with akpm's agreement. - Per-callback-batch tracking of numbers of callbacks, which enables better debugging information and smarter reactions to large numbers of callbacks. - The first round of changes to allow CPUs to be runtime switched from and to callback-offloaded state. - CONFIG_PREEMPT_RT-related changes. - RCU CPU stall warning updates. - Addition of polling grace-period APIs for SRCU. - Torture-test and torture-test scripting updates, including a "torture everything" script that runs rcutorture, locktorture, scftorture, rcuscale, and refscale. Plus does an allmodconfig build. - nolibc fixes for the torture tests" * tag 'core-rcu-2021-02-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (130 commits) percpu_ref: Dump mem_dump_obj() info upon reference-count underflow rcu: Make call_rcu() print mem_dump_obj() info for double-freed callback mm: Make mem_obj_dump() vmalloc() dumps include start and length mm: Make mem_dump_obj() handle vmalloc() memory mm: Make mem_dump_obj() handle NULL and zero-sized pointers mm: Add mem_dump_obj() to print source of memory block tools/rcutorture: Fix position of -lgcc in mkinitrd.sh tools/nolibc: Fix position of -lgcc in the documented example tools/nolibc: Emit detailed error for missing alternate syscall number definitions tools/nolibc: Remove incorrect definitions of __ARCH_WANT_* tools/nolibc: Get timeval, timespec and timezone from linux/time.h tools/nolibc: Implement poll() based on ppoll() tools/nolibc: Implement fork() based on clone() tools/nolibc: Make getpgrp() fall back to getpgid(0) tools/nolibc: Make dup2() rely on dup3() when available tools/nolibc: Add the definition for dup() rcutorture: Add rcutree.use_softirq=0 to RUDE01 and TASKS01 torture: Maintain torture-specific set of CPUs-online books torture: Clean up after torture-test CPU hotplugging rcutorture: Make object_debug also double call_rcu() heap object ...

Merge tag 'timers-core-2021-02-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2021-02-21T19:55:43Z

Pull timer updates from Thomas Gleixner: "Time and timer updates: - Instead of new drivers remove tango, sirf, u300 and atlas drivers - Add suspend/resume support for microchip pit64b - The usual fixes, improvements and cleanups here and there" * tag 'timers-core-2021-02-15' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: timens: Delete no-op time_ns_init() alarmtimer: Update kerneldoc clocksource/drivers/timer-microchip-pit64b: Add clocksource suspend/resume clocksource/drivers/prima: Remove sirf prima driver clocksource/drivers/atlas: Remove sirf atlas driver clocksource/drivers/tango: Remove tango driver clocksource/drivers/u300: Remove the u300 driver dt-bindings: timer: nuvoton: Clarify that interrupt of timer 0 should be specified clocksource/drivers/davinci: Move pr_fmt() before the includes clocksource/drivers/efm32: Drop unused timer code

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

2021-02-12T11:56:55Z

Pull RCU updates from Paul E. McKenney: - Documentation updates. - Miscellaneous fixes. - kfree_rcu() updates: Addition of mem_dump_obj() to provide allocator return addresses to more easily locate bugs. This has a couple of RCU-related commits, but is mostly MM. Was pulled in with akpm's agreement. - Per-callback-batch tracking of numbers of callbacks, which enables better debugging information and smarter reactions to large numbers of callbacks. - The first round of changes to allow CPUs to be runtime switched from and to callback-offloaded state. - CONFIG_PREEMPT_RT-related changes. - RCU CPU stall warning updates. - Addition of polling grace-period APIs for SRCU. - Torture-test and torture-test scripting updates, including a "torture everything" script that runs rcutorture, locktorture, scftorture, rcuscale, and refscale. Plus does an allmodconfig build. Signed-off-by: Ingo Molnar