user/sven/linux.git/include/linux/clocksource.h, branch v5.10.154

clocksource: Reduce clocksource-skew threshold

2022-01-27T09:54:05Z

[ Upstream commit 2e27e793e280ff12cb5c202a1214c08b0d3a0f26 ] Currently, WATCHDOG_THRESHOLD is set to detect a 62.5-millisecond skew in a 500-millisecond WATCHDOG_INTERVAL. This requires that clocks be skewed by more than 12.5% in order to be marked unstable. Except that a clock that is skewed by that much is probably destroying unsuspecting software right and left. And given that there are now checks for false-positive skews due to delays between reading the two clocks, it should be possible to greatly decrease WATCHDOG_THRESHOLD, at least for fine-grained clocks such as TSC. Therefore, add a new uncertainty_margin field to the clocksource structure that contains the maximum uncertainty in nanoseconds for the corresponding clock. This field may be initialized manually, as it is for clocksource_tsc_early and clocksource_jiffies, which is copied to refined_jiffies. If the field is not initialized manually, it will be computed at clock-registry time as the period of the clock in question based on the scale and freq parameters to __clocksource_update_freq_scale() function. If either of those two parameters are zero, the tens-of-milliseconds WATCHDOG_THRESHOLD is used as a cowardly alternative to dividing by zero. No matter how the uncertainty_margin field is calculated, it is bounded below by twice WATCHDOG_MAX_SKEW, that is, by 100 microseconds. Note that manually initialized uncertainty_margin fields are not adjusted, but there is a WARN_ON_ONCE() that triggers if any such field is less than twice WATCHDOG_MAX_SKEW. This WARN_ON_ONCE() is intended to discourage production use of the one-nanosecond uncertainty_margin values that are used to test the clock-skew code itself. The actual clock-skew check uses the sum of the uncertainty_margin fields of the two clocksource structures being compared. Integer overflow is avoided because the largest computed value of the uncertainty_margin fields is one billion (10^9), and double that value fits into an unsigned int. However, if someone manually specifies (say) UINT_MAX, they will get what they deserve. Note that the refined_jiffies uncertainty_margin field is initialized to TICK_NSEC, which means that skew checks involving this clocksource will be sufficently forgiving. In a similar vein, the clocksource_tsc_early uncertainty_margin field is initialized to 32*NSEC_PER_MSEC, which replicates the current behavior and allows custom setting if needed in order to address the rare skews detected for this clocksource in current mainline. Suggested-by: Thomas Gleixner Signed-off-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Acked-by: Feng Tang Link: https://lore.kernel.org/r/20210527190124.440372-4-paulmck@kernel.org Signed-off-by: Sasha Levin

clocksource: Check per-CPU clock synchronization when marked unstable

2021-07-14T14:56:01Z

[ 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

linux/clocksource.h: Extract common header for vDSO

2020-03-21T14:23:56Z

The vDSO library should only include the necessary headers required for a userspace library (UAPI and a minimal set of kernel headers). To make this possible it is necessary to isolate from the kernel headers the common parts that are strictly necessary to build the library. Split clocksource.h into linux and common headers to make the latter suitable for inclusion in the vDSO library. Signed-off-by: Vincenzo Frascino Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20200320145351.32292-9-vincenzo.frascino@arm.com

lib/vdso: Move VCLOCK_TIMENS to vdso_clock_modes

2020-02-17T19:12:17Z

Move the time namespace indicator clock mode to the other ones for consistency sake. Signed-off-by: Thomas Gleixner Reviewed-by: Vincenzo Frascino Link: https://lkml.kernel.org/r/20200207124403.656097274@linutronix.de

lib/vdso: Cleanup clock mode storage leftovers

2020-02-17T19:12:17Z

Now that all architectures are converted to use the generic storage the helpers and conditionals can be removed. Signed-off-by: Thomas Gleixner Tested-by: Vincenzo Frascino Reviewed-by: Vincenzo Frascino Link: https://lkml.kernel.org/r/20200207124403.470699892@linutronix.de

clocksource: Add common vdso clock mode storage

2020-02-17T13:40:23Z

All architectures which use the generic VDSO code have their own storage for the VDSO clock mode. That's pointless and just requires duplicate code. Provide generic storage for it. The new Kconfig symbol is intermediate and will be removed once all architectures are converted over. Signed-off-by: Thomas Gleixner Tested-by: Vincenzo Frascino Reviewed-by: Vincenzo Frascino Link: https://lkml.kernel.org/r/20200207124403.028046322@linutronix.de

clocksource: Cleanup struct clocksource and documentation

2020-02-17T13:40:22Z

Reformat the struct definition, add missing member documentation. No functional change. Signed-off-by: Thomas Gleixner Reviewed-by: Vincenzo Frascino Link: https://lkml.kernel.org/r/20200207124402.825471920@linutronix.de

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

2018-10-25T18:14:36Z

Pull timekeeping updates from Thomas Gleixner: "The timers and timekeeping departement provides: - Another large y2038 update with further preparations for providing the y2038 safe timespecs closer to the syscalls. - An overhaul of the SHCMT clocksource driver - SPDX license identifier updates - Small cleanups and fixes all over the place" * 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (31 commits) tick/sched : Remove redundant cpu_online() check clocksource/drivers/dw_apb: Add reset control clocksource: Remove obsolete CLOCKSOURCE_OF_DECLARE clocksource/drivers: Unify the names to timer-* format clocksource/drivers/sh_cmt: Add R-Car gen3 support dt-bindings: timer: renesas: cmt: document R-Car gen3 support clocksource/drivers/sh_cmt: Properly line-wrap sh_cmt_of_table[] initializer clocksource/drivers/sh_cmt: Fix clocksource width for 32-bit machines clocksource/drivers/sh_cmt: Fixup for 64-bit machines clocksource/drivers/sh_tmu: Convert to SPDX identifiers clocksource/drivers/sh_mtu2: Convert to SPDX identifiers clocksource/drivers/sh_cmt: Convert to SPDX identifiers clocksource/drivers/renesas-ostm: Convert to SPDX identifiers clocksource: Convert to using %pOFn instead of device_node.name tick/broadcast: Remove redundant check RISC-V: Request newstat syscalls y2038: signal: Change rt_sigtimedwait to use __kernel_timespec y2038: socket: Change recvmmsg to use __kernel_timespec y2038: sched: Change sched_rr_get_interval to use __kernel_timespec y2038: utimes: Rework #ifdef guards for compat syscalls ...

clocksource: Provide clocksource_arch_init()

2018-10-04T21:00:24Z

Architectures have extra archdata in the clocksource, e.g. for VDSO support. There are no sanity checks or general initializations for this available. Add support for that. Signed-off-by: Thomas Gleixner Acked-by: Andy Lutomirski Acked-by: John Stultz Cc: Peter Zijlstra Cc: Matt Rickard Cc: Stephen Boyd Cc: Florian Weimer Cc: "K. Y. Srinivasan" Cc: Vitaly Kuznetsov Cc: devel@linuxdriverproject.org Cc: virtualization@lists.linux-foundation.org Cc: Paolo Bonzini Cc: Arnd Bergmann Cc: Juergen Gross Link: https://lkml.kernel.org/r/20180917130706.973042587@linutronix.de

clocksource: Remove obsolete CLOCKSOURCE_OF_DECLARE

2018-10-03T12:37:02Z

The macro CLOCKSOURCE_OF_DECLARE was renamed more TIMER_OF_DECLARE, and we kept an alias CLOCKSOURCE_OF_DECLARE in order to smooth the transition for drivers. This change was done 1.5 year ago, we can reasonably remove this backward compatible macro as it is no longer used anywhere. Signed-off-by: Daniel Lezcano