Changes in Makefile

2cbb20b0 - tracing: Disable branch profiling in noinstr code

Fri, 21 Mar 2025 19:53:32 +0000

tracing: Disable branch profiling in noinstr codeCONFIG_TRACE_BRANCH_PROFILING inserts a call to ftrace_likely_update()for each use of likely() or unlikely(). That breaks noinstr rules ifthe affected function is annotated as noinstr.Disable branch profiling for files with noinstr functions. In additionto some individual files, this also includes the entire arch/x86subtree, as well as the kernel/entry, drivers/cpuidle, and drivers/idledirectories, all of which are noinstr-heavy.Due to the nature of how sched binaries are built by combining multiple.c files into one, branch profiling is disabled more broadly across thesched code than would otherwise be needed.This fixes many warnings like the following: vmlinux.o: warning: objtool: do_syscall_64+0x40: call to ftrace_likely_update() leaves .noinstr.text section vmlinux.o: warning: objtool: __rdgsbase_inactive+0x33: call to ftrace_likely_update() leaves .noinstr.text section vmlinux.o: warning: objtool: handle_bug.isra.0+0x198: call to ftrace_likely_update() leaves .noinstr.text section ...Reported-by: Ingo Molnar Suggested-by: Steven Rostedt Signed-off-by: Josh Poimboeuf Signed-off-by: Ingo Molnar Acked-by: Thomas Gleixner Cc: Linus Torvalds Link: https://lore.kernel.org/r/fb94fc9303d48a5ed370498f54500cc4c338eb6d.1742586676.git.jpoimboe@kernel.org List of files: /linux-6.15/kernel/time/Makefile

da7bd0a9 - timers: Move sleep() and timeout functions into a separate file

Mon, 14 Oct 2024 08:22:19 +0000

timers: Move *sleep*() and timeout functions into a separate fileAll schedule_timeout() and *sleep*() related functions are interfaces ontop of timer list timers and hrtimers to add a sleep to the code. As theyare built on top of the timer list timers and hrtimers, the [hr]timerinterfaces are already used except when queuing the timer inschedule_timeout(). But there exists the appropriate interface add_timer()which does the same job with an extra check for an already pending timer.Split all those functions as they are into a separate file and useadd_timer() instead of __mod_timer() in schedule_timeout().While at it fix minor formatting issues and a multi line printk functioncall in schedule_timeout().Signed-off-by: Anna-Maria Behnsen Signed-off-by: Thomas Gleixner Acked-by: Frederic Weisbecker Link: https://lore.kernel.org/all/20241014-devel-anna-maria-b4-timers-flseep-v3-2-dc8b907cb62f@linutronix.de List of files: /linux-6.15/kernel/time/Makefile

7ee98877 - timers: Implement the hierarchical pull model

Thu, 22 Feb 2024 10:37:10 +0000

timers: Implement the hierarchical pull modelPlacing timers at enqueue time on a target CPU based on dubious heuristicsdoes not make any sense: 1) Most timer wheel timers are canceled or rearmed before they expire. 2) The heuristics to predict which CPU will be busy when the timer expires are wrong by definition.So placing the timers at enqueue wastes precious cycles.The proper solution to this problem is to always queue the timers on thelocal CPU and allow the non pinned timers to be pulled onto a busy CPU atexpiry time.Therefore split the timer storage into local pinned and global timers:Local pinned timers are always expired on the CPU on which they have beenqueued. Global timers can be expired on any CPU.As long as a CPU is busy it expires both local and global timers. When aCPU goes idle it arms for the first expiring local timer. If the firstexpiring pinned (local) timer is before the first expiring movable timer,then no action is required because the CPU will wake up before the firstmovable timer expires. If the first expiring movable timer is before thefirst expiring pinned (local) timer, then this timer is queued into an idletimerqueue and eventually expired by another active CPU.To avoid global locking the timerqueues are implemented as a hierarchy. Thelowest level of the hierarchy holds the CPUs. The CPUs are associated togroups of 8, which are separated per node. If more than one CPU groupexist, then a second level in the hierarchy collects the groups. Dependingon the size of the system more than 2 levels are required. Each group has a"migrator" which checks the timerqueue during the tick for remote expirabletimers.If the last CPU in a group goes idle it reports the first expiring event inthe group up to the next group(s) in the hierarchy. If the last CPU goesidle it arms its timer for the first system wide expiring timer to ensurethat no timer event is missed.Signed-off-by: Anna-Maria Behnsen Signed-off-by: Thomas Gleixner Reviewed-by: Frederic Weisbecker Link: https://lore.kernel.org/r/20240222103710.32582-1-anna-maria@linutronix.de List of files: /linux-6.15/kernel/time/Makefile

27601055 - time: Improve performance of time64_to_tm()

Tue, 22 Jun 2021 21:36:16 +0000

time: Improve performance of time64_to_tm()The current implementation of time64_to_tm() contains unnecessary loops,branches and look-up tables. The new one uses an arithmetic-based algorithmappeared in [1] and is approximately 3x faster (YMMV).The drawback is that the new code isn't intuitive and contains many 'magicnumbers' (not unusual for this type of algorithm). However, [1] justifiesall those numbers and, given this function's history, the code is unlikelyto need much maintenance, if any at all.Add a KUnit test for it which checks every day in a 160,000 years intervalcentered at 1970-01-01 against the expected result.[1] Neri, Schneider, "Euclidean Affine Functions and Applications toCalendar Algorithms". https://arxiv.org/abs/2102.06959Signed-off-by: Cassio Neri Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20210622213616.313046-1-cassio.neri@gmail.com List of files: /linux-6.15/kernel/time/Makefile

1253b9b8 - clocksource: Provide kernel module to test clocksource watchdog

Thu, 27 May 2021 19:01:23 +0000

clocksource: Provide kernel module to test clocksource watchdogWhen the clocksource watchdog marks a clock as unstable, this mightbe due to that clock being unstable or it might be due to delays thathappen to occur between the reads of the two clocks. It would be goodto have a way of testing the clocksource watchdog's ability todistinguish between these two causes of clock skew and instability.Therefore, provide a new clocksource-wdtest module selected by a newTEST_CLOCKSOURCE_WATCHDOG Kconfig option. This module has a single moduleparameter named "holdoff" that provides the number of seconds of delaybefore testing should start, which defaults to zero when built as a moduleand to 10 seconds when built directly into the kernel. Very large systemsthat boot slowly may need to increase the value of this module parameter.This module uses hand-crafted clocksource structures to do its testing,thus avoiding messing up timing for the rest of the kernel and for userapplications. This module first verifies that the ->uncertainty_marginfield of the clocksource structures are set sanely. It then tests thedelay-detection capability of the clocksource watchdog, increasing thenumber of consecutive delays injected, first provoking console messagescomplaining about the delays and finally forcing a clock-skew event.Unexpected test results cause at least one WARN_ON_ONCE() console splat.If there are no splats, the test has passed. Finally, it fuzzes thevalue returned from a clocksource to test the clocksource watchdog'sability to detect time skew.This module checks the state of its clocksource after each test, anduses WARN_ON_ONCE() to emit a console splat if there are any failures.This should enable all types of test frameworks to detect any suchfailures.This facility is intended for diagnostic use only, and should be avoidedon production systems.Reported-by: Chris Mason Suggested-by: Thomas Gleixner Signed-off-by: Paul E. McKenney Signed-off-by: Thomas Gleixner Tested-by: Feng Tang Link: https://lore.kernel.org/r/20210527190124.440372-5-paulmck@kernel.org List of files: /linux-6.15/kernel/time/Makefile

b3550164 - timekeeping: add CONFIG_LEGACY_TIMER_TICK

Thu, 24 Sep 2020 13:21:43 +0000

timekeeping: add CONFIG_LEGACY_TIMER_TICKAll platforms that currently do not use generic clockevents roughly callthe same set of functions in their timer interrupts: xtime_update(),update_process_times() and profile_tick(), sometimes in a differentsequence.Add a helper function that performs all three of them, to make thecallers more uniform and simplify the interface.Reviewed-by: Geert Uytterhoeven Reviewed-by: Linus Walleij Signed-off-by: Arnd Bergmann List of files: /linux-6.15/kernel/time/Makefile

769071ac - ns: Introduce Time Namespace

Tue, 12 Nov 2019 01:26:52 +0000

ns: Introduce Time NamespaceTime Namespace isolates clock values.The kernel provides access to several clocks CLOCK_REALTIME,CLOCK_MONOTONIC, CLOCK_BOOTTIME, etc.CLOCK_REALTIME System-wide clock that measures real (i.e., wall-clock) time.CLOCK_MONOTONIC Clock that cannot be set and represents monotonic time since some unspecified starting point.CLOCK_BOOTTIME Identical to CLOCK_MONOTONIC, except it also includes any time that the system is suspended.For many users, the time namespace means the ability to changes date andtime in a container (CLOCK_REALTIME). Providing per namespace notions ofCLOCK_REALTIME would be complex with a massive overhead, but has a dubiousvalue.But in the context of checkpoint/restore functionality, monotonic andboottime clocks become interesting. Both clocks are monotonic withunspecified starting points. These clocks are widely used to measure timeslices and set timers. After restoring or migrating processes, it has to beguaranteed that they never go backward. In an ideal case, the behavior ofthese clocks should be the same as for a case when a whole system issuspended. All this means that it is required to set CLOCK_MONOTONIC andCLOCK_BOOTTIME clocks, which can be achieved by adding per-namespaceoffsets for clocks.A time namespace is similar to a pid namespace in the way how it iscreated: unshare(CLONE_NEWTIME) system call creates a new time namespace,but doesn't set it to the current process. Then all children of the processwill be born in the new time namespace, or a process can use the setns()system call to join a namespace.This scheme allows setting clock offsets for a namespace, before anyprocesses appear in it.All available clone flags have been used, so CLONE_NEWTIME uses the highestbit of CSIGNAL. It means that it can be used only with the unshare() andthe clone3() system calls.[ tglx: Adjusted paragraph about clone3() to reality and massaged the changelog a bit. ]Co-developed-by: Dmitry Safonov Signed-off-by: Andrei Vagin Signed-off-by: Dmitry Safonov Signed-off-by: Thomas Gleixner Link: https://criu.org/Time_namespaceLink: https://lists.openvz.org/pipermail/criu/2018-June/041504.htmlLink: https://lore.kernel.org/r/20191112012724.250792-4-dima@arista.com List of files: /linux-6.15/kernel/time/Makefile

44f57d78 - timekeeping: Provide a generic update_vsyscall() implementation

Fri, 21 Jun 2019 09:52:30 +0000

timekeeping: Provide a generic update_vsyscall() implementationThe new generic VDSO library allows to unify the update_vsyscall[_tz]()implementations.Provide a generic implementation based on the x86 code and the bindingswhich need to be implemented in architecture specific code.[ tglx: Moved it into kernel/time where it belongs. Removed the pointless line breaks in the stub functions. Massaged changelog ]Signed-off-by: Vincenzo Frascino Signed-off-by: Thomas Gleixner Tested-by: Shijith Thotton Tested-by: Andre Przywara Cc: linux-arch@vger.kernel.orgCc: linux-arm-kernel@lists.infradead.orgCc: linux-mips@vger.kernel.orgCc: linux-kselftest@vger.kernel.orgCc: Catalin Marinas Cc: Will Deacon Cc: Arnd Bergmann Cc: Russell King Cc: Ralf Baechle Cc: Paul Burton Cc: Daniel Lezcano Cc: Mark Salyzyn Cc: Peter Collingbourne Cc: Shuah Khan Cc: Dmitry Safonov <0x7f454c46@gmail.com>Cc: Rasmus Villemoes Cc: Huw Davies Link: https://lkml.kernel.org/r/20190621095252.32307-4-vincenzo.frascino@arm.com List of files: /linux-6.15/kernel/time/Makefile

b2441318 - License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Wed, 01 Nov 2017 14:07:57 +0000

License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseMany source files in the tree are missing licensing information, whichmakes it harder for compliance tools to determine the correct license.By default all files without license information are under the defaultlicense 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 bindingshorthand, which can be used instead of the full boiler plate text.This patch is based on work done by Thomas Gleixner and Kate Stewart andPhilippe Ombredanne.How this work was done:Patches were generated and checked against linux-4.14-rc6 for a subset ofthe 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 caseswhere non-standard license headers were used, and references to licensehad to be inferred by heuristics based on keywords.The analysis to determine which SPDX License Identifier to be applied toa file was done in a spreadsheet of side by side results from of theoutput of two independent scanners (ScanCode & Windriver) producing SPDXtag:value files created by Philippe Ombredanne. Philippe prepared thebase 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 filesassessed. Kate Stewart did a file by file comparison of the scannerresults in the spreadsheet to determine which SPDX license identifier(s)to be applied to the file. She confirmed any determination that was notimmediately 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 licenseidentifiers 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 thespreadsheet to determine the SPDX license identifiers to apply to thesource files by Kate, Philippe, Thomas and, in some cases, confirmationby lawyers working with the Linux Foundation.Kate also obtained a third independent scan of the 4.13 code base fromFOSSology, and compared selected files where the other two scannersdisagreed against that SPDX file, to see if there was new insights. TheWindriver scanner is based on an older version of FOSSology in part, sothey are related.Thomas did random spot checks in about 500 files from the spreadsheetsfor the uapi headers and agreed with SPDX license identifier in thefiles he inspected. For the non-uapi files Thomas did random spot checksin about 15000 files.In initial set of patches against 4.14-rc6, 3 files were found to havecopy/paste license identifier errors, and have been fixed to reflect thecorrect identifier.Additionally Philippe spent 10 hours this week doing a detailed manualinspection and review of the 12,461 patched files from the initial patchversion 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 correctThis produced a worksheet with 20 files needing minor correction. Thisworksheet was then exported into 3 different .csv files for thedifferent types of files to be modified.These .csv files were then reviewed by Greg. Thomas wrote a script toparse the csv files and add the proper SPDX tag to the file, in theformat that the file expected. This script was further refined by Gregbased on the output to detect more types of files automatically and todistinguish between header and source .c files (which need differentcomment types.) Finally Greg ran the script using the .csv files togenerate the patches.Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman List of files: /linux-6.15/kernel/time/Makefile

dfb4357d - time: Remove CONFIG_TIMER_STATS

Wed, 08 Feb 2017 19:26:59 +0000

time: Remove CONFIG_TIMER_STATSCurrently CONFIG_TIMER_STATS exposes process information across namespaces:kernel/time/timer_list.c print_timer(): SEQ_printf(m, ", %s/%d", tmp, timer->start_pid);/proc/timer_list: #11: <0000000000000000>, hrtimer_wakeup, S:01, do_nanosleep, cron/2570Given that the tracer can give the same information, this patch entirelyremoves CONFIG_TIMER_STATS.Suggested-by: Thomas Gleixner Signed-off-by: Kees Cook Acked-by: John Stultz Cc: Nicolas Pitre Cc: linux-doc@vger.kernel.orgCc: Lai Jiangshan Cc: Shuah Khan Cc: Xing Gao Cc: Jonathan Corbet Cc: Jessica Frazelle Cc: kernel-hardening@lists.openwall.comCc: Nicolas Iooss Cc: "Paul E. McKenney" Cc: Petr Mladek Cc: Richard Cochran Cc: Tejun Heo Cc: Michal Marek Cc: Josh Poimboeuf Cc: Dmitry Vyukov Cc: Oleg Nesterov Cc: "Eric W. Biederman" Cc: Olof Johansson Cc: Andrew Morton Cc: linux-api@vger.kernel.orgCc: Arjan van de Ven Link: http://lkml.kernel.org/r/20170208192659.GA32582@beastSigned-off-by: Thomas Gleixner List of files: /linux-6.15/kernel/time/Makefile

baa73d9e - posix-timers: Make them configurable

Fri, 11 Nov 2016 05:10:10 +0000

posix-timers: Make them configurableSome embedded systems have no use for them. This removes about25KB from the kernel binary size when configured out.Corresponding syscalls are routed to a stub logging the attempt touse those syscalls which should be enough of a clue if they weredisabled without proper consideration. They are: timer_create,timer_gettime: timer_getoverrun, timer_settime, timer_delete,clock_adjtime, setitimer, getitimer, alarm.The clock_settime, clock_gettime, clock_getres and clock_nanosleepsyscalls are replaced by simple wrappers compatible with CLOCK_REALTIME,CLOCK_MONOTONIC and CLOCK_BOOTTIME only which should cover the vastmajority of use cases with very little code.Signed-off-by: Nicolas Pitre Acked-by: Richard Cochran Acked-by: Thomas Gleixner Acked-by: John Stultz Reviewed-by: Josh Triplett Cc: Paul Bolle Cc: linux-kbuild@vger.kernel.orgCc: netdev@vger.kernel.orgCc: Michal Marek Cc: Edward Cree Link: http://lkml.kernel.org/r/1478841010-28605-7-git-send-email-nicolas.pitre@linaro.orgSigned-off-by: Thomas Gleixner List of files: /linux-6.15/kernel/time/Makefile

65f26062 - time: Remove development rules from Kbuild/Makefile

Wed, 01 Jul 2015 07:57:35 +0000

time: Remove development rules from Kbuild/Makefiletime.o gets rebuilt unconditionally due to a leftover Makefile rulewhich was placed there for development purposes.Remove it along with the commented out always rule in the toplevelKbuild file.Fixes: 0a227985d4a9 'time: Move timeconst.h into include/generated'Reported-by; Stephen Boyd Signed-off-by: Thomas Gleixner Cc: Nicholas Mc Guire List of files: /linux-6.15/kernel/time/Makefile

0a227985 - time: Move timeconst.h into include/generated

Mon, 18 May 2015 12:19:12 +0000

time: Move timeconst.h into include/generatedkernel/time/timeconst.h is moved to include/generated/ and generated by the top level Kbuild. This allows using timeconst.h in an earlierbuild stage.Signed-off-by: Nicholas Mc Guire Cc: Masahiro Yamada Cc: Sam Ravnborg Cc: Joe Perches Cc: John Stultz Cc: Andrew Hunter Cc: Paul Turner Cc: Michal Marek Link: http://lkml.kernel.org/r/1431951554-5563-1-git-send-email-hofrat@osadl.orgSigned-off-by: Thomas Gleixner List of files: /linux-6.15/kernel/time/Makefile

9f083b74 - clockevents: Remove CONFIG_GENERIC_CLOCKEVENTS_BUILD

Wed, 25 Mar 2015 12:05:19 +0000

clockevents: Remove CONFIG_GENERIC_CLOCKEVENTS_BUILDThis option was for simpler migration to the clock events code.Most architectures have been converted and the option has beendisfunctional as a standalone option for quite some time. Removeit.Signed-off-by: Thomas Gleixner Signed-off-by: Rafael J. Wysocki Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/5021859.jl9OC1medj@vostro.rjw.lanSigned-off-by: Ingo Molnar List of files: /linux-6.15/kernel/time/Makefile

74d23cc7 - time: move the timecounter/cyclecounter code into its own file.

Sun, 21 Dec 2014 18:46:56 +0000

time: move the timecounter/cyclecounter code into its own file.The timecounter code has almost nothing to do with the clocksourcecode. Let it live in its own file. This will help isolate thetimecounter users from the clocksource users in the source tree.Signed-off-by: Richard Cochran Acked-by: Jeff Kirsher Signed-off-by: David S. Miller List of files: /linux-6.15/kernel/time/Makefile

fd866e2b - time: Rename udelay_test.c to test_udelay.c

Mon, 04 Aug 2014 18:30:56 +0000

time: Rename udelay_test.c to test_udelay.cKees requested that this test module be renamed for consistency sake,so this patch renames the udelay_test.c file (recently added totip/timers/core for 3.17) to test_udelay.cCc: Kees Cook Cc: Greg KH Cc: Stephen Rothwell Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Linux-Next Cc: David Riley Signed-off-by: John Stultz List of files: /linux-6.15/kernel/time/Makefile

e704f93a - kernel: time: Add udelay_test module to validate udelay

Mon, 16 Jun 2014 21:58:32 +0000

kernel: time: Add udelay_test module to validate udelayCreate a module that allows udelay() to be executed to ensure thatit is delaying at least as long as requested (with a little bit oferror allowed).There are some configurations which don't have reliably udelaydue to using a loop delay with cpufreq changes which should usea counter time based delay instead. This test aims to identifythose configurations where timing is unreliable.Signed-off-by: David Riley Signed-off-by: John Stultz List of files: /linux-6.15/kernel/time/Makefile

5cee9645 - time/timers: Move all time(r) related files into kernel/time

Sun, 22 Jun 2014 10:06:40 +0000

time/timers: Move all time(r) related files into kernel/timeExcept for Kconfig.HZ. That needs a separate treatment.Signed-off-by: Thomas Gleixner List of files: /linux-6.15/kernel/time/Makefile

849401b6 - tick: Fixup more fallout from hrtimer broadcast mode

Sun, 09 Feb 2014 06:02:22 +0000

tick: Fixup more fallout from hrtimer broadcast modeThe hrtimer mode of broadcast is supported only whenGENERIC_CLOCKEVENTS_BROADCAST and TICK_ONESHOT config optionsare enabled. Hence compile in the functions for hrtimer modeof broadcast only when these options are selected.Also fix max_delta_ticks value for the pseudo clock device.Reported-by: Fengguang Wu Reported-by: Ingo Molnar Signed-off-by: Preeti U Murthy Link: http://lkml.kernel.org/r/52F719EE.9010304@linux.vnet.ibm.comSigned-off-by: Thomas Gleixner List of files: /linux-6.15/kernel/time/Makefile

5d1638ac - tick: Introduce hrtimer based broadcast

Fri, 07 Feb 2014 08:06:32 +0000

tick: Introduce hrtimer based broadcastOn some architectures, in certain CPU deep idle states the local timers stop.An external clock device is used to wakeup these CPUs. The kernel support for thewakeup of these CPUs is provided by the tick broadcast framework by using theexternal clock device as the wakeup source.However not all implementations of architectures provide such an externalclock device. This patch includes support in the broadcast framework to handlethe wakeup of the CPUs in deep idle states on such systems by queuing a hrtimeron one of the CPUs, which is meant to handle the wakeup of CPUs in deep idle states.This patchset introduces a pseudo clock device which can be registered by thearchs as tick_broadcast_device in the absence of a real external clockdevice. Once registered, the broadcast framework will work as is for thesearchitectures as long as the archs take care of the BROADCAST_ENTERnotification failing for one of the CPUs. This CPU is made the stand by CPU tohandle wakeup of the CPUs in deep idle and it *must not enter deep idle states*.The CPU with the earliest wakeup is chosen to be this CPU. Hence this way thestand by CPU dynamically moves around and so does the hrtimer which is queuedto trigger at the next earliest wakeup time. This is consistent with the case wherean external clock device is present. The smp affinity of this clock device isset to the CPU with the earliest wakeup. This patchset handles the hotplug ofthe stand by CPU as well by moving the hrtimer on to the CPU handling the CPU_DEADnotification.Originally-from: Thomas Gleixner Signed-off-by: Preeti U Murthy Cc: deepthi@linux.vnet.ibm.comCc: paulmck@linux.vnet.ibm.comCc: fweisbec@gmail.comCc: paulus@samba.orgCc: srivatsa.bhat@linux.vnet.ibm.comCc: svaidy@linux.vnet.ibm.comCc: peterz@infradead.orgCc: benh@kernel.crashing.orgCc: rafael.j.wysocki@intel.comCc: linuxppc-dev@lists.ozlabs.orgLink: http://lkml.kernel.org/r/20140207080632.17187.80532.stgit@preeti.in.ibm.comSigned-off-by: Thomas Gleixner List of files: /linux-6.15/kernel/time/Makefile