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* watchdog: fix barriers when printing backtraces from all CPUsPetr Mladek2021-05-191-11/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 9f113bf760ca90d709f8f89a733d10abb1f04a83 ] Any parallel softlockup reports are skipped when one CPU is already printing backtraces from all CPUs. The exclusive rights are synchronized using one bit in soft_lockup_nmi_warn. There is also one memory barrier that does not make much sense. Use two barriers on the right location to prevent mixing two reports. [pmladek@suse.com: use bit lock operations to prevent multiple soft-lockup reports] Link: https://lkml.kernel.org/r/YFSVsLGVWMXTvlbk@alley Link: https://lkml.kernel.org/r/20210311122130.6788-6-pmladek@suse.com Signed-off-by: Petr Mladek <pmladek@suse.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Laurence Oberman <loberman@redhat.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vincent Whitchurch <vincent.whitchurch@axis.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
* watchdog/softlockup: remove logic that tried to prevent repeated reportsPetr Mladek2021-05-191-12/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 1bc503cb4a2638fb1c57801a7796aca57845ce63 ] The softlockup detector does some gymnastic with the variable soft_watchdog_warn. It was added by the commit 58687acba59266735ad ("lockup_detector: Combine nmi_watchdog and softlockup detector"). The purpose is not completely clear. There are the following clues. They describe the situation how it looked after the above mentioned commit: 1. The variable was checked with a comment "only warn once". 2. The variable was set when softlockup was reported. It was cleared only when the CPU was not longer in the softlockup state. 3. watchdog_touch_ts was not explicitly updated when the softlockup was reported. Without this variable, the report would normally be printed again during every following watchdog_timer_fn() invocation. The logic has got even more tangled up by the commit ed235875e2ca98 ("kernel/watchdog.c: print traces for all cpus on lockup detection"). After this commit, soft_watchdog_warn is set only when softlockup_all_cpu_backtrace is enabled. But multiple reports from all CPUs are prevented by a new variable soft_lockup_nmi_warn. Conclusion: The variable probably never worked as intended. In each case, it has not worked last many years because the softlockup was reported repeatedly after the full period defined by watchdog_thresh. The reason is that watchdog gets touched in many known slow paths, for example, in printk_stack_address(). This code is called also when printing the softlockup report. It means that the watchdog timestamp gets updated after each report. Solution: Simply remove the logic. People want the periodic report anyway. Link: https://lkml.kernel.org/r/20210311122130.6788-5-pmladek@suse.com Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Laurence Oberman <loberman@redhat.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vincent Whitchurch <vincent.whitchurch@axis.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
* watchdog: explicitly update timestamp when reporting softlockupPetr Mladek2021-05-191-0/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit c9ad17c991492f4390f42598f6ab0531f87eed07 ] The softlockup situation might stay for a long time or even forever. When it happens, the softlockup debug messages are printed in regular intervals defined by get_softlockup_thresh(). There is a mystery. The repeated message is printed after the full interval that is defined by get_softlockup_thresh(). But the timer callback is called more often as defined by sample_period. The code looks like the soflockup should get reported in every sample_period when it was once behind the thresh. It works only by chance. The watchdog is touched when printing the stall report, for example, in printk_stack_address(). Make the behavior clear and predictable by explicitly updating the timestamp in watchdog_timer_fn() when the report gets printed. Link: https://lkml.kernel.org/r/20210311122130.6788-3-pmladek@suse.com Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Laurence Oberman <loberman@redhat.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vincent Whitchurch <vincent.whitchurch@axis.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
* watchdog: rename __touch_watchdog() to a better descriptive namePetr Mladek2021-05-191-4/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 7c0012f522c802d25be102bafe54f333168e6119 ] Patch series "watchdog/softlockup: Report overall time and some cleanup", v2. I dug deep into the softlockup watchdog history when time permitted this year. And reworked the patchset that fixed timestamps and cleaned up the code[2]. I split it into very small steps and did even more code clean up. The result looks quite strightforward and I am pretty confident with the changes. [1] v2: https://lore.kernel.org/r/20201210160038.31441-1-pmladek@suse.com [2] v1: https://lore.kernel.org/r/20191024114928.15377-1-pmladek@suse.com This patch (of 6): There are many touch_*watchdog() functions. They are called in situations where the watchdog could report false positives or create unnecessary noise. For example, when CPU is entering idle mode, a virtual machine is stopped, or a lot of messages are printed in the atomic context. These functions set SOFTLOCKUP_RESET instead of a real timestamp. It allows to call them even in a context where jiffies might be outdated. For example, in an atomic context. The real timestamp is set by __touch_watchdog() that is called from the watchdog timer callback. Rename this callback to update_touch_ts(). It better describes the effect and clearly distinguish is from the other touch_*watchdog() functions. Another motivation is that two timestamps are going to be used. One will be used for the total softlockup time. The other will be used to measure time since the last report. The new function name will help to distinguish which timestamp is being updated. Link: https://lkml.kernel.org/r/20210311122130.6788-1-pmladek@suse.com Link: https://lkml.kernel.org/r/20210311122130.6788-2-pmladek@suse.com Signed-off-by: Petr Mladek <pmladek@suse.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Laurence Oberman <loberman@redhat.com> Cc: Vincent Whitchurch <vincent.whitchurch@axis.com> Cc: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
* kernel/watchdog: fix watchdog_allowed_mask not used warningSantosh Sivaraj2020-11-141-2/+2
| | | | | | | | | | | | Define watchdog_allowed_mask only when SOFTLOCKUP_DETECTOR is enabled. Fixes: 7feeb9cd4f5b ("watchdog/sysctl: Clean up sysctl variable name space") Signed-off-by: Santosh Sivaraj <santosh@fossix.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20201106015025.1281561-1-santosh@fossix.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliasesGuilherme G. Piccoli2020-06-081-28/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | After a recent change introduced by Vlastimil's series [0], kernel is able now to handle sysctl parameters on kernel command line; also, the series introduced a simple infrastructure to convert legacy boot parameters (that duplicate sysctls) into sysctl aliases. This patch converts the watchdog parameters softlockup_panic and {hard,soft}lockup_all_cpu_backtrace to use the new alias infrastructure. It fixes the documentation too, since the alias only accepts values 0 or 1, not the full range of integers. We also took the opportunity here to improve the documentation of the previously converted hung_task_panic (see the patch series [0]) and put the alias table in alphabetical order. [0] http://lkml.kernel.org/r/20200427180433.7029-1-vbabka@suse.cz Signed-off-by: Guilherme G. Piccoli <gpiccoli@canonical.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Kees Cook <keescook@chromium.org> Cc: Iurii Zaikin <yzaikin@google.com> Cc: Luis Chamberlain <mcgrof@kernel.org> Link: http://lkml.kernel.org/r/20200507214624.21911-1-gpiccoli@canonical.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* sysctl: pass kernel pointers to ->proc_handlerChristoph Hellwig2020-04-271-6/+6
| | | | | | | | | | | | | | | Instead of having all the sysctl handlers deal with user pointers, which is rather hairy in terms of the BPF interaction, copy the input to and from userspace in common code. This also means that the strings are always NUL-terminated by the common code, making the API a little bit safer. As most handler just pass through the data to one of the common handlers a lot of the changes are mechnical. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Andrey Ignatov <rdna@fb.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* watchdog/softlockup: Enforce that timestamp is valid on bootThomas Gleixner2020-01-171-4/+6
| | | | | | | | | | | | | | | | | | | | Robert reported that during boot the watchdog timestamp is set to 0 for one second which is the indicator for a watchdog reset. The reason for this is that the timestamp is in seconds and the time is taken from sched clock and divided by ~1e9. sched clock starts at 0 which means that for the first second during boot the watchdog timestamp is 0, i.e. reset. Use ULONG_MAX as the reset indicator value so the watchdog works correctly right from the start. ULONG_MAX would only conflict with a real timestamp if the system reaches an uptime of 136 years on 32bit and almost eternity on 64bit. Reported-by: Robert Richter <rrichter@marvell.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/87o8v3uuzl.fsf@nanos.tec.linutronix.de
* watchdog/softlockup: Remove obsolete check of last reported taskPetr Mladek2020-01-161-17/+1
| | | | | | | | | | | | | | | | | commit 9cf57731b63e ("watchdog/softlockup: Replace "watchdog/%u" threads with cpu_stop_work") ensures that the watchdog is reliably touched during a task switch. As a result the check for an unnoticed task switch is not longer needed. Remove the relevant code, which effectively reverts commit b1a8de1f5343 ("softlockup: make detector be aware of task switch of processes hogging cpu") Signed-off-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Ziljstra <peterz@infradead.org> Link: https://lore.kernel.org/r/20191024114928.15377-2-pmladek@suse.com
* watchdog: Remove soft_lockup_hrtimer_cnt and related codeJisheng Zhang2020-01-161-3/+0
| | | | | | | | | | | After commit 9cf57731b63e ("watchdog/softlockup: Replace "watchdog/%u" threads with cpu_stop_work"), the percpu soft_lockup_hrtimer_cnt is not used any more, so remove it and related code. Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lore.kernel.org/r/20191218131720.4146aea2@xhacker.debian
* watchdog: Mark watchdog_hrtimer to expire in hard interrupt contextSebastian Andrzej Siewior2019-08-011-2/+2
| | | | | | | | | | | | | | | | | | The watchdog hrtimer must expire in hard interrupt context even on PREEMPT_RT=y kernels as otherwise the hard/softlockup detection logic would not work. No functional change. [ tglx: Split out from larger combo patch. Added changelog ] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20190726185753.262895510@linutronix.de
* watchdog: Fix typo in commentArash Fotouhi2019-04-181-1/+1
| | | | | | | | | | | Signed-off-by: Arash Fotouhi <arash@arashfotouhi.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: loberman@redhat.com Cc: vincent.whitchurch@axis.com Link: http://lkml.kernel.org/r/1553308112-3513-1-git-send-email-arash@arashfotouhi.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog: Respect watchdog cpumask on CPU hotplugThomas Gleixner2019-03-281-2/+4
| | | | | | | | | | | | | | | | | | | | | | | | | The rework of the watchdog core to use cpu_stop_work broke the watchdog cpumask on CPU hotplug. The watchdog_enable/disable() functions are now called unconditionally from the hotplug callback, i.e. even on CPUs which are not in the watchdog cpumask. As a consequence the watchdog can become unstoppable. Only invoke them when the plugged CPU is in the watchdog cpumask. Fixes: 9cf57731b63e ("watchdog/softlockup: Replace "watchdog/%u" threads with cpu_stop_work") Reported-by: Maxime Coquelin <maxime.coquelin@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Maxime Coquelin <maxime.coquelin@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Don Zickus <dzickus@redhat.com> Cc: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/alpine.DEB.2.21.1903262245490.1789@nanos.tec.linutronix.de
* watchdog/core: Make variables staticValdis Kletnieks2019-03-221-2/+2
| | | | | | | | | | | | | | | | | sparse complains: CHECK kernel/watchdog.c kernel/watchdog.c:45:19: warning: symbol 'nmi_watchdog_available' was not declared. Should it be static? kernel/watchdog.c:47:16: warning: symbol 'watchdog_allowed_mask' was not declared. Should it be static? They're not referenced by name from anyplace else, make them static. Signed-off-by: Valdis Kletnieks <valdis.kletnieks@vt.edu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/7855.1552383228@turing-police
* watchdog/core: Add watchdog_thresh command line parameterLaurence Oberman2018-11-011-0/+7
| | | | | | | | | | | | | | | | | | | | | | The hard and soft lockup detector threshold has a default value of 10 seconds which can only be changed via sysctl. During early boot lockup detection can trigger when noisy debugging emits a large amount of messages to the console, but there is no way to set a larger threshold on the kernel command line. The detector can only be completely disabled. Add a new watchdog_thresh= command line parameter to allow boot time control over the threshold. It works in the same way as the sysctl and affects both the soft and the hard lockup detectors. Signed-off-by: Laurence Oberman <loberman@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: rdunlap@infradead.org Cc: prarit@redhat.com Link: https://lkml.kernel.org/r/1541079018-13953-1-git-send-email-loberman@redhat.com
* watchdog: Mark watchdog touch functions as notraceVincent Whitchurch2018-08-301-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | Some architectures need to use stop_machine() to patch functions for ftrace, and the assumption is that the stopped CPUs do not make function calls to traceable functions when they are in the stopped state. Commit ce4f06dcbb5d ("stop_machine: Touch_nmi_watchdog() after MULTI_STOP_PREPARE") added calls to the watchdog touch functions from the stopped CPUs and those functions lack notrace annotations. This leads to crashes when enabling/disabling ftrace on ARM kernels built with the Thumb-2 instruction set. Fix it by adding the necessary notrace annotations. Fixes: ce4f06dcbb5d ("stop_machine: Touch_nmi_watchdog() after MULTI_STOP_PREPARE") Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: oleg@redhat.com Cc: tj@kernel.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180821152507.18313-1-vincent.whitchurch@axis.com
* watchdog/softlockup: Fix cpu_stop_queue_work() double-queue bugPeter Zijlstra2018-07-151-5/+15
| | | | | | | | | | | | | | | | | | | When scheduling is delayed for longer than the softlockup interrupt period it is possible to double-queue the cpu_stop_work, causing list corruption. Cure this by adding a completion to track the cpu_stop_work's progress. Reported-by: kernel test robot <lkp@intel.com> Tested-by: Rong Chen <rong.a.chen@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 9cf57731b63e ("watchdog/softlockup: Replace "watchdog/%u" threads with cpu_stop_work") Link: http://lkml.kernel.org/r/20180713104208.GW2494@hirez.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/softlockup: Replace "watchdog/%u" threads with cpu_stop_workPeter Zijlstra2018-07-031-77/+60
| | | | | | | | | | | | | | | | | | Oleg suggested to replace the "watchdog/%u" threads with cpu_stop_work. That removes one thread per CPU while at the same time fixes softlockup vs SCHED_DEADLINE. But more importantly, it does away with the single smpboot_update_cpumask_percpu_thread() user, which allows cleanups/shrinkage of the smpboot interface. Suggested-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* Merge branch 'linus' into sched/core, to pick up fixesIngo Molnar2017-11-081-0/+1
|\ | | | | | | Signed-off-by: Ingo Molnar <mingo@kernel.org>
| * 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>
* | sched/isolation: Introduce housekeeping flagsFrederic Weisbecker2017-10-271-1/+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, watchdog: Use housekeeping_cpumask() instead of ad-hoc versionFrederic Weisbecker2017-10-271-8/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | While trying to disable the watchog on nohz_full CPUs, the watchdog implements an ad-hoc version of housekeeping_cpumask(). Lets replace those re-invented lines. 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/1509072159-31808-3-git-send-email-frederic@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
* | sched/isolation: Move housekeeping related code to its own fileFrederic Weisbecker2017-10-271-0/+1
|/ | | | | | | | | | | | | | | | | | | | 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>
* watchdog/core: Put softlockup_threads_initialized under ifdef guardThomas Gleixner2017-10-041-1/+1
| | | | | | The variable is unused when the softlockup detector is disabled in Kconfig. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
* watchdog/core: Rename some softlockup_* functionsThomas Gleixner2017-10-041-9/+9
| | | | | | | | | | | | | | | | The function names made sense up to the point where the watchdog (re)configuration was unified to use softlockup_reconfigure_threads() for all configuration purposes. But that includes scenarios which solely configure the nmi watchdog. Rename softlockup_reconfigure_threads() and softlockup_init_threads() so the function names match the functionality. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Linus Torvalds <torvalds@linuxfoundation.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Don Zickus <dzickus@redhat.com>
* powerpc/watchdog: Make use of watchdog_nmi_probe()Thomas Gleixner2017-10-041-1/+4
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The rework of the core hotplug code triggers the WARN_ON in start_wd_cpu() on powerpc because it is called multiple times for the boot CPU. The first call is via: start_wd_on_cpu+0x80/0x2f0 watchdog_nmi_reconfigure+0x124/0x170 softlockup_reconfigure_threads+0x110/0x130 lockup_detector_init+0xbc/0xe0 kernel_init_freeable+0x18c/0x37c kernel_init+0x2c/0x160 ret_from_kernel_thread+0x5c/0xbc And then again via the CPU hotplug registration: start_wd_on_cpu+0x80/0x2f0 cpuhp_invoke_callback+0x194/0x620 cpuhp_thread_fun+0x7c/0x1b0 smpboot_thread_fn+0x290/0x2a0 kthread+0x168/0x1b0 ret_from_kernel_thread+0x5c/0xbc This can be avoided by setting up the cpu hotplug state with nocalls and move the initialization to the watchdog_nmi_probe() function. That initializes the hotplug callbacks without invoking the callback and the following core initialization function then configures the watchdog for the online CPUs (in this case CPU0) via softlockup_reconfigure_threads(). Reported-and-tested-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: linuxppc-dev@lists.ozlabs.org
* watchdog/core, powerpc: Lock cpus across reconfigurationThomas Gleixner2017-10-041-1/+9
| | | | | | | | | | | | | | | | | Instead of dropping the cpu hotplug lock after stopping NMI watchdog and threads and reaquiring for restart, the code and the protection rules become more obvious when holding cpu hotplug lock across the full reconfiguration. Suggested-by: Linus Torvalds <torvalds@linuxfoundation.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Don Zickus <dzickus@redhat.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1710022105570.2114@nanos
* watchdog/core, powerpc: Replace watchdog_nmi_reconfigure()Thomas Gleixner2017-10-041-15/+18
| | | | | | | | | | | | | | | | | | | | | | The recent cleanup of the watchdog code split watchdog_nmi_reconfigure() into two stages. One to stop the NMI and one to restart it after reconfiguration. That was done by adding a boolean 'run' argument to the code, which is functionally correct but not necessarily a piece of art. Replace it by two explicit functions: watchdog_nmi_stop() and watchdog_nmi_start(). Fixes: 6592ad2fcc8f ("watchdog/core, powerpc: Make watchdog_nmi_reconfigure() two stage") Requested-by: Linus 'Nursing his pet-peeve' Torvalds <torvalds@linuxfoundation.org> Signed-off-by: Thomas 'Mopping up garbage' Gleixner <tglx@linutronix.de> Acked-by: Michael Ellerman <mpe@ellerman.id.au> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Don Zickus <dzickus@redhat.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1710021957480.2114@nanos
* watchdog/hardlockup: Clean up hotplug locking messThomas Gleixner2017-09-141-6/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | All watchdog thread related functions are delegated to the smpboot thread infrastructure, which handles serialization against CPU hotplug correctly. The sysctl interface is completely decoupled from anything which requires CPU hotplug protection. No need to protect the sysctl writes against cpu hotplug anymore. Remove it and add the now required protection to the powerpc arch_nmi_watchdog implementation. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/20170912194148.418497420@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/hardlockup/perf: Use new perf CPU enable mechanismThomas Gleixner2017-09-141-1/+3
| | | | | | | | | | | | | | | | | | | | | Get rid of the hodgepodge which tries to be smart about perf being unavailable and error printout rate limiting. That's all not required simply because this is never invoked when the perf NMI watchdog is not functional. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194148.259651788@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/hardlockup/perf: Implement init time detection of perfThomas Gleixner2017-09-141-1/+12
| | | | | | | | | | | | | | | | | | | Use the init time detection of the perf NMI watchdog to determine whether the perf NMI watchdog is functional. If not disable it permanentely. It won't come back magically at runtime. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194148.099799541@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Get rid of the racy update loopThomas Gleixner2017-09-141-48/+47
| | | | | | | | | | | | | | | | | | | | | | Letting user space poke directly at variables which are used at run time is stupid and causes a lot of race conditions and other issues. Seperate the user variables and on change invoke the reconfiguration, which then stops the watchdogs, reevaluates the new user value and restarts the watchdogs with the new parameters. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194147.939985640@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core, powerpc: Make watchdog_nmi_reconfigure() two stageThomas Gleixner2017-09-141-9/+22
| | | | | | | | | | | | | | | | | | | | | | | | | | | | Both the perf reconfiguration and the powerpc watchdog_nmi_reconfigure() need to be done in two steps. 1) Stop all NMIs 2) Read the new parameters and start NMIs Right now watchdog_nmi_reconfigure() is a combination of both. To allow a clean reconfiguration add a 'run' argument and split the functionality in powerpc. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/20170912194147.862865570@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/sysctl: Clean up sysctl variable name spaceThomas Gleixner2017-09-141-21/+20
| | | | | | | | | | | | | | | | | | Reflect that these variables are user interface related and remove the whitespace damage in the sysctl table while at it. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194147.783210221@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Further simplify sysctl handlingThomas Gleixner2017-09-141-20/+7
| | | | | | | | | | | | | | | | | | | | Use a single function to update sysctl changes. This is not a high frequency user space interface and it's root only. Preparatory patch to cleanup the sysctl variable handling. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194147.549114957@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Get rid of the thread teardown/setup danceThomas Gleixner2017-09-141-171/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The lockup detector reconfiguration tears down all watchdog threads when the watchdog is disabled and sets them up again when its enabled. That's a pointless exercise. The watchdog threads are not consuming an insane amount of resources, so it's enough to set them up at init time and keep them in parked position when the watchdog is disabled and unpark them when it is reenabled. The smpboot thread infrastructure takes care of keeping the force parked threads in place even across cpu hotplug. Aside of that the code implements the park/unpark facility of smp hotplug threads on its own, which is even more pointless. We have functionality in the smpboot thread code to do so. Use the new thread management functions and get rid of the unholy mess. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194147.470370113@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Create new thread handling infrastructureThomas Gleixner2017-09-141-0/+75
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The lockup detector reconfiguration tears down all watchdog threads when the watchdog is disabled and sets them up again when its enabled. That's a pointless exercise. The watchdog threads are not consuming an insane amount of resources, so it's enough to set them up at init time and keep them in parked position when the watchdog is disabled and unpark them when it is reenabled. The smpboot thread infrastructure takes care of keeping the force parked threads in place even across cpu hotplug. Another horrible mechanism are the open coded park/unpark loops which are used for reconfiguration of the watchdog. The smpboot infrastructure allows exactly the same via smpboot_update_cpumask_thread_percpu(), which is cpu hotplug safe. Using that instead of the open coded loops allows to get rid of the hotplug locking mess in the watchdog code. Implement a clean infrastructure which allows to replace the open coded nonsense. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194147.377182587@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* smpboot/threads, watchdog/core: Avoid runtime allocationThomas Gleixner2017-09-141-16/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | smpboot_update_cpumask_threads_percpu() allocates a temporary cpumask at runtime. This is suboptimal because the call site needs more code size for proper error handling than a statically allocated temporary mask requires data size. Add static temporary cpumask. The function is globaly serialized, so no further protection required. Remove the half baken error handling in the watchdog code and get rid of the export as there are no in tree modular users of that function. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194147.297288838@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Split out cpumask write functionThomas Gleixner2017-09-141-19/+21
| | | | | | | | | | | | | | | | | | | Split the write part of the cpumask proc handler out into a separate helper to avoid deep indentation. This also reduces the patch complexity in the following cleanups. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194147.218075991@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Clean up the #ifdef mazeThomas Gleixner2017-09-141-20/+13
| | | | | | | | | | | | | | | | | | The #ifdef maze in this file is horrible, group stuff at least a bit so one can figure out what belongs to what. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194147.139629546@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Clean up stub functionsThomas Gleixner2017-09-141-46/+22
| | | | | | | | | | | | | | | | | | | | Having stub functions which take a full page is not helping the readablility of code. Condense them and move the doubled #ifdef variant into the SYSFS section. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194147.045545271@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Remove the park_in_progress obfuscationThomas Gleixner2017-09-141-20/+17
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit: b94f51183b06 ("kernel/watchdog: prevent false hardlockup on overloaded system") tries to fix the following issue: proc_write() set_sample_period() <--- New sample period becoms visible <----- Broken starts proc_watchdog_update() watchdog_enable_all_cpus() watchdog_hrtimer_fn() update_watchdog_all_cpus() restart_timer(sample_period) watchdog_park_threads() thread->park() disable_nmi() <----- Broken ends The reason why this is broken is that the update of the watchdog threshold becomes immediately effective and visible for the hrtimer function which uses that value to rearm the timer. But the NMI/perf side still uses the old value up to the point where it is disabled. If the rate has been lowered then the NMI can run fast enough to 'detect' a hard lockup because the timer has not fired due to the longer period. The patch 'fixed' this by adding a variable: proc_write() set_sample_period() <----- Broken starts proc_watchdog_update() watchdog_enable_all_cpus() watchdog_hrtimer_fn() update_watchdog_all_cpus() restart_timer(sample_period) watchdog_park_threads() park_in_progress = 1 <----- Broken ends nmi_watchdog() if (park_in_progress) return; The only effect of this variable was to make the window where the breakage can hit small enough that it was not longer observable in testing. From a correctness point of view it is a pointless bandaid which merily papers over the root cause: the unsychronized update of the variable. Looking deeper into the related code pathes unearthed similar problems in the watchdog_start()/stop() functions. watchdog_start() perf_nmi_event_start() hrtimer_start() watchdog_stop() hrtimer_cancel() perf_nmi_event_stop() In both cases the call order is wrong because if the tasks gets preempted or the VM gets scheduled out long enough after the first call, then there is a chance that the next NMI will see a stale hrtimer interrupt count and trigger a false positive hard lockup splat. Get rid of park_in_progress so the code can be gradually deobfuscated and pruned from several layers of duct tape papering over the root cause, which has been either ignored or not understood at all. Once this is removed the underlying problem will be fixed by rewriting the proc interface to do a proper synchronized update. Address the start/stop() ordering problem as well by reverting the call order, so this part is at least correct now. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1709052038270.2393@nanos Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/hardlockup/perf: Prevent CPU hotplug deadlockThomas Gleixner2017-09-141-0/+25
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The following deadlock is possible in the watchdog hotplug code: cpus_write_lock() ... takedown_cpu() smpboot_park_threads() smpboot_park_thread() kthread_park() ->park() := watchdog_disable() watchdog_nmi_disable() perf_event_release_kernel(); put_event() _free_event() ->destroy() := hw_perf_event_destroy() x86_release_hardware() release_ds_buffers() get_online_cpus() when a per cpu watchdog perf event is destroyed which drops the last reference to the PMU hardware. The cleanup code there invokes get_online_cpus() which instantly deadlocks because the hotplug percpu rwsem is write locked. To solve this add a deferring mechanism: cpus_write_lock() kthread_park() watchdog_nmi_disable(deferred) perf_event_disable(event); move_event_to_deferred(event); .... cpus_write_unlock() cleaup_deferred_events() perf_event_release_kernel() This is still properly serialized against concurrent hotplug via the cpu_add_remove_lock, which is held by the task which initiated the hotplug event. This is also used to handle event destruction when the watchdog threads are parked via other mechanisms than CPU hotplug. Analyzed-by: Peter Zijlstra <peterz@infradead.org> Reported-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194146.884469246@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/hardlockup/perf: Remove broken self disable on failureThomas Gleixner2017-09-141-15/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The self disabling feature is broken vs. CPU hotplug locking: CPU 0 CPU 1 cpus_write_lock(); cpu_up(1) wait_for_completion() .... unpark_watchdog() ->unpark() perf_event_create() <- fails watchdog_enable &= ~NMI_WATCHDOG; .... cpus_write_unlock(); CPU 2 cpus_write_lock() cpu_down(2) wait_for_completion() wakeup(watchdog); watchdog() if (!(watchdog_enable & NMI_WATCHDOG)) watchdog_nmi_disable() perf_event_disable() .... cpus_read_lock(); stop_smpboot_threads() park_watchdog(); wait_for_completion(watchdog->parked); Result: End of hotplug and instantaneous full lockup of the machine. There is a similar problem with disabling the watchdog via the user space interface as the sysctl function fiddles with watchdog_enable directly. It's very debatable whether this is required at all. If the watchdog works nicely on N CPUs and it fails to enable on the N + 1 CPU either during hotplug or because the user space interface disabled it via sysctl cpumask and then some perf user grabbed the counter which is then unavailable for the watchdog when the sysctl cpumask gets changed back. There is no real justification for this. One of the reasons WHY this is done is the utter stupidity of the init code of the perf NMI watchdog. Instead of checking upfront at boot whether PERF is available and functional at all, it just does this check at run time over and over when user space fiddles with the sysctl. That's broken beyond repair along with the idiotic error code dependent warn level printks and the even more silly printk rate limiting. If the init code checks whether perf works at boot time, then this mess can be more or less avoided completely. Perf does not come magically into life at runtime. Brain usage while coding is overrated. Remove the cruft and add a temporary safe guard which gets removed later. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194146.806708429@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Mark hardlockup_detector_disable() __initThomas Gleixner2017-09-141-1/+1
| | | | | | | | | | | | | | | | | | The function is only used by the KVM init code. Mark it __init to prevent creative abuse. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194146.727134632@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Rename watchdog_proc_mutexThomas Gleixner2017-09-141-8/+7
| | | | | | | | | | | | | | | | | | Following patches will use the mutex for other purposes as well. Rename it as it is not longer a proc specific thing. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194146.647714850@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Rework CPU hotplug lockingThomas Gleixner2017-09-141-6/+6
| | | | | | | | | | | | | | | | | | | | | The watchdog proc interface causes extensive recursive locking of the CPU hotplug percpu rwsem, which is deadlock prone. Replace the get/put_online_cpus() pairs with cpu_hotplug_disable()/enable() calls for now. Later patches will remove that requirement completely. Reported-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194146.568079057@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Remove broken suspend/resume interfacesThomas Gleixner2017-09-141-88/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | This interface has several issues: - It's causing recursive locking of the hotplug lock. - It's complete overkill to teardown all threads and then recreate them The same can be achieved with the simple hardlockup_detector_perf_stop / restart() interfaces. The abuse from the busy looping poweroff() loop of PARISC has been solved as well. Remove the cruft. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194146.487537732@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* watchdog/core: Provide interface to stop from poweroff()Thomas Gleixner2017-09-141-1/+13
| | | | | | | | | | | | | | | | | | | | | | | PARISC has a a busy looping power off routine. If the watchdog is enabled the watchdog timer will still fire, but the thread is not running, which causes the softlockup watchdog to trigger. Provide a interface which allows to turn the watchdog off. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Helge Deller <deller@gmx.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Cc: linux-parisc@vger.kernel.org Link: http://lkml.kernel.org/r/20170912194146.327343752@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
* kernel/watchdog: Prevent false positives with turbo modesThomas Gleixner2017-08-181-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The hardlockup detector on x86 uses a performance counter based on unhalted CPU cycles and a periodic hrtimer. The hrtimer period is about 2/5 of the performance counter period, so the hrtimer should fire 2-3 times before the performance counter NMI fires. The NMI code checks whether the hrtimer fired since the last invocation. If not, it assumess a hard lockup. The calculation of those periods is based on the nominal CPU frequency. Turbo modes increase the CPU clock frequency and therefore shorten the period of the perf/NMI watchdog. With extreme Turbo-modes (3x nominal frequency) the perf/NMI period is shorter than the hrtimer period which leads to false positives. A simple fix would be to shorten the hrtimer period, but that comes with the side effect of more frequent hrtimer and softlockup thread wakeups, which is not desired. Implement a low pass filter, which checks the perf/NMI period against kernel time. If the perf/NMI fires before 4/5 of the watchdog period has elapsed then the event is ignored and postponed to the next perf/NMI. That solves the problem and avoids the overhead of shorter hrtimer periods and more frequent softlockup thread wakeups. Fixes: 58687acba592 ("lockup_detector: Combine nmi_watchdog and softlockup detector") Reported-and-tested-by: Kan Liang <Kan.liang@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: dzickus@redhat.com Cc: prarit@redhat.com Cc: ak@linux.intel.com Cc: babu.moger@oracle.com Cc: peterz@infradead.org Cc: eranian@google.com Cc: acme@redhat.com Cc: stable@vger.kernel.org Cc: atomlin@redhat.com Cc: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1708150931310.1886@nanos
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