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2018-08-30watchdog: Mark watchdog touch functions as notraceVincent Whitchurch1-1/+1
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
2018-08-03watchdog: Reduce message verbositySinan Kaya1-2/+2
Code is emitting the following error message during boot on systems without PMU hardware support while probing NMI capability. NMI watchdog: Perf event create on CPU 0 failed with -2 This error is emitted as the perf subsystem returns -ENOENT due to lack of PMUs in the system. It is followed by the warning that NMI watchdog is disabled: NMI watchdog: Perf NMI watchdog permanently disabled While NMI disabled information is useful for ordinary users, seeing a PERF event create failed with error code -2 is not. Reduce the message severity to debug so that if debugging is still possible in case the error code returned by perf is required for analysis. Signed-off-by: Sinan Kaya <okaya@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Don Zickus <dzickus@redhat.com> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Colin Ian King <colin.king@canonical.com> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=599368 Link: https://lkml.kernel.org/r/20180803060943.2643-1-okaya@kernel.org
2017-11-04Merge branch 'linus' into core/urgent, to pick up dependent commitsIngo Molnar1-0/+1
We want to fix an objtool build warning that got introduced in the latest upstream kernel. Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-11-02License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseGreg Kroah-Hartman1-0/+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>
2017-11-01watchdog/hardlockup/perf: Use atomics to track in-use cpu counterDon Zickus1-3/+5
Guenter reported: There is still a problem. When running echo 6 > /proc/sys/kernel/watchdog_thresh echo 5 > /proc/sys/kernel/watchdog_thresh repeatedly, the message NMI watchdog: Enabled. Permanently consumes one hw-PMU counter. stops after a while (after ~10-30 iterations, with fluctuations). Maybe watchdog_cpus needs to be atomic ? That's correct as this again is affected by the asynchronous nature of the smpboot thread unpark mechanism. CPU 0 CPU1 CPU2 write(watchdog_thresh, 6) stop() park() update() start() unpark() thread->unpark() cnt++; write(watchdog_thresh, 5) thread->unpark() stop() park() thread->park() cnt--; cnt++; update() start() unpark() That's not a functional problem, it just affects the informational message. Convert watchdog_cpus to atomic_t to prevent the problem Reported-and-tested-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Link: https://lkml.kernel.org/r/20171101181126.j727fqjmdthjz4xk@redhat.com
2017-11-01watchdog/harclockup/perf: Revert a33d44843d45 ("watchdog/hardlockup/perf: ↵Thomas Gleixner1-2/+5
Simplify deferred event destroy") Guenter reported a crash in the watchdog/perf code, which is caused by cleanup() and enable() running concurrently. The reason for this is: The watchdog functions are serialized via the watchdog_mutex and cpu hotplug locking, but the enable of the perf based watchdog happens in context of the unpark callback of the smpboot thread. But that unpark function is not synchronous inside the locking. The unparking of the thread just wakes it up and leaves so there is no guarantee when the thread is executing. If it starts running _before_ the cleanup happened then it will create a event and overwrite the dead event pointer. The new event is then cleaned up because the event is marked dead. lock(watchdog_mutex); lockup_detector_reconfigure(); cpus_read_lock(); stop(); park() update(); start(); unpark() cpus_read_unlock(); thread runs() overwrite dead event ptr cleanup(); free new event, which is active inside perf.... unlock(watchdog_mutex); The park side is safe as that actually waits for the thread to reach parked state. Commit a33d44843d45 removed the protection against this kind of scenario under the stupid assumption that the hotplug serialization and the watchdog_mutex cover everything. Bring it back. Reverts: a33d44843d45 ("watchdog/hardlockup/perf: Simplify deferred event destroy") Reported-and-tested-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Thomas Feels-stupid Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Don Zickus <dzickus@redhat.com> Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1710312145190.1942@nanos
2017-09-28watchdog/hardlockup/perf: Fix spelling mistake: "permanetely" -> "permanently"Colin Ian King1-1/+1
Trivial fix to spelling mistake in pr_info message Signed-off-by: Colin Ian King <colin.king@canonical.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Don Zickus <dzickus@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Babu Moger <babu.moger@oracle.com> Link: https://lkml.kernel.org/r/20170926093603.7756-1-colin.king@canonical.com
2017-09-25watchdog/hardlockup/perf: Cure UP damageThomas Gleixner1-1/+6
for_each_cpu() unintuitively reports CPU0 as set independend of the actual cpumask content on UP kernels. That leads to a NULL pointer dereference when the cleanup function is invoked and there is no event to clean up. Reported-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2017-09-14watchdog/hardlockup/perf: Simplify deferred event destroyThomas Gleixner1-5/+2
Now that all functionality is properly serialized against CPU hotplug, remove the extra per cpu storage which holds the disabled events for cleanup. The core makes sure that cleanup happens before new events are created. 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/20170912194148.340708074@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-14watchdog/hardlockup/perf: Use new perf CPU enable mechanismThomas Gleixner1-83/+5
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>
2017-09-14watchdog/hardlockup/perf: Implement CPU enable replacementThomas Gleixner1-0/+11
watchdog_nmi_enable() is an unparseable mess, Provide a clean perf specific implementation, which will be used when the existing setup/teardown mess is replaced. 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/20170912194148.180215498@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-14watchdog/hardlockup/perf: Implement init time perf validationThomas Gleixner1-0/+37
The watchdog tries to create perf events even after it figured out that perf is not functional or the requested event is not supported. That's braindead as this can be done once at init time and if not supported the NMI watchdog can be turned off unconditonally. Implement the perf hardlockup detector functionality for that. This creates a new event create function, which will replace the unholy mess of the existing one in later patches. 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/20170912194148.019090547@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-09-14watchdog/core: Remove the park_in_progress obfuscationThomas Gleixner1-5/+2
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>
2017-09-14watchdog/hardlockup/perf: Prevent CPU hotplug deadlockThomas Gleixner1-6/+28
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>
2017-09-14watchdog/hardlockup/perf: Remove broken self disable on failureThomas Gleixner1-13/+7
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>
2017-09-14watchdog/hardlockup: Provide interface to stop/restart perf eventsPeter Zijlstra1-0/+41
Provide an interface to stop and restart perf NMI watchdog events on all CPUs. This is only usable during init and especially for handling the perf HT bug on Intel machines. It's safe to use it this way as nothing can start/stop the NMI watchdog in parallel. Signed-off-by: Peter Zijlstra <peterz@infradead.org> 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: Sebastian Siewior <bigeasy@linutronix.de> Cc: Ulrich Obergfell <uobergfe@redhat.com> Link: http://lkml.kernel.org/r/20170912194146.167649596@linutronix.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-08-18kernel/watchdog: Prevent false positives with turbo modesThomas Gleixner1-0/+59
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
2017-07-13kernel/watchdog: split up config optionsNicholas Piggin1-32/+0
Split SOFTLOCKUP_DETECTOR from LOCKUP_DETECTOR, and split HARDLOCKUP_DETECTOR_PERF from HARDLOCKUP_DETECTOR. LOCKUP_DETECTOR implies the general boot, sysctl, and programming interfaces for the lockup detectors. An architecture that wants to use a hard lockup detector must define HAVE_HARDLOCKUP_DETECTOR_PERF or HAVE_HARDLOCKUP_DETECTOR_ARCH. Alternatively an arch can define HAVE_NMI_WATCHDOG, which provides the minimum arch_touch_nmi_watchdog, and it otherwise does its own thing and does not implement the LOCKUP_DETECTOR interfaces. sparc is unusual in that it has started to implement some of the interfaces, but not fully yet. It should probably be converted to a full HAVE_HARDLOCKUP_DETECTOR_ARCH. [npiggin@gmail.com: fix] Link: http://lkml.kernel.org/r/20170617223522.66c0ad88@roar.ozlabs.ibm.com Link: http://lkml.kernel.org/r/20170616065715.18390-4-npiggin@gmail.com Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Reviewed-by: Don Zickus <dzickus@redhat.com> Reviewed-by: Babu Moger <babu.moger@oracle.com> Tested-by: Babu Moger <babu.moger@oracle.com> [sparc] Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-13kernel/watchdog: introduce arch_touch_nmi_watchdog()Nicholas Piggin1-3/+2
For architectures that define HAVE_NMI_WATCHDOG, instead of having them provide the complete touch_nmi_watchdog() function, just have them provide arch_touch_nmi_watchdog(). This gives the generic code more flexibility in implementing this function, and arch implementations don't miss out on touching the softlockup watchdog or other generic details. Link: http://lkml.kernel.org/r/20170616065715.18390-3-npiggin@gmail.com Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Reviewed-by: Don Zickus <dzickus@redhat.com> Reviewed-by: Babu Moger <babu.moger@oracle.com> Tested-by: Babu Moger <babu.moger@oracle.com> [sparc] Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-03-02sched/headers: Prepare for new header dependencies before moving code to ↵Ingo Molnar1-0/+2
<linux/sched/debug.h> We are going to split <linux/sched/debug.h> out of <linux/sched.h>, which will have to be picked up from other headers and a couple of .c files. Create a trivial placeholder <linux/sched/debug.h> file that just maps to <linux/sched.h> to make this patch obviously correct and bisectable. Include the new header in the files that are going to need it. Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> 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>
2017-02-23kernel/watchdog.c: do not hardcode CPU 0 as the initial threadPrarit Bhargava1-10/+15
When CONFIG_BOOTPARAM_HOTPLUG_CPU0 is enabled, the socket containing the boot cpu can be replaced. During the hot add event, the message NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter. is output implying that the NMI watchdog was disabled at some point. This is not the case and the message has caused confusion for users of systems that support the removal of the boot cpu socket. The watchdog code is coded to assume that cpu 0 is always the first cpu to initialize the watchdog, and the last to stop its watchdog thread. That is not the case for initializing if cpu 0 has been removed and added. The removal case has never been correct because the smpboot code will remove the watchdog threads starting with the lowest cpu number. This patch adds watchdog_cpus to track the number of cpus with active NMI watchdog threads so that the first and last thread can be used to set and clear the value of firstcpu_err. firstcpu_err is set when the first watchdog thread is enabled, and cleared when the last watchdog thread is disabled. Link: http://lkml.kernel.org/r/1480425321-32296-1-git-send-email-prarit@redhat.com Signed-off-by: Prarit Bhargava <prarit@redhat.com> Acked-by: Don Zickus <dzickus@redhat.com> Cc: Borislav Petkov <bp@suse.de> Cc: Tejun Heo <tj@kernel.org> Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Andi Kleen <ak@linux.intel.com> Cc: Joshua Hunt <johunt@akamai.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Babu Moger <babu.moger@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-01-25kernel/watchdog: prevent false hardlockup on overloaded systemDon Zickus1-0/+3
On an overloaded system, it is possible that a change in the watchdog threshold can be delayed long enough to trigger a false positive. This can easily be achieved by having a cpu spinning indefinitely on a task, while another cpu updates watchdog threshold. What happens is while trying to park the watchdog threads, the hrtimers on the other cpus trigger and reprogram themselves with the new slower watchdog threshold. Meanwhile, the nmi watchdog is still programmed with the old faster threshold. Because the one cpu is blocked, it prevents the thread parking on the other cpus from completing, which is needed to shutdown the nmi watchdog and reprogram it correctly. As a result, a false positive from the nmi watchdog is reported. Fix this by setting a park_in_progress flag to block all lockups until the parking is complete. Fix provided by Ulrich Obergfell. [akpm@linux-foundation.org: s/park_in_progress/watchdog_park_in_progress/] Link: http://lkml.kernel.org/r/1481041033-192236-1-git-send-email-dzickus@redhat.com Signed-off-by: Don Zickus <dzickus@redhat.com> Reviewed-by: Aaron Tomlin <atomlin@redhat.com> Cc: Ulrich Obergfell <uobergfe@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-12-15kernel/watchdog.c: move hardlockup detector to separate fileBabu Moger1-0/+227
Separate hardlockup code from watchdog.c and move it to watchdog_hld.c. It is mostly straight forward. Remove everything inside CONFIG_HARDLOCKUP_DETECTORS. This code will go to file watchdog_hld.c. Also update the makefile accordigly. Link: http://lkml.kernel.org/r/1478034826-43888-3-git-send-email-babu.moger@oracle.com Signed-off-by: Babu Moger <babu.moger@oracle.com> Acked-by: Don Zickus <dzickus@redhat.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Jiri Kosina <jkosina@suse.cz> Cc: Andi Kleen <andi@firstfloor.org> Cc: Yaowei Bai <baiyaowei@cmss.chinamobile.com> Cc: Aaron Tomlin <atomlin@redhat.com> Cc: Ulrich Obergfell <uobergfe@redhat.com> Cc: Tejun Heo <tj@kernel.org> Cc: Hidehiro Kawai <hidehiro.kawai.ez@hitachi.com> Cc: Josh Hunt <johunt@akamai.com> Cc: "David S. Miller" <davem@davemloft.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>