1. 05 Sep, 2018 1 commit
  2. 02 Nov, 2017 1 commit
    • Greg Kroah-Hartman's avatar
      License cleanup: add SPDX GPL-2.0 license identifier to files with no license · b2441318
      Greg Kroah-Hartman authored
      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: 's avatarKate Stewart <kstewart@linuxfoundation.org>
      Reviewed-by: 's avatarPhilippe Ombredanne <pombredanne@nexb.com>
      Reviewed-by: 's avatarThomas Gleixner <tglx@linutronix.de>
      Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      b2441318
  3. 27 Oct, 2017 3 commits
  4. 04 Oct, 2017 5 commits
  5. 14 Sep, 2017 21 commits
    • Thomas Gleixner's avatar
      watchdog/hardlockup: Clean up hotplug locking mess · ab5fe3ff
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      ab5fe3ff
    • Thomas Gleixner's avatar
      watchdog/hardlockup/perf: Use new perf CPU enable mechanism · 146c9d0e
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      146c9d0e
    • Thomas Gleixner's avatar
      watchdog/hardlockup/perf: Implement init time detection of perf · a994a314
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      a994a314
    • Thomas Gleixner's avatar
      watchdog/core: Get rid of the racy update loop · 09154985
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      09154985
    • Thomas Gleixner's avatar
      watchdog/core, powerpc: Make watchdog_nmi_reconfigure() two stage · 6592ad2f
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      6592ad2f
    • Thomas Gleixner's avatar
      watchdog/sysctl: Clean up sysctl variable name space · 7feeb9cd
      Thomas Gleixner authored
      Reflect that these variables are user interface related and remove the
      whitespace damage in the sysctl table while at it.
      Signed-off-by: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      7feeb9cd
    • Thomas Gleixner's avatar
      watchdog/core: Further simplify sysctl handling · e8b62b2d
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      e8b62b2d
    • Thomas Gleixner's avatar
      watchdog/core: Get rid of the thread teardown/setup dance · d57108d4
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      d57108d4
    • Thomas Gleixner's avatar
      watchdog/core: Create new thread handling infrastructure · 2eb2527f
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      2eb2527f
    • Thomas Gleixner's avatar
      smpboot/threads, watchdog/core: Avoid runtime allocation · 0d85923c
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      0d85923c
    • Thomas Gleixner's avatar
      watchdog/core: Split out cpumask write function · 05ba3de7
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      05ba3de7
    • Thomas Gleixner's avatar
      watchdog/core: Clean up the #ifdef maze · 368a7e2c
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      368a7e2c
    • Thomas Gleixner's avatar
      watchdog/core: Clean up stub functions · 2b9d7f23
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      2b9d7f23
    • Thomas Gleixner's avatar
      watchdog/core: Remove the park_in_progress obfuscation · 01f0a027
      Thomas Gleixner authored
      Commit:
      
        b94f5118 ("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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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@nanosSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      01f0a027
    • Thomas Gleixner's avatar
      watchdog/hardlockup/perf: Prevent CPU hotplug deadlock · 941154bd
      Thomas Gleixner authored
      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: 's avatarPeter Zijlstra <peterz@infradead.org>
      Reported-by: 's avatarBorislav Petkov <bp@alien8.de>
      Signed-off-by: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      941154bd
    • Thomas Gleixner's avatar
      watchdog/hardlockup/perf: Remove broken self disable on failure · 20d853fd
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      20d853fd
    • Thomas Gleixner's avatar
      watchdog/core: Mark hardlockup_detector_disable() __init · 7a355820
      Thomas Gleixner authored
      The function is only used by the KVM init code. Mark it __init to prevent
      creative abuse.
      Signed-off-by: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      7a355820
    • Thomas Gleixner's avatar
      watchdog/core: Rename watchdog_proc_mutex · 946d1977
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      946d1977
    • Thomas Gleixner's avatar
      watchdog/core: Rework CPU hotplug locking · b7a34981
      Thomas Gleixner authored
      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: 's avatarBorislav Petkov <bp@alien8.de>
      Signed-off-by: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      b7a34981
    • Thomas Gleixner's avatar
      watchdog/core: Remove broken suspend/resume interfaces · 5490125d
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      5490125d
    • Thomas Gleixner's avatar
      watchdog/core: Provide interface to stop from poweroff() · 6554fd8c
      Thomas Gleixner authored
      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: 's avatarThomas Gleixner <tglx@linutronix.de>
      Reviewed-by: 's avatarDon 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.deSigned-off-by: 's avatarIngo Molnar <mingo@kernel.org>
      6554fd8c
  6. 18 Aug, 2017 1 commit
    • Thomas Gleixner's avatar
      kernel/watchdog: Prevent false positives with turbo modes · 7edaeb68
      Thomas Gleixner authored
      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: 58687acb ("lockup_detector: Combine nmi_watchdog and softlockup detector")
      Reported-and-tested-by: 's avatarKan Liang <Kan.liang@intel.com>
      Signed-off-by: 's avatarThomas 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
      7edaeb68
  7. 14 Jul, 2017 1 commit
  8. 12 Jul, 2017 2 commits
  9. 02 Mar, 2017 3 commits
  10. 25 Jan, 2017 1 commit
  11. 15 Dec, 2016 1 commit