1. 16 May, 2018 1 commit
    • Waiman Long's avatar
      locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED flag · d7d760ef
      Waiman Long authored
      There are use cases where a rwsem can be acquired by one task, but
      released by another task. In thess cases, optimistic spinning may need
      to be disabled.  One example will be the filesystem freeze/thaw code
      where the task that freezes the filesystem will acquire a write lock
      on a rwsem and then un-owns it before returning to userspace. Later on,
      another task will come along, acquire the ownership, thaw the filesystem
      and release the rwsem.
      Bit 0 of the owner field was used to designate that it is a reader
      owned rwsem. It is now repurposed to mean that the owner of the rwsem
      is not known. If only bit 0 is set, the rwsem is reader owned. If bit
      0 and other bits are set, it is writer owned with an unknown owner.
      One such value for the latter case is (-1L). So we can set owner to 1 for
      reader-owned, -1 for writer-owned. The owner is unknown in both cases.
      To handle transfer of rwsem ownership, the higher level code should
      set the owner field to -1 to indicate a write-locked rwsem with unknown
      owner.  Optimistic spinning will be disabled in this case.
      Once the higher level code figures who the new owner is, it can then
      set the owner field accordingly.
      Tested-by: Amir Goldstein's avatarAmir Goldstein <amir73il@gmail.com>
      Signed-off-by: Waiman Long's avatarWaiman Long <longman@redhat.com>
      Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Davidlohr Bueso <dave@stgolabs.net>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Matthew Wilcox <willy@infradead.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Theodore Y. Ts'o <tytso@mit.edu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Will Deacon <will.deacon@arm.com>
      Cc: linux-fsdevel@vger.kernel.org
      Link: http://lkml.kernel.org/r/1526420991-21213-2-git-send-email-longman@redhat.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
  2. 31 Mar, 2018 1 commit
  3. 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
      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: default avatarKate Stewart <kstewart@linuxfoundation.org>
      Reviewed-by: default avatarPhilippe Ombredanne <pombredanne@nexb.com>
      Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
  4. 10 Oct, 2017 1 commit
  5. 16 Mar, 2017 1 commit
  6. 02 Mar, 2017 1 commit
  7. 08 Jun, 2016 1 commit
    • Waiman Long's avatar
      locking/rwsem: Add reader-owned state to the owner field · 19c5d690
      Waiman Long authored
      Currently, it is not possible to determine for sure if a reader
      owns a rwsem by looking at the content of the rwsem data structure.
      This patch adds a new state RWSEM_READER_OWNED to the owner field
      to indicate that readers currently own the lock. This enables us to
      address the following 2 issues in the rwsem optimistic spinning code:
       1) rwsem_can_spin_on_owner() will disallow optimistic spinning if
          the owner field is NULL which can mean either the readers own
          the lock or the owning writer hasn't set the owner field yet.
          In the latter case, we miss the chance to do optimistic spinning.
       2) While a writer is waiting in the OSQ and a reader takes the lock,
          the writer will continue to spin when out of the OSQ in the main
          rwsem_optimistic_spin() loop as the owner field is NULL wasting
          CPU cycles if some of readers are sleeping.
      Adding the new state will allow optimistic spinning to go forward as
      long as the owner field is not RWSEM_READER_OWNED and the owner is
      running, if set, but stop immediately when that state has been reached.
      On a 4-socket Haswell machine running on a 4.6-rc1 based kernel, the
      fio test with multithreaded randrw and randwrite tests on the same
      file on a XFS partition on top of a NVDIMM were run, the aggregated
      bandwidths before and after the patch were as follows:
        Test      BW before patch     BW after patch  % change
        ----      ---------------     --------------  --------
        randrw         988 MB/s          1192 MB/s      +21%
        randwrite     1513 MB/s          1623 MB/s      +7.3%
      The perf profile of the rwsem_down_write_failed() function in randrw
      before and after the patch were:
         19.95%  5.88%  fio  [kernel.vmlinux]  [k] rwsem_down_write_failed
         14.20%  1.52%  fio  [kernel.vmlinux]  [k] rwsem_down_write_failed
      The actual CPU cycles spend in rwsem_down_write_failed() dropped from
      5.88% to 1.52% after the patch.
      The xfstests was also run and no regression was observed.
      Signed-off-by: default avatarWaiman Long <Waiman.Long@hpe.com>
      Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Acked-by: default avatarJason Low <jason.low2@hp.com>
      Acked-by: default avatarDavidlohr Bueso <dave@stgolabs.net>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Dave Chinner <david@fromorbit.com>
      Cc: Douglas Hatch <doug.hatch@hpe.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Peter Hurley <peter@hurleysoftware.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Scott J Norton <scott.norton@hpe.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/1463534783-38814-2-git-send-email-Waiman.Long@hpe.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
  8. 26 May, 2016 1 commit
  9. 22 Apr, 2016 1 commit
    • Michal Hocko's avatar
      locking/rwsem: Provide down_write_killable() · 916633a4
      Michal Hocko authored
      Now that all the architectures implement the necessary glue code
      we can introduce down_write_killable(). The only difference wrt. regular
      down_write() is that the slow path waits in TASK_KILLABLE state and the
      interruption by the fatal signal is reported as -EINTR to the caller.
      Signed-off-by: default avatarMichal Hocko <mhocko@suse.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Chris Zankel <chris@zankel.net>
      Cc: David S. Miller <davem@davemloft.net>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Max Filippov <jcmvbkbc@gmail.com>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
      Cc: Signed-off-by: Jason Low <jason.low2@hp.com>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Tony Luck <tony.luck@intel.com>
      Cc: linux-alpha@vger.kernel.org
      Cc: linux-arch@vger.kernel.org
      Cc: linux-ia64@vger.kernel.org
      Cc: linux-s390@vger.kernel.org
      Cc: linux-sh@vger.kernel.org
      Cc: linux-xtensa@linux-xtensa.org
      Cc: sparclinux@vger.kernel.org
      Link: http://lkml.kernel.org/r/1460041951-22347-12-git-send-email-mhocko@kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
  10. 18 Feb, 2015 1 commit
    • Davidlohr Bueso's avatar
      locking/rwsem: Set lock ownership ASAP · 7a215f89
      Davidlohr Bueso authored
      In order to optimize the spinning step, we need to set the lock
      owner as soon as the lock is acquired; after a successful counter
      cmpxchg operation, that is. This is particularly useful as rwsems
      need to set the owner to nil for readers, so there is a greater
      chance of falling out of the spinning. Currently we only set the
      owner much later in the game, in the more generic level -- latency
      can be specially bad when waiting for a node->next pointer when
      releasing the osq in up_write calls.
      As such, update the owner inside rwsem_try_write_lock (when the
      lock is obtained after blocking) and rwsem_try_write_lock_unqueued
      (when the lock is obtained while spinning). This requires creating
      a new internal rwsem.h header to share the owner related calls.
      Also cleanup some headers for mutex and rwsem.
      Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Signed-off-by: default avatarDavidlohr Bueso <dbueso@suse.de>
      Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Jason Low <jason.low2@hp.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Tim Chen <tim.c.chen@linux.intel.com>
      Link: http://lkml.kernel.org/r/1422609267-15102-4-git-send-email-dave@stgolabs.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
  11. 16 Jul, 2014 1 commit
  12. 05 Jun, 2014 1 commit
    • Davidlohr Bueso's avatar
      locking/rwsem: Support optimistic spinning · 4fc828e2
      Davidlohr Bueso authored
      We have reached the point where our mutexes are quite fine tuned
      for a number of situations. This includes the use of heuristics
      and optimistic spinning, based on MCS locking techniques.
      Exclusive ownership of read-write semaphores are, conceptually,
      just about the same as mutexes, making them close cousins. To
      this end we need to make them both perform similarly, and
      right now, rwsems are simply not up to it. This was discovered
      by both reverting commit 4fc3f1d6 (mm/rmap, migration: Make
      rmap_walk_anon() and try_to_unmap_anon() more scalable) and
      similarly, converting some other mutexes (ie: i_mmap_mutex) to
      rwsems. This creates a situation where users have to choose
      between a rwsem and mutex taking into account this important
      performance difference. Specifically, biggest difference between
      both locks is when we fail to acquire a mutex in the fastpath,
      optimistic spinning comes in to play and we can avoid a large
      amount of unnecessary sleeping and overhead of moving tasks in
      and out of wait queue. Rwsems do not have such logic.
      This patch, based on the work from Tim Chen and I, adds support
      for write-side optimistic spinning when the lock is contended.
      It also includes support for the recently added cancelable MCS
      locking for adaptive spinning. Note that is is only applicable
      to the xadd method, and the spinlock rwsem variant remains intact.
      Allowing optimistic spinning before putting the writer on the wait
      queue reduces wait queue contention and provided greater chance
      for the rwsem to get acquired. With these changes, rwsem is on par
      with mutex. The performance benefits can be seen on a number of
      workloads. For instance, on a 8 socket, 80 core 64bit Westmere box,
      aim7 shows the following improvements in throughput:
       |   Workload   | throughput-increase | number of users |
       | alltests     | 20%                 | >1000           |
       | custom       | 27%, 60%            | 10-100, >1000   |
       | high_systime | 36%, 30%            | >100, >1000     |
       | shared       | 58%, 29%            | 10-100, >1000   |
      There was also improvement on smaller systems, such as a quad-core
      x86-64 laptop running a 30Gb PostgreSQL (pgbench) workload for up
      to +60% in throughput for over 50 clients. Additionally, benefits
      were also noticed in exim (mail server) workloads. Furthermore, no
      performance regression have been seen at all.
      Based-on-work-from: Tim Chen <tim.c.chen@linux.intel.com>
      Signed-off-by: default avatarDavidlohr Bueso <davidlohr@hp.com>
      [peterz: rej fixup due to comment patches, sched/rt.h header]
      Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Cc: Alex Shi <alex.shi@linaro.org>
      Cc: Andi Kleen <andi@firstfloor.org>
      Cc: Michel Lespinasse <walken@google.com>
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Peter Hurley <peter@hurleysoftware.com>
      Cc: "Paul E.McKenney" <paulmck@linux.vnet.ibm.com>
      Cc: Jason Low <jason.low2@hp.com>
      Cc: Aswin Chandramouleeswaran <aswin@hp.com>
      Cc: Andrew Morton <akpm@linux-foundation.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: "Scott J Norton" <scott.norton@hp.com>
      Cc: Andrea Arcangeli <aarcange@redhat.com>
      Cc: Chris Mason <clm@fb.com>
      Cc: Josef Bacik <jbacik@fusionio.com>
      Link: http://lkml.kernel.org/r/1399055055.6275.15.camel@buesod1.americas.hpqcorp.netSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
  13. 06 Nov, 2013 1 commit
  14. 23 Mar, 2013 1 commit
  15. 11 Jan, 2013 1 commit
  16. 28 Mar, 2012 1 commit
  17. 31 Oct, 2011 1 commit
    • Paul Gortmaker's avatar
      kernel: Map most files to use export.h instead of module.h · 9984de1a
      Paul Gortmaker authored
      The changed files were only including linux/module.h for the
      EXPORT_SYMBOL infrastructure, and nothing else.  Revector them
      onto the isolated export header for faster compile times.
      Nothing to see here but a whole lot of instances of:
        -#include <linux/module.h>
        +#include <linux/export.h>
      This commit is only changing the kernel dir; next targets
      will probably be mm, fs, the arch dirs, etc.
      Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
  18. 26 Jul, 2011 1 commit
  19. 21 Jul, 2011 1 commit
  20. 18 Dec, 2007 1 commit
  21. 19 Jul, 2007 1 commit
  22. 08 May, 2007 1 commit
  23. 03 Jul, 2006 2 commits