1. 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>
  2. 04 Aug, 2017 1 commit
    • Rafael J. Wysocki's avatar
      ACPI / PM: Prefer suspend-to-idle over S3 on some systems · e870c6c8
      Rafael J. Wysocki authored
      Modify the ACPI system sleep support setup code to select
      suspend-to-idle as the default system sleep state if
      (1) the ACPI_FADT_LOW_POWER_S0 flag is set in the FADT and
      (2) the Low Power Idle S0 _DSM interface has been discovered and
      (3) the default sleep state was not selected from the kernel command
      The main motivation for this change is that systems where the (1) and
      (2) conditions are met typically ship with OSes that don't exercise
      the S3 path in the platform firmware which remains untested and turns
      out to be non-functional at least in some cases.
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      Tested-by: default avatarMario Limonciello <mario.limonciello@dell.com>
  3. 24 Jul, 2017 2 commits
  4. 07 Feb, 2017 1 commit
  5. 21 Nov, 2016 1 commit
    • Rafael J. Wysocki's avatar
      PM / sleep: System sleep state selection interface rework · 406e7938
      Rafael J. Wysocki authored
      There are systems in which the platform doesn't support any special
      sleep states, so suspend-to-idle (PM_SUSPEND_FREEZE) is the only
      available system sleep state.  However, some user space frameworks
      only use the "mem" and (sometimes) "standby" sleep state labels, so
      the users of those systems need to modify user space in order to be
      able to use system suspend at all and that may be a pain in practice.
      Commit 0399d4db (PM / sleep: Introduce command line argument for
      sleep state enumeration) attempted to address this problem by adding
      a command line argument to change the meaning of the "mem" string in
      /sys/power/state to make it trigger suspend-to-idle (instead of
      However, there also are systems in which the platform does support
      special sleep states, but suspend-to-idle is the preferred one anyway
      (it even may save more energy than the platform-provided sleep states
      in some cases) and the above commit doesn't help in those cases.
      For this reason, rework the system sleep state selection interface
      again (but preserve backwards compatibiliby).  Namely, add a new
      sysfs file, /sys/power/mem_sleep, that will control the system
      suspend mode triggered by writing "mem" to /sys/power/state (in
      analogy with what /sys/power/disk does for hibernation).  Make it
      select suspend-to-RAM ("deep" sleep) by default (if supported) and
      fall back to suspend-to-idle ("s2idle") otherwise and add a new
      command line argument, mem_sleep_default, allowing that default to
      be overridden if need be.
      At the same time, drop the relative_sleep_states command line
      argument that doesn't make sense any more.
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      Tested-by: default avatarMario Limonciello <mario.limonciello@dell.com>
  6. 13 Sep, 2016 1 commit
  7. 15 Jul, 2016 1 commit
    • Rafael J. Wysocki's avatar
      x86 / hibernate: Use hlt_play_dead() when resuming from hibernation · 406f992e
      Rafael J. Wysocki authored
      On Intel hardware, native_play_dead() uses mwait_play_dead() by
      default and only falls back to the other methods if that fails.
      That also happens during resume from hibernation, when the restore
      (boot) kernel runs disable_nonboot_cpus() to take all of the CPUs
      except for the boot one offline.
      However, that is problematic, because the address passed to
      __monitor() in mwait_play_dead() is likely to be written to in the
      last phase of hibernate image restoration and that causes the "dead"
      CPU to start executing instructions again.  Unfortunately, the page
      containing the address in that CPU's instruction pointer may not be
      valid any more at that point.
      First, that page may have been overwritten with image kernel memory
      contents already, so the instructions the CPU attempts to execute may
      simply be invalid.  Second, the page tables previously used by that
      CPU may have been overwritten by image kernel memory contents, so the
      address in its instruction pointer is impossible to resolve then.
      A report from Varun Koyyalagunta and investigation carried out by
      Chen Yu show that the latter sometimes happens in practice.
      To prevent it from happening, temporarily change the smp_ops.play_dead
      pointer during resume from hibernation so that it points to a special
      "play dead" routine which uses hlt_play_dead() and avoids the
      inadvertent "revivals" of "dead" CPUs this way.
      A slightly unpleasant consequence of this change is that if the
      system is hibernated with one or more CPUs offline, it will generally
      draw more power after resume than it did before hibernation, because
      the physical state entered by CPUs via hlt_play_dead() is higher-power
      than the mwait_play_dead() one in the majority of cases.  It is
      possible to work around this, but it is unclear how much of a problem
      that's going to be in practice, so the workaround will be implemented
      later if it turns out to be necessary.
      Link: https://bugzilla.kernel.org/show_bug.cgi?id=106371Reported-by: default avatarVarun Koyyalagunta <cpudebug@centtech.com>
      Original-by: default avatarChen Yu <yu.c.chen@intel.com>
      Tested-by: default avatarChen Yu <yu.c.chen@intel.com>
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
      Acked-by: default avatarIngo Molnar <mingo@kernel.org>
  8. 10 Jul, 2016 1 commit
    • Rafael J. Wysocki's avatar
      PM / hibernate: Image data protection during restoration · 4c0b6c10
      Rafael J. Wysocki authored
      Make it possible to protect all pages holding image data during
      hibernate image restoration by setting them read-only (so as to
      catch attempts to write to those pages after image data have been
      stored in them).
      This adds overhead to image restoration code (it may cause large
      page mappings to be split as a result of page flags changes) and
      the errors it protects against should never happen in theory, so
      the feature is only active after passing hibernate=protect_image
      to the command line of the restore kernel.
      Also it only is built if CONFIG_DEBUG_RODATA is set.
      Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
  9. 27 Jun, 2016 1 commit
  10. 04 Jan, 2016 1 commit
  11. 19 May, 2015 1 commit
  12. 03 Nov, 2014 1 commit
  13. 02 Sep, 2014 1 commit
  14. 21 Jul, 2014 1 commit
  15. 26 May, 2014 2 commits
  16. 07 Apr, 2014 1 commit
  17. 01 Mar, 2014 1 commit
  18. 01 Jul, 2012 1 commit
  19. 01 May, 2012 2 commits
    • Rafael J. Wysocki's avatar
      PM / Sleep: Add user space interface for manipulating wakeup sources, v3 · b86ff982
      Rafael J. Wysocki authored
      Android allows user space to manipulate wakelocks using two
      sysfs file located in /sys/power/, wake_lock and wake_unlock.
      Writing a wakelock name and optionally a timeout to the wake_lock
      file causes the wakelock whose name was written to be acquired (it
      is created before is necessary), optionally with the given timeout.
      Writing the name of a wakelock to wake_unlock causes that wakelock
      to be released.
      Implement an analogous interface for user space using wakeup sources.
      Add the /sys/power/wake_lock and /sys/power/wake_unlock files
      allowing user space to create, activate and deactivate wakeup
      sources, such that writing a name and optionally a timeout to
      wake_lock causes the wakeup source of that name to be activated,
      optionally with the given timeout.  If that wakeup source doesn't
      exist, it will be created and then activated.  Writing a name to
      wake_unlock causes the wakeup source of that name, if there is one,
      to be deactivated.  Wakeup sources created with the help of
      wake_lock that haven't been used for more than 5 minutes are garbage
      collected and destroyed.  Moreover, there can be only WL_NUMBER_LIMIT
      wakeup sources created with the help of wake_lock present at a time.
      The data type used to track wakeup sources created by user space is
      called "struct wakelock" to indicate the origins of this feature.
      This version of the patch includes an rbtree manipulation fix from John Stultz.
      Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
      Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      Reviewed-by: default avatarNeilBrown <neilb@suse.de>
    • Rafael J. Wysocki's avatar
      PM / Sleep: Implement opportunistic sleep, v2 · 7483b4a4
      Rafael J. Wysocki authored
      Introduce a mechanism by which the kernel can trigger global
      transitions to a sleep state chosen by user space if there are no
      active wakeup sources.
      It consists of a new sysfs attribute, /sys/power/autosleep, that
      can be written one of the strings returned by reads from
      /sys/power/state, an ordered workqueue and a work item carrying out
      the "suspend" operations.  If a string representing the system's
      sleep state is written to /sys/power/autosleep, the work item
      triggering transitions to that state is queued up and it requeues
      itself after every execution until user space writes "off" to
      That work item enables the detection of wakeup events using the
      functions already defined in drivers/base/power/wakeup.c (with one
      small modification) and calls either pm_suspend(), or hibernate() to
      put the system into a sleep state.  If a wakeup event is reported
      while the transition is in progress, it will abort the transition and
      the "system suspend" work item will be queued up again.
      Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
      Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      Reviewed-by: default avatarNeilBrown <neilb@suse.de>
  20. 17 Feb, 2012 1 commit
  21. 13 Feb, 2012 1 commit
  22. 04 Feb, 2012 1 commit
    • Srivatsa S. Bhat's avatar
      PM / Freezer: Thaw only kernel threads if freezing of kernel threads fails · 379e0be8
      Srivatsa S. Bhat authored
      If freezing of kernel threads fails, we are expected to automatically
      thaw tasks in the error recovery path. However, at times, we encounter
      situations in which we would like the automatic error recovery path
      to thaw only the kernel threads, because we want to be able to do
      some more cleanup before we thaw userspace. Something like:
      error = freeze_kernel_threads();
      if (error) {
      	/* Do some cleanup */
      	/* Only then thaw userspace tasks*/
      An example of such a situation is where we freeze/thaw filesystems
      during suspend/hibernation. There, if freezing of kernel threads
      fails, we would like to thaw the frozen filesystems before thawing
      the userspace tasks.
      So, modify freeze_kernel_threads() to thaw only kernel threads in
      case of freezing failure. And change suspend_freeze_processes()
      accordingly. (At the same time, let us also get rid of the rather
      cryptic usage of the conditional operator (:?) in that function.)
      [rjw: In fact, this patch fixes a regression introduced during the
       3.3 merge window, because without it thaw_processes() may be called
       before swsusp_free() in some situations and that may lead to massive
       memory allocation failures.]
      Signed-off-by: default avatarSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
      Acked-by: default avatarTejun Heo <tj@kernel.org>
      Acked-by: default avatarNigel Cunningham <nigel@tuxonice.net>
      Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
  23. 06 Dec, 2011 1 commit
    • Srivatsa S. Bhat's avatar
      PM / Hibernate: Thaw processes in SNAPSHOT_CREATE_IMAGE ioctl test path · 97819a26
      Srivatsa S. Bhat authored
      Commit 2aede851 (PM / Hibernate: Freeze
      kernel threads after preallocating memory) moved the freezing of kernel
      threads to hibernation_snapshot() function.
      So now, if the call to hibernation_snapshot() returns early due to a
      successful hibernation test, the caller has to thaw processes to ensure
      that the system gets back to its original state.
      But in SNAPSHOT_CREATE_IMAGE hibernation ioctl, the caller does not thaw
      processes in case hibernation_snapshot() returned due to a successful
      freezer test. Fix this issue. But note we still send the value of 'in_suspend'
      (which is now 0) to userspace, because we are not in an error path per-se,
      and moreover, the value of in_suspend correctly depicts the situation here.
      Signed-off-by: default avatarSrivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
      Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
  24. 16 Oct, 2011 2 commits
    • Bojan Smojver's avatar
      PM / Hibernate: Improve performance of LZO/plain hibernation, checksum image · 081a9d04
      Bojan Smojver authored
      Use threads for LZO compression/decompression on hibernate/thaw.
      Improve buffering on hibernate/thaw.
      Calculate/verify CRC32 of the image pages on hibernate/thaw.
      In my testing, this improved write/read speed by a factor of about two.
      Signed-off-by: default avatarBojan Smojver <bojan@rexursive.com>
      Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
    • Rafael J. Wysocki's avatar
      PM / Hibernate: Freeze kernel threads after preallocating memory · 2aede851
      Rafael J. Wysocki authored
      There is a problem with the current ordering of hibernate code which
      leads to deadlocks in some filesystems' memory shrinkers.  Namely,
      some filesystems use freezable kernel threads that are inactive when
      the hibernate memory preallocation is carried out.  Those same
      filesystems use memory shrinkers that may be triggered by the
      hibernate memory preallocation.  If those memory shrinkers wait for
      the frozen kernel threads, the hibernate process deadlocks (this
      happens with XFS, for one example).
      Apparently, it is not technically viable to redesign the filesystems
      in question to avoid the situation described above, so the only
      possible solution of this issue is to defer the freezing of kernel
      threads until the hibernate memory preallocation is done, which is
      implemented by this change.
      Unfortunately, this requires the memory preallocation to be done
      before the "prepare" stage of device freeze, so after this change the
      only way drivers can allocate additional memory for their freeze
      routines in a clean way is to use PM notifiers.
      Reported-by: default avatarChristoph <cr2005@u-club.de>
      Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
  25. 17 May, 2011 1 commit
    • Rafael J. Wysocki's avatar
      PM / Hibernate: Add sysfs knob to control size of memory for drivers · ddeb6487
      Rafael J. Wysocki authored
      Martin reports that on his system hibernation occasionally fails due
      to the lack of memory, because the radeon driver apparently allocates
      too much of it during the device freeze stage.  It turns out that the
      amount of memory allocated by radeon during hibernation (and
      presumably during system suspend too) depends on the utilization of
      the GPU (e.g. hibernating while there are two KDE 4 sessions with
      compositing enabled causes radeon to allocate more memory than for
      one KDE 4 session).
      In principle it should be possible to use image_size to make the
      memory preallocation mechanism free enough memory for the radeon
      driver, but in practice it is not easy to guess the right value
      because of the way the preallocation code uses image_size.  For this
      reason, it seems reasonable to allow users to control the amount of
      memory reserved for driver allocations made after the hibernate
      preallocation, which currently is constant and amounts to 1 MB.
      Introduce a new sysfs file, /sys/power/reserved_size, whose value
      will be used as the amount of memory to reserve for the
      post-preallocation reservations made by device drivers, in bytes.
      For backwards compatibility, set its default (and initial) value to
      the currently used number (1 MB).
      References: https://bugzilla.kernel.org/show_bug.cgi?id=34102Reported-and-tested-by: default avatarMartin Steigerwald <Martin@Lichtvoll.de>
      Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
  26. 16 Oct, 2010 2 commits
  27. 10 May, 2010 2 commits
  28. 14 Sep, 2009 1 commit
    • Rafael J. Wysocki's avatar
      PM/Hibernate: Do not release preallocated memory unnecessarily (rev. 2) · 64a473cb
      Rafael J. Wysocki authored
      Since the hibernation code is now going to use allocations of memory
      to make enough room for the image, it can also use the page frames
      allocated at this stage as image page frames.  The low-level
      hibernation code needs to be rearranged for this purpose, but it
      allows us to avoid freeing a great number of pages and allocating
      these same pages once again later, so it generally is worth doing.
      [rev. 2: Take highmem into account correctly.]
      Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
  29. 12 Jun, 2009 3 commits
  30. 21 Oct, 2008 1 commit
  31. 26 Jul, 2008 1 commit
    • Huang Ying's avatar
      kexec jump: save/restore device state · 89081d17
      Huang Ying authored
      This patch implements devices state save/restore before after kexec.
      This patch together with features in kexec_jump patch can be used for
      - A simple hibernation implementation without ACPI support.  You can kexec a
        hibernating kernel, save the memory image of original system and shutdown
        the system.  When resuming, you restore the memory image of original system
        via ordinary kexec load then jump back.
      - Kernel/system debug through making system snapshot.  You can make system
        snapshot, jump back, do some thing and make another system snapshot.
      - Cooperative multi-kernel/system.  With kexec jump, you can switch between
        several kernels/systems quickly without boot process except the first time.
        This appears like swap a whole kernel/system out/in.
      - A general method to call program in physical mode (paging turning
        off). This can be used to invoke BIOS code under Linux.
      The following user-space tools can be used with kexec jump:
      - kexec-tools needs to be patched to support kexec jump. The patches
        and the precompiled kexec can be download from the following URL:
             source: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec-tools-src_git_kh10.tar.bz2
             patches: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec-tools-patches_git_kh10.tar.bz2
             binary: http://khibernation.sourceforge.net/download/release_v10/kexec-tools/kexec_git_kh10
      - makedumpfile with patches are used as memory image saving tool, it
        can exclude free pages from original kernel memory image file. The
        patches and the precompiled makedumpfile can be download from the
        following URL:
             source: http://khibernation.sourceforge.net/download/release_v10/makedumpfile/makedumpfile-src_cvs_kh10.tar.bz2
             patches: http://khibernation.sourceforge.net/download/release_v10/makedumpfile/makedumpfile-patches_cvs_kh10.tar.bz2
             binary: http://khibernation.sourceforge.net/download/release_v10/makedumpfile/makedumpfile_cvs_kh10
      - An initramfs image can be used as the root file system of kexeced
        kernel. An initramfs image built with "BuildRoot" can be downloaded
        from the following URL:
             initramfs image: http://khibernation.sourceforge.net/download/release_v10/initramfs/rootfs_cvs_kh10.gz
        All user space tools above are included in the initramfs image.
      Usage example of simple hibernation:
      1. Compile and install patched kernel with following options selected:
      2. Build an initramfs image contains kexec-tool and makedumpfile, or
         download the pre-built initramfs image, called rootfs.gz in
         following text.
      3. Prepare a partition to save memory image of original kernel, called
         hibernating partition in following text.
      4. Boot kernel compiled in step 1 (kernel A).
      5. In the kernel A, load kernel compiled in step 1 (kernel B) with
         /sbin/kexec. The shell command line can be as follow:
         /sbin/kexec --load-preserve-context /boot/bzImage --mem-min=0x100000
           --mem-max=0xffffff --initrd=rootfs.gz
      6. Boot the kernel B with following shell command line:
         /sbin/kexec -e
      7. The kernel B will boot as normal kexec. In kernel B the memory
         image of kernel A can be saved into hibernating partition as
         jump_back_entry=`cat /proc/cmdline | tr ' ' '\n' | grep kexec_jump_back_entry | cut -d '='`
         echo $jump_back_entry > kexec_jump_back_entry
         cp /proc/vmcore dump.elf
         Then you can shutdown the machine as normal.
      8. Boot kernel compiled in step 1 (kernel C). Use the rootfs.gz as
         root file system.
      9. In kernel C, load the memory image of kernel A as follow:
         /sbin/kexec -l --args-none --entry=`cat kexec_jump_back_entry` dump.elf
      10. Jump back to the kernel A as follow:
         /sbin/kexec -e
         Then, kernel A is resumed.
      Implementation point:
      To support jumping between two kernels, before jumping to (executing)
      the new kernel and jumping back to the original kernel, the devices
      are put into quiescent state, and the state of devices and CPU is
      saved. After jumping back from kexeced kernel and jumping to the new
      kernel, the state of devices and CPU are restored accordingly. The
      devices/CPU state save/restore code of software suspend is called to
      implement corresponding function.
      Known issues:
      - Because the segment number supported by sys_kexec_load is limited,
        hibernation image with many segments may not be load. This is
        planned to be eliminated by adding a new flag to sys_kexec_load to
        make a image can be loaded with multiple sys_kexec_load invoking.
      Now, only the i386 architecture is supported.
      Signed-off-by: default avatarHuang Ying <ying.huang@intel.com>
      Acked-by: default avatarVivek Goyal <vgoyal@redhat.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Pavel Machek <pavel@ucw.cz>
      Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
      Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
  32. 01 Feb, 2008 1 commit