BLCR 0.7.0 beta4 is now available

From: Paul H. Hargrove (PHHargrove_at_lbl_dot_gov)
Date: Wed May 21 2008 - 13:54:12 PDT

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    I am pleased to announce the availability of BLCR 0.7.0_beta4 from
    Both source tarball and SRPM are available.  The filenames and MD5
    checksums are:
       3e88928c3cf1dbbf565923576f93c573  blcr-0.7.0_b4.tar.gz
       c84d536345d695fd74bfb5d75a03e176  blcr-0.7.0_b4-1.src.rpm
    Relative to the eventual 0.7.0 release, this Beta is lacking only
    testing by a wide enough audience.
    This release includes fixes for many minor bugs (and one significant one)
    discovered in testing of the previous beta.  In the process of fixing
    those issues, support for Linux 2.6.25 kernels was added.  Some portions
    of the code base have changed significantly as a result of the fixes
    contained in this beta.  Therefore, if you have successfully tested any
    of the previous betas, you are strongly encouraged to retest this one to
    ensure no feature/behavior of importance to your environment has
    changed, and that no bug you reported has reappeared.
    Below is an excerpt from the NEWS file listing user-visible changes
    relative to the 0.6.x series.
    If you have reported a bug recently, especially if you've been told to
    expect a fix in 0.7.0, please try out this Beta release and let us know
    if your problem is fixed and especially if it is not.
    Relative to the 0.6.x release series, BLCR is using a new configure and
    build mechanism that should work correctly with Xen-enabled kernels and
    other kernels that were problematic in previous releases.  If you are
    unable to configure or build this beta on any system where 0.6.x built
    successfully, PLEASE let us know because the new configure/build
    mechanism might be at fault.
    You are receiving this either because you are on the checkpoint_at_lbl_dot_gov
    list, because you've recently sent email to the list (or me directly)
    asking about BLCR status, or because our Bugzilla shows your interests
    in a bug fixed in this beta.
    May 21, 2008
    Enhanced functionality and expanded-support release.
     - This release adds support for 2.6.25 kernels.
     - This release adds EXPERIMENTAL support for Xen-enabled kernels (both
       dom0 and domU).  In our testing so far it either works great or not
       at all, depending on the installation.  We have not yet identified
       what distinguishes the working systems from the broken ones, and
       would appreciate feedback on your success or failure using BLCR
       with Xen-enabled Linux kernels.
     - As previously announced, this release removes support for 2.4.x kernels
       with the current exception of the RH9 and RHEL kernels (and derivatives)
       that contain backported NPTL support.  These too may be removed in the
       not too distant future.
     - As previously announced, this release begins the removal of support for
       LinuxThreads.  If you are using LinuxThreads you may experience random
       failures in the BLCR testsuite and with your own multithreaded apps.
       New interest in using BLCR with non-GNU libc may lead to a return of
       LinuxThreads support.  Please contact us if you have interest it this.
     - This release adds the following features to the cr_checkpoint utility:
        + --quiet option to suppress output from cr_checkpoint
        + --noclobber option (don't disturb existing files)
        + Options for treatment of ptrace() child and parent processes:
        + Options to save/restore executables and libraries in context files:
       See the cr_checkpoint manpage for more details on each of these.
     - This release adds the following features to the cr_restart utility:
        + --quiet option to suppress output from cr_restart
          Previously there was no way to do so without also losing the output
          of the restarted process(es).
        + Add --run-on-* family of options to provide user-specified error
          handling hooks.  Previously there was no way to automatically/safely
          distinguish a failure of cr_restart from a non-zero exit from the
          restarted application.  This resolves bug 1974.
        + Add --relocate option to enable restart-time replacement of file and
          and directory paths saved in the context file.
       See the cr_restart manpage for more details on each of these.
     - This release adds the following feature to the cr_run utility:
        + --omit option to run a process with BLCR support such that the
          process (and its descendants) will be omitted from checkpoints.
     - This release makes the following libcr API additions/changes:
        + cr_forward_checkpoint() is fully tested and thus no longer labeled
          as "use at your own risk".  Its documentation in libcr.h is now
          complete as well.
        + cr_register_hook() is fully tested and thus no longer labeled
          as "use at your own risk".
        + As anticipated in previous releases, the error code returned from
          cr_poll_checkpoint() has CHANGED for the case of restarting from a
          checkpoint of oneself.  This may break existing code that will not
          be prepared for the new errno value.  However, the previous value
          of EINVAL could have masked actual invalid-argument errors.
          The alternative of returning 0 (success) was considered, but was
          discarded because it was deemed valuable to be able to reliably
          distinguish whether one was continuing or restarting from a
          checkpoint of oneself.
        + As alternatives to CR_ETEMPFAIL and CR_PERMFAIL, authors of BLCR
          callbacks can now specify the errno values to be returned to the
          checkpoint requester on a case-by-case basis.
        + cr_tryenter_cs() has been added as a non-blocking alternative to
          the cr_enter_cs() function.
        + Several functions that would previously respond to usage errors
          with an abort() or an undefined behavior now return -1 with one of
          two new values of errno:
           * CR_ENOINIT  - caller has not made the required call to cr_init()
           * CR_ENOTCB   - call is only valid from a checkpoint callback
        + The following functions are marked as deprecated:
           * cr_request()
           * cr_request_file()
           * cr_request_fd()
          They do not provide any mechanism to specify the checkpoint scope
          or to detect errors.  They are currently implemented as (awkward)
          wrappers around cr_request_checkpoint() and cr_poll_checkpoint().
          They are scheduled to be removed in 0.8.0.
       See the comments in include/libcr.h for API documentation.
     - This release introduces two "stub" libraries: libcr_run and libcr_omit.
       They differ from the "full" libcr library in that they contain only a
       BLCR signal handler and the initialization code to register it.  They
       do not include any of the entry points declared in libcr.h, and the
       handler code does not run any callbacks.
       The cr_run utility now uses these libraries in LD_PRELOAD variable,
       rather than the full used in previous releases.
       See the BLCR User's Guide for information on using these libs.
     - This release makes several additions to the BLCR test suite, including
       tests of most of the features new to this release and some motivated by
       bugs fixed in this release.  Many existing tests have been expanded to
       exercise additional corner cases.
     - This release makes the following changes to "configure" behavior:
        + The --with-linux= option now accepts a kernel revision (the output
          or "uname -r") as a value, causing configure and search for that
          revision in some standard locations.  This is intended to make it
          easier and less error prone to specify for which kernel to build.
          In most modern distributions, this single option will be sufficient
          to configure BLCR for any installed kernel.
        + Previously --with-linux= would be used to specify a kernel source
          directory, and if needed --with-linux-obj= could be given to help
          find the corresponding build directory.  With this release the
          role of --with-linux= as changed to be that of a build directory
          and the option --with-linux-src= is available if the sources can't
          be found automatically.
        + The configure-time probes of the kernel headers and configuration
          are now performed using the full CFLAGS/CPPFLAGS from the Linux
          kbuild infrastructure.  This ensures proper configuration with
          Xen-enabled kernels that prepend Xen-specific components to the
          include path.
        + At configure time one can set KCC to specify that the kernel
          modules are to be built with a different C compiler than the
          user-space components of BLCR.
     - On the ARM platform, the "good enough for LinuxThreads" implementation
       of atomic operations has been replaced with truly atomic ops based
       on the kernel-level support added for NPTL.
     - As a temporary work-around for bug 2251, BLCR will currently refuse
       to checkpoint processes with files on hugetlbfs mmap()ed with the
       MAP_PRIVATE flag.  This is to avoid potentially serious instability
       that may result if BLCR attempts to checkpoint such a process.
     - Fixes the following user-visible bugs and "issues"
        + 1974 - Make it possible to decide whether a restart succeeded
        + 2023 - ARM atomics need update
        + 2042 - not linked to libc
        + 2214 - close cri_live_count race
        + 2216 - Move post-restart signal delivery to post-callback
        + 2247 - BLCR assumes 64-bit gcc on 64-bit arch
        + 2248 - Separate CC and KCC
        + 2265 - CR_CHECKPOINT_OMIT generates 0 byte context file
        + 2266 - process doing CR_CHECKPOINT_TEMP_FAILURE is killed!
        + 2271 - cr_checkpoint --clobber fails to overwrite file
        + 2272 - cr_get_restart_info returns wrong src path
        + 2274 - Invalid (zero or huge) pids seen at restart time
        + Stronger validation of BLCR against proper kernel version
        + Validation of BLCR's kernel module versions against each other
        + Performance improvements from better memory management and
          from coalescing of background work.
        + Preserve error codes for I/O errors.  Previously any error
          from a read/write at kernel level was reported as EIO.  Now
          the original errors (such as ENOSPC) are preserved.
        + Several others found by internal testing or reported by email
          and fixed without assigning bug numbers.
     - The file contrib/blcr.magic contains the format description needed
       by the "file" utility to identify BLCR's context files.
    Paul H. Hargrove                          PHHargrove_at_lbl_dot_gov
    Future Technologies Group
    HPC Research Department                   Tel: +1-510-495-2352
    Lawrence Berkeley National Laboratory     Fax: +1-510-486-6900

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