Re: Regression caused to gfapi applications with enabling client-io-threads by default

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On 10/06/2016 11:36 AM, Soumya Koduri wrote:


On 10/05/2016 07:32 PM, Pranith Kumar Karampuri wrote:


On Wed, Oct 5, 2016 at 2:00 PM, Soumya Koduri <skoduri@xxxxxxxxxx
<mailto:skoduri@xxxxxxxxxx>> wrote:

    Hi,

    With http://review.gluster.org/#/c/15051/
    <http://review.gluster.org/#/c/15051/>, performace/client-io-threads
    is enabled by default. But with that we see regression caused to
    nfs-ganesha application trying to un/re-export any glusterfs volume.
    This shall be the same case with any gfapi application using
    glfs_fini().

    More details and the RCA can be found at [1].

    In short, iot-worker threads spawned  (when the above option is
    enabled) are not cleaned up as part of io-threads-xlator->fini() and
    those threads could end up accessing invalid/freed memory post
    glfs_fini().

    The actual fix is to address io-threads-xlator->fini() to cleanup
    those threads before exiting. But since those threads' IDs are
    currently not stored, the fix could be very intricate and take a
    while. So till then to avoid all existing applications crash, I
    suggest to keep this option disabled by default and update this
    known_issue with enabling this option in the release-notes.

    I sent a patch to revert the commit -
    http://review.gluster.org/#/c/15616/
    <http://review.gluster.org/#/c/15616/> [2]


Good catch! I think the correct fix would be to make sure all threads
die as part of PARENT_DOWN then?

From my understanding, I think these threads should be cleaned up as part of xlator->fini().I am not sure if it needs to be handled even for PARENT_DOWN as well. Do we re-spawn the threads as part of PARENT_UP then?

Till that part gets fixed, can we make this option back to off by default to avoid the regressions with master and release-3.9 branch?
I agree with Soumya to make this option back to off until we get full fix as we are hitting regressions with Samba/ganesha both.

Thanks,
Soumya



    Comments/Suggestions are welcome.

    Thanks,
    Soumya

    [1] https://bugzilla.redhat.com/show_bug.cgi?id=1380619#c11
<https://bugzilla.redhat.com/show_bug.cgi?id=1380619#c11>
    [2] http://review.gluster.org/#/c/15616/
    <http://review.gluster.org/#/c/15616/>




--
Pranith
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