[Bugs] [Bug 1434274] BZ for some bugs found while going through synctask code

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1434274



--- Comment #15 from Worker Ant <bugzilla-bot at gluster.org> ---
COMMIT: https://review.gluster.org/16931 committed in master by Pranith Kumar
Karampuri (pkarampu at redhat.com) 
------
commit 0f98f5c8070904810252c6fc1df23747afa4b1d7
Author: Ravishankar N <ravishankar at redhat.com>
Date:   Tue Mar 21 11:02:32 2017 +0530

    syncop:  don't wake task in synctask_wake unless really needed

    Problem:

    In EC and AFR, we launch synctasks during self-heal.

    (i) These tasks usually stackwind a FOP to all its children and call
    synctask_yield() which does a swapcontext to synctask_switchto() and puts
the
    task in syncenv's waitq by calling __wait(task). This happends as long as
the
    FOP ckbs from all children haven't been received.

    (ii) For each FOP cbk, we call synctask_wake() which again does a
swapcontext
    to synctask_switchto() which now puts the task in syncenv's runq by calling
    __run(task). When the task runs and the conext switches back to the FOP
path,
    it puts the task in waitq because we haven't heard from all children as
    explained in (i).

    Thus we are unnecessarily using the swapcontext syscalls to just toggle
    the task back and forth between the waitq and runq.

    Fix:
    Store the stackwind count in new variable 'syncbarrier->waitfor' before
    winding the fop. In each cbk when we call synctask_wake(),  perform an
actual
    wake only if the cbk count == stackwind count.

    Change-Id: Id62d3b6ffed5a8c50f8b79267fb34e9470ba5ed5
    BUG: 1434274
    Signed-off-by: Ravishankar N <ravishankar at redhat.com>
    Signed-off-by: Ashish Pandey <aspandey at redhat.com>
    Reviewed-on: https://review.gluster.org/16931
    Smoke: Gluster Build System <jenkins at build.gluster.org>
    Reviewed-by: Niels de Vos <ndevos at redhat.com>
    NetBSD-regression: NetBSD Build System <jenkins at build.gluster.org>
    CentOS-regression: Gluster Build System <jenkins at build.gluster.org>
    Reviewed-by: Pranith Kumar Karampuri <pkarampu at redhat.com>

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