[Bugs] [Bug 1521213] New: crash when gifs_set_logging is called concurrently

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1521213

            Bug ID: 1521213
           Summary: crash when gifs_set_logging is called concurrently
           Product: GlusterFS
           Version: mainline
         Component: libgfapi
          Assignee: bugs at gluster.org
          Reporter: zhhuan at gmail.com
        QA Contact: bugs at gluster.org
                CC: bugs at gluster.org



Description of problem:
run fio to perform test in thread mode will cause gfapi to crash.

Digging into this issue, and found that glfs_set_logging changes THIS->ctx
without lock, during initialization "THIS" is actually global_xlator.
Concurrently changing it could result in global_xlator.ctx be changed to some
fs->ctx. Consider the following sequence.

thread1                    thread2
old_ctx = THIS->ctx                             // current old_ctx is
global_xlator.ctx
THIS->ctx = fs1->ctx
                           old_ctx = THIS->ctx  // it is fs1->ctx actually
                           THIS->ctx = fs2->ctx
THIS->ctx = old_ctx                             // revert back to
global_xlator.ctx
                           THIS->ctx = old_ctx  // THIS->ctx becomes fs1->ctx

global_xlator.ctx might refers to an invalid pointer and that causes subsequent
new fs init crash as they might use global_xlator.


Version-Release number of selected component (if applicable):


How reproducible:
run fio 

Steps to Reproduce:
1.
2.
3.

Actual results:


Expected results:


Additional info:

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