[Bugs] [Bug 1740519] New: event: rename event_XXX with gf_ prefixed to avoid crash when apps linked libevent at the same time

bugzilla at redhat.com bugzilla at redhat.com
Tue Aug 13 08:15:51 UTC 2019


            Bug ID: 1740519
           Summary: event: rename event_XXX with gf_ prefixed to avoid
                    crash when apps linked libevent at the same time
           Product: GlusterFS
           Version: 7
            Status: NEW
         Component: eventsapi
          Assignee: bugs at gluster.org
          Reporter: xiubli at redhat.com
  Target Milestone: ---
    Classification: Community

Description of problem:

event: rename event_XXX with gf_ prefixed

I hit one crash issue when using the libgfapi.

In the libgfapi it will call glfs_poller() --> event_dispatch()
in file api/src/glfs.c:721, and the event_dispatch() is defined
by libgluster locally, the problem is the name of event_dispatch()
is the extremly the same with the one from libevent package form
the OS.

For example, if a executable program Foo, which will also use and
link the libevent and the libgfapi at the same time, I can hit the
crash, like:

kernel: glfs_glfspoll[68486]: segfault at 1c0 ip 00007fef006fd2b8 sp
00007feeeaffce30 error 4 in libevent-2.0.so.5.1.9[7fef006ed000+46000]

The link for Foo is:
lib_foo_LADD = -levent $(GFAPI_LIBS)
It will crash.

This is because the glfs_poller() is calling the event_dispatch() from
the libevent, not the libglsuter.

The gfapi link info :
GFAPI_LIBS = -lacl -lgfapi -lglusterfs -lgfrpc -lgfxdr -luuid

If I link Foo like:
lib_foo_LADD = $(GFAPI_LIBS) -levent
It will works well without any problem.

And if Foo call one private lib, such as handler_glfs.so, and the
handler_glfs.so will link the GFAPI_LIBS directly, while the Foo won't
and it will dlopen(handler_glfs.so), then the crash will be hit everytime.

The link info will be:
foo_LADD = -levent
libhandler_glfs_LIBADD = $(GFAPI_LIBS)

I can avoid the crash temporarily by linking the GFAPI_LIBS in Foo too like:
foo_LADD = $(GFAPI_LIBS) -levent
libhandler_glfs_LIBADD = $(GFAPI_LIBS)

But this is ugly since the Foo won't use any APIs from the GFAPI_LIBS.

And in some cases when the --as-needed link option is added(on many dists
it is added as default), then the crash is back again, the above workaround
won't work.

How reproducible:

Link libveent and libgfapi at the same time, then run the app.

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