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From: "xujing99 at huawei dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug admin/28331] New: Multi-threaded exec pthread_create and dlopen
 may cause deadlock
Date: Sat, 11 Sep 2021 10:35:42 +0000
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X-Bugzilla-Version: 2.35
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28331

            Bug ID: 28331
           Summary: Multi-threaded exec pthread_create and dlopen may
                    cause deadlock
           Product: glibc
           Version: 2.35
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: admin
          Assignee: unassigned at sourceware dot org
          Reporter: xujing99 at huawei dot com
                CC: carlos at redhat dot com
  Target Milestone: ---

after merge commit 1387ad6225c2222f027790e3f460e31aa5dd2c54, multi-threaded
exec pthread_create and dlopen may cause deadlock.

thread1=EF=BC=9Adlopen hold dl_load_lock and then load a dynamic library wh=
ich will
hold ACE_lock(defined by my self)
thread2=EF=BC=9Aa program hold ACE_lock and then call
pthread_create=3D>_dl_allocate_tls_init will hold dlopen dl_load_lock

in this case, it will cause deadlock.

for example:
thread1=EF=BC=9Adlopen =3D> hold dl_load_lock =3D> spawn_n =3D> wait for ho=
ld ACE_lock
thread2=EF=BC=9Aspawn_n =3D> hold ACE_lock =3D> pthread_create =3D> _dl_all=
ocate_tls_init =3D>
wait for hold dl_load_lock
(spawn_n is my own function)

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