[Bug nptl/21031] New: pthread_key_delete() race with thread finalization

["leo at yuriev dot ru" <sourceware-bugzilla at sourceware dot org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=21031

            Bug ID: 21031
           Summary: pthread_key_delete() race with thread finalization
           Product: glibc
           Version: 2.24
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: leo at yuriev dot ru
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

A race condition could occur between the pthread_key_delete() and the
__nptl_deallocate_tsd().

For instance, __nptl_deallocate_tsd() could call a destructor for the key,
immediately before the pthread_key_delete() invalidates it (from an another
thread), and will continue destructor execution after the completion of
pthread_key_delete().

>From a user code this looks as if the corresponding destructor executes after
the key has been removed by pthread_key_delete(), and there is no way to know
whether was destructor called/executed or not.

Suggest add pthread_rwlock_rdlock() for __nptl_deallocate_tsd() and
pthread_rwlock_wrlock() for pthread_key_delete().

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