[Bug nptl/17326] New: endless loop in __reclaim_stacks

["ma.jiang at zte dot com.cn" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=17326

            Bug ID: 17326
           Summary: endless loop in __reclaim_stacks
           Product: glibc
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: ma.jiang at zte dot com.cn
                CC: drepper.fsp at gmail dot com

Created attachment 7766
  --> https://sourceware.org/bugzilla/attachment.cgi?id=7766&action=edit
my fix for the bug

Hi all,
After the fix mentioned in https://bugzilla.redhat.com/show_bug.cgi?id=477705,
I can still reproduce the bug on a dual-core armv7 board. 
As the Linux kernel only guarantee a per-page atomicity when doing fork, just
adding a atomic_write_barrier is not enough to protect the
stack_used/stack_cache lists. We need to stop threads which tried to modify the
lists when a thread is doing fork, only then the child process could get a
coherent list, and the __reclaim_stacks could do the right job.
In fork, we have already done such things for io locks(see _IO_list_lock
(),_IO_list_resetlock () and _IO_list_unlock () in __libc_fork). I belive we
should also add some similar codes to protect the stack_used/stack_cache lists.
I have made a patch(see the attachment),  is that ok for trunk?

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