um: WARNING: at kernel/futex.c:786 __unqueue_futex

[richard -rw- weinberger]

Lai,

Your commit 2e12978a
(futex,plist: Pass the real head of the priority list to plist_del())
triggers gazillions warnings on User Mode Linux (x86, Linus' tree as of today):

------------[ cut here ]------------
WARNING: at kernel/futex.c:786 __unqueue_futex+0x12/0x16()
Modules linked in:
27d4cce8:  [<081c13fe>] dump_stack+0x1c/0x20
27d4cd00:  [<08071aa0>] warn_slowpath_common+0x49/0x5f
27d4cd18:  [<08071acb>] warn_slowpath_null+0x15/0x19
27d4cd28:  [<0808fdb8>] __unqueue_futex+0x12/0x16
27d4cd38:  [<0808fef3>] futex_wait+0x137/0x1ed
27d4cdd0:  [<080910c3>] do_futex+0x78/0x7c4
27d4cedc:  [<080918e6>] sys_futex+0xd7/0xed
27d4cf28:  [<0805abf6>] handle_syscall+0x7a/0x98
27d4cf78:  [<080685d9>] userspace+0x2c9/0x370
27d4cfe0:  [<08058be5>] fork_handler+0x53/0x5b
27d4cffc:  [<00000000>] 0x0

---[ end trace ed7709f235f82328 ]---

!spin_is_locked(q->lock_ptr) in the WARN_ON() at line 786
triggers the warnings.

I'm not sure whether this shows a bug within UML
or the WARN_ON() is wrong.

What do you think?

-- 
Thanks,
//richard
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