[libvirt] [PATCH] LXC: make sure fuse thread start to run before we do clone

[Gao feng]

On 11/08/2013 01:30 PM, Daniel P. Berrange wrote:
> On Thu, Nov 07, 2013 at 09:15:43PM +0800, Gao feng wrote:
>> I met a problem that container blocked by seteuid/setegid
>> which is call in lxcContainerSetID on UP system and libvirt
>> compiled with --with-fuse=yes.
>>
>> I looked into the glibc's codes, and found setxid in glibc
>> calls futex() to wait for other threads to change their
>> setxid_futex to 0(see setxid_mark_thread in glibc).
>>
>> since the process created by clone system call will not
>> share the memory with the other threads and the context
>> of memory doesn't changed until we call execl.(COW)
>>
>> So if the process which created by clone is called before
>> fuse thread being stated, the new setxid_futex of fuse
>> thread will not be saw in this process, it will be blocked
>> forever.
>>
>> Maybe this problem should be fixed in glibc, but I send
>> this patch as a quick fix.
> 
> Can you show a stack trace of the threads/processes deadlocking
> 

Daniel, chould you apply this patch? since this may not be fixed
in glibc quickly and we should conside libvirt works with buggy glibc.