Re: [BUG] 2.2.1[78] : RTNETLINK lock not properly locking ?

[Willy Tarreau <willy.lkml@free.fr>]

> No, it guarentees that only one process may be in the middle
> of modifying interface configuration state, the same and only
> guarentee it makes in 2.4.x as well.

ok, Dave. But the code in dev_ioctl() actually is :

  rtnl_lock();
  ret = dev_ifsioc(&ifr, cmd);
  rtnl_unlock();

if only these lock/unlock guarantee this atomicity, then I can't
see why my A,B,C case could not work. If this is because the
kernel has been locked somewhere else, then why are the locks
still needed ? The author of rtnetlink.h has been very precautious
about the atomicity of these locks when CONFIG_RTNETLINK is set. I
don't understand why this could change in other cases. For this
reason, I don't know what to write in my code ...

Regards,
Willy
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