1. 21 Nov, 2012 1 commit
    • Ying Xue's avatar
      tipc: fix race/inefficiencies in poll/wait behaviour · f288bef4
      Ying Xue authored
      When an application blocks at poll/select on a TIPC socket
      while requesting a specific event mask, both the filter_rcv() and
      wakeupdispatch() case will wake it up unconditionally whenever
      the state changes (i.e an incoming message arrives, or congestion
      has subsided).  No mask is used.
      
      To avoid this, we populate sk->sk_data_ready and sk->sk_write_space
      with tipc_data_ready and tipc_write_space respectively, which makes
      tipc more in alignment with the rest of the networking code.  These
      pass the exact set of possible events to the waker in fs/select.c
      hence avoiding waking up blocked processes unnecessarily.
      
      In doing so, we uncover another issue -- that there needs to be a
      memory barrier in these poll/receive callbacks, otherwise we are
      subject to the the same race as documented above wq_has_sleeper()
      [in commit a57de0b4 "net: adding memory barrier to the poll and
      receive callbacks"].  So we need to replace poll_wait() with
      sock_poll_wait() and use rcu protection for the sk->sk_wq pointer
      in these two new functions.
      Signed-off-by: default avatarYing Xue <ying.xue@windriver.com>
      Signed-off-by: default avatarPaul Gortmaker <paul.gortmaker@windriver.com>
      f288bef4
  2. 20 Nov, 2012 11 commits
  3. 19 Nov, 2012 28 commits