• Tejun Heo's avatar
    9p-trans_fd: fix trans_fd::p9_conn_destroy() · 7dc5d24b
    Tejun Heo authored
    
    
    p9_conn_destroy() first kills all current requests by calling
    p9_conn_cancel(), then waits for the request list to be cleared by
    waiting on p9_conn->equeue.  After that, polling is stopped and the
    trans is destroyed.  This sequence has a few problems.
    
    * Read and write works were never cancelled and the p9_conn can be
      destroyed while the works are running as r/w works remove requests
      from the list and dereference the p9_conn from them.
    
    * The list emptiness wait using p9_conn->equeue wouldn't trigger
      because p9_conn_cancel() always clears all the lists and the only
      way the wait can be triggered is to have another task to issue a
      request between the slim window between p9_conn_cancel() and the
      wait, which isn't safe under the current implementation with or
      without the wait.
    
    This patch fixes the problem by first stopping poll, which can
    schedule r/w works, first and cancle r/w works which guarantees that
    r/w works are not and will not run from that point and then calling
    p9_conn_cancel() and do the rest of destruction.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Signed-off-by: default avatarEric Van Hensbergen <ericvh@gmail.com>
    7dc5d24b
trans_fd.c 35.4 KB