• WANG Cong's avatar
    af_unix: conditionally use freezable blocking calls in read · 06a77b07
    WANG Cong authored
    Commit 2b15af6f ("af_unix: use freezable blocking calls in read")
    converts schedule_timeout() to its freezable version, it was probably
    correct at that time, but later, commit 2b514574
    ("net: af_unix: implement splice for stream af_unix sockets") breaks
    the strong requirement for a freezable sleep, according to
    commit 0f9548ca:
    
        We shouldn't try_to_freeze if locks are held.  Holding a lock can cause a
        deadlock if the lock is later acquired in the suspend or hibernate path
        (e.g.  by dpm).  Holding a lock can also cause a deadlock in the case of
        cgroup_freezer if a lock is held inside a frozen cgroup that is later
        acquired by a process outside that group.
    
    The pipe_lock is still held at that point.
    
    So use freezable version only for the recvmsg call path, avoid impact for
    Android.
    
    Fixes: 2b514574 ("net: af_unix: implement splice for stream af_unix sockets")
    Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: Colin Cross <ccross@android.com>
    Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
    Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
    Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    06a77b07
af_unix.c 67.6 KB