Commit fd863448 authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by Paolo Abeni
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af_unix: Try not to hold unix_gc_lock during accept(). 



Commit dcf70df2 ("af_unix: Fix up unix_edge.successor for embryo
socket.") added spin_lock(&unix_gc_lock) in accept() path, and it
caused regression in a stress test as reported by kernel test robot.

If the embryo socket is not part of the inflight graph, we need not
hold the lock.

To decide that in O(1) time and avoid the regression in the normal
use case,

  1. add a new stat unix_sk(sk)->scm_stat.nr_unix_fds

  2. count the number of inflight AF_UNIX sockets in the receive
     queue under unix_state_lock()

  3. move unix_update_edges() call under unix_state_lock()

  4. avoid locking if nr_unix_fds is 0 in unix_update_edges()

Reported-by: default avatarkernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202404101427.92a08551-oliver.sang@intel.com


Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240413021928.20946-1-kuniyu@amazon.com


Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
parent e918c7bb
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