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Bluetooth: Fix nested sleeps

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l2cap/rfcomm/sco_sock_accept() are wait loops which may acquire
sleeping locks. Since both wait loops and sleeping locks use
task_struct.state to sleep and wake, the nested sleeping locks
destroy the wait loop state.

Use the newly-minted wait_woken() and DEFINE_WAIT_FUNC() for the
wait loop. DEFINE_WAIT_FUNC() allows an alternate wake function
to be specified; in this case, the predefined scheduler function,
woken_wake_function(). This wait construct ensures wakeups will
not be missed without requiring the wait loop to set the
task state before condition evaluation. How this works:

 CPU 0                            |  CPU 1
                                  |
                                  | is <condition> set?
                                  | no
set <condition>                   |
                                  |
wake_up_interruptible             |
  woken_wake_function             |
    set WQ_FLAG_WOKEN             |
    try_to_wake_up                |
                                  | wait_woken
                                  |   set TASK_INTERRUPTIBLE
                                  |   WQ_FLAG_WOKEN? yes
                                  |   set TASK_RUNNING
                                  |
                                  | - loop -
				  |
				  | is <condition> set?
                                  | yes - exit wait loop

Fixes "do not call blocking ops when !TASK_RUNNING" warnings
in l2cap_sock_accept(), rfcomm_sock_accept() and sco_sock_accept().

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>
This commit is contained in:
Peter Hurley 2015-01-23 12:16:53 -05:00 • committed by Johan Hedberg
commit dfb2fae7cd
3 changed files with 11 additions and 15 deletions
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