• Alan Stern's avatar
    [PATCH] Add SRCU-based notifier chains · eabc0694
    Alan Stern authored
    
    
    This patch (as751) adds a new type of notifier chain, based on the SRCU
    (Sleepable Read-Copy Update) primitives recently added to the kernel.  An
    SRCU notifier chain is much like a blocking notifier chain, in that it must
    be called in process context and its callout routines are allowed to sleep.
     The difference is that the chain's links are protected by the SRCU
    mechanism rather than by an rw-semaphore, so calling the chain has
    extremely low overhead: no memory barriers and no cache-line bouncing.  On
    the other hand, unregistering from the chain is expensive and the chain
    head requires special runtime initialization (plus cleanup if it is to be
    deallocated).
    
    SRCU notifiers are appropriate for notifiers that will be called very
    frequently and for which unregistration occurs very seldom.  The proposed
    "task notifier" scheme qualifies, as may some of the network notifiers.
    Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
    Acked-by: default avatarPaul E. McKenney <paulmck@us.ibm.com>
    Acked-by: default avatarChandra Seetharaman <sekharan@us.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    eabc0694