• Martin Schwidefsky's avatar
    [PATCH] s390: spin lock retry · 951f22d5
    Martin Schwidefsky authored
    
    
    Split spin lock and r/w lock implementation into a single try which is done
    inline and an out of line function that repeatedly tries to get the lock
    before doing the cpu_relax().  Add a system control to set the number of
    retries before a cpu is yielded.
    
    The reason for the spin lock retry is that the diagnose 0x44 that is used to
    give up the virtual cpu is quite expensive.  For spin locks that are held only
    for a short period of time the costs of the diagnoses outweights the savings
    for spin locks that are held for a longer timer.  The default retry count is
    1000.
    Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
    951f22d5