• Paul E. McKenney's avatar
    rcu: Merge preemptable-RCU functionality into hierarchical RCU · f41d911f
    Paul E. McKenney authored
    Create a kernel/rcutree_plugin.h file that contains definitions
    for preemptable RCU (or, under the #else branch of the #ifdef,
    empty definitions for the classic non-preemptable semantics).
    These definitions fit into plugins defined in kernel/rcutree.c
    for this purpose.
    
    This variant of preemptable RCU uses a new algorithm whose
    read-side expense is roughly that of classic hierarchical RCU
    under CONFIG_PREEMPT. This new algorithm's update-side expense
    is similar to that of classic hierarchical RCU, and, in absence
    of read-side preemption or blocking, is exactly that of classic
    hierarchical RCU.  Perhaps more important, this new algorithm
    has a much simpler implementation, saving well over 1,000 lines
    of code compared to mainline's implementation of preemptable
    RCU, which will hopefully be retired in favor of this new
    algorithm.
    
    The simplifications are obtained by maintaining per-task
    nesting state for running tasks, and using a simple
    lock-protected algorithm to handle accounting when tasks block
    within RCU read-side critical sections, making use of lessons
    learned while creating numerous user-level RCU implementations
    over the past 18 months.
    Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    Cc: laijs@cn.fujitsu.com
    Cc: dipankar@in.ibm.com
    Cc: akpm@linux-foundation.org
    Cc: mathieu.desnoyers@polymtl.ca
    Cc: josht@linux.vnet.ibm.com
    Cc: dvhltc@us.ibm.com
    Cc: niv@us.ibm.com
    Cc: peterz@infradead.org
    Cc: rostedt@goodmis.org
    LKML-Reference: <12509746134003-git-send-email->
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    f41d911f
rcutree_trace.c 9.08 KB