• Paul E. McKenney's avatar
    rcu: Remove restrictions on no-CBs CPUs · 34ed6246
    Paul E. McKenney authored
    Currently, CPU 0 is constrained to not be a no-CBs CPU, and furthermore
    at least one no-CBs CPU must remain online at any given time.  These
    restrictions are problematic in some situations, such as cases where
    all CPUs must run a real-time workload that needs to be insulated from
    OS jitter and latencies due to RCU callback invocation.  This commit
    therefore provides no-CBs CPUs a (very crude and energy-inefficient)
    way to start and to wait for grace periods independently of the normal
    RCU callback mechanisms.  This approach allows any or all of the CPUs to
    be designated as no-CBs CPUs, and allows any proper subset of the CPUs
    (whether no-CBs CPUs or not) to be offlined.
    
    This commit also provides a fix for a locking bug spotted by Xie
    ChanglongX <changlongx.xie@intel.com>.
    Signed-off-by: default avatarPaul E. McKenney <paul.mckenney@linaro.org>
    Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    34ed6246
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