On Fri, 2015-07-17 at 15:20 -0700, Paul E. McKenney wrote: > The synchronize_rcu_expedited() and synchronize_sched_expedited() > expedited-grace-period primitives induce OS jitter, which can degrade > real-time response. This commit therefore adds a checkpatch.pl warning > on any patch adding them. [] > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl [] > +# Check for expedited grace periods that interrupt non-idle non-nohz > +# online CPUs. These expedited can therefore degrade real-time response > +# if used carelessly, and should be avoided where not absolutely > +# needed. It is always OK to use synchronize_rcu_expedited() and > +# synchronize_sched_expedited() at boot time (before real-time applications > +# start) and in error situations where real-time response is compromised in > +# any case. Note that synchronize_srcu_expedited() does -not- interrupt > +# other CPUs, so don't warn on uses of synchronize_srcu_expedited(). > +# Of course, nothing comes for free, and srcu_read_lock() and > +# srcu_read_unlock() do contain full memory barriers in payment for > +# synchronize_srcu_expedited() non-interruption properties. > + if ($line =~ > /\b(synchronize_rcu_expedited|synchronize_sched_expedited)\(/) {
It'd be faster perl without capture groups: if ($line =~ /\b(?:synchronize_(?:rcu|sched)_expedited)\s*\(/) { > + WARN("EXPEDITED_RCU_GRACE_PERIOD", > + "expedited RCU grace periods should be avoided in > cases where they can degrade real-time response\n" . $herecurr); "in cases" is rather redundant. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/