checkpatch: Remove checks for expedited grace periods (98953135) · Commits · 戴 / test

There was a time when the expedited grace-period primitives (synchronize_rcu_expedited(), synchronize_rcu_bh_expedited(), and synchronize_sched_expedited()) used rather antisocial kernel facilities like try_stop_cpus(). However, they have since been housebroken to use only single-CPU IPIs, and typically cause less disturbance than a scheduling-clock interrupt. Furthermore, this disturbance can be eliminated entirely using NO_HZ_FULL on the one hand or the rcupdate.rcu_normal boot parameter on the other. This commit therefore removes checkpatch's complaints about use of the expedited RCU primitives. Signed-off-by:

Paul E. McKenney <paulmck@linux.vnet.ibm.com>

scripts/checkpatch.pl

+0 −17

Original line number	Diff line number	Diff line
		@@ -5533,23 +5533,6 @@ sub process {
		}
		}

		# 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)\(/) {
		WARN("EXPEDITED_RCU_GRACE_PERIOD",
		"expedited RCU grace periods should be avoided where they can degrade real-time response\n" . $herecurr);

		}

		# check of hardware specific defines
		if ($line =~ m@^.\s\#\sif.*\b(__i386__\|__powerpc64__\|__sun__\|__s390x__)\b@ && $realfile !~ m@include/asm-@) {
		CHK("ARCH_DEFINES",

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