From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com,
bobby.prani@gmail.com,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH v2 tip/core/rcu 02/11] rcu: Clarify role of ->expmaskinitnext
Date: Wed, 9 Dec 2015 15:02:59 -0800 [thread overview]
Message-ID: <1449702188-493-2-git-send-email-paulmck@linux.vnet.ibm.com> (raw)
In-Reply-To: <20151209230243.GA32518@linux.vnet.ibm.com>
Analogy with the ->qsmaskinitnext field might lead one to believe that
->expmaskinitnext tracks online CPUs. This belief is incorrect: Any CPU
that has ever been online will have its bit set in the ->expmaskinitnext
field. This commit therefore adds a comment to make this clear, at
least to people who read comments.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcu/tree.h | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index f32bebb6bc90..8151971a8978 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -178,6 +178,8 @@ struct rcu_node {
/* beginning of each expedited GP. */
unsigned long expmaskinitnext;
/* Online CPUs for next expedited GP. */
+ /* Any CPU that has ever been online will */
+ /* have its bit set. */
unsigned long grpmask; /* Mask to apply to parent qsmask. */
/* Only one bit will be set in this mask. */
int grplo; /* lowest-numbered CPU or group here. */
--
2.5.2
next prev parent reply other threads:[~2015-12-09 23:03 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-09 23:02 [PATCH v2 tip/core/rcu 0/11] Expedited-grace-period changes for 4.5 Paul E. McKenney
2015-12-09 23:02 ` [PATCH v2 tip/core/rcu 01/11] rcu: Short-circuit synchronize_sched_expedited() if only one CPU Paul E. McKenney
2015-12-09 23:02 ` Paul E. McKenney [this message]
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 03/11] rcu: Move smp_mb() from rcu_seq_snap() to rcu_exp_gp_seq_snap() Paul E. McKenney
2015-12-10 20:29 ` Peter Zijlstra
2015-12-10 20:41 ` Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 04/11] rcu: Invert sync_rcu_exp_select_cpus() "if" statement Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 05/11] rcu: Reduce expedited GP memory contention via per-CPU variables Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 06/11] rcu: Make expedited grace periods resolve stall-warning ties Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 07/11] rcu: Add more diagnostics to expedited stall warning messages Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 08/11] rcu: Add rcu_normal kernel parameter to suppress expediting Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 09/11] rcu: Wire up rcu_end_inkernel_boot() Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 10/11] rcu: Allow expedited grace periods to be disabled at init Paul E. McKenney
2015-12-09 23:03 ` [PATCH v2 tip/core/rcu 11/11] rcu: Remove TINY_RCU bloat from pointless boot parameters Paul E. McKenney
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