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authorPaul E. McKenney <paul.mckenney@linaro.org>2011-06-27 00:17:43 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2011-09-28 21:38:22 -0700
commite4cc1f22b2f4e9b0207a8cdb63e56dcf99e82d35 (patch)
treeec3fad6587f0a83e764a571394bdfb85a84edf30 /kernel/rcutree_trace.c
parentd4c08f2ac311a360230eef7e5395b0ec8d8f0670 (diff)
downloadlinaro-lsk-e4cc1f22b2f4e9b0207a8cdb63e56dcf99e82d35.tar.gz
rcu: Simplify quiescent-state accounting
There is often a delay between the time that a CPU passes through a quiescent state and the time that this quiescent state is reported to the RCU core. It is quite possible that the grace period ended before the quiescent state could be reported, for example, some other CPU might have deduced that this CPU passed through dyntick-idle mode. It is critically important that quiescent state be counted only against the grace period that was in effect at the time that the quiescent state was detected. Previously, this was handled by recording the number of the last grace period to complete when passing through a quiescent state. The RCU core then checks this number against the current value, and rejects the quiescent state if there is a mismatch. However, one additional possibility must be accounted for, namely that the quiescent state was recorded after the prior grace period completed but before the current grace period started. In this case, the RCU core must reject the quiescent state, but the recorded number will match. This is handled when the CPU becomes aware of a new grace period -- at that point, it invalidates any prior quiescent state. This works, but is a bit indirect. The new approach records the current grace period, and the RCU core checks to see (1) that this is still the current grace period and (2) that this grace period has not yet ended. This approach simplifies reasoning about correctness, and this commit changes over to this new approach. Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree_trace.c')
-rw-r--r--kernel/rcutree_trace.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index f328ed1c6e4..9feffa4c069 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -61,11 +61,11 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
{
if (!rdp->beenonline)
return;
- seq_printf(m, "%3d%cc=%lu g=%lu pq=%d pqc=%lu qp=%d",
+ seq_printf(m, "%3d%cc=%lu g=%lu pq=%d pgp=%lu qp=%d",
rdp->cpu,
cpu_is_offline(rdp->cpu) ? '!' : ' ',
rdp->completed, rdp->gpnum,
- rdp->passed_quiesc, rdp->passed_quiesc_completed,
+ rdp->passed_quiesce, rdp->passed_quiesce_gpnum,
rdp->qs_pending);
#ifdef CONFIG_NO_HZ
seq_printf(m, " dt=%d/%d/%d df=%lu",
@@ -139,7 +139,7 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
rdp->cpu,
cpu_is_offline(rdp->cpu) ? "\"N\"" : "\"Y\"",
rdp->completed, rdp->gpnum,
- rdp->passed_quiesc, rdp->passed_quiesc_completed,
+ rdp->passed_quiesce, rdp->passed_quiesce_gpnum,
rdp->qs_pending);
#ifdef CONFIG_NO_HZ
seq_printf(m, ",%d,%d,%d,%lu",
@@ -170,7 +170,7 @@ static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
static int show_rcudata_csv(struct seq_file *m, void *unused)
{
- seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pqc\",\"pq\",");
+ seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pgp\",\"pq\",");
#ifdef CONFIG_NO_HZ
seq_puts(m, "\"dt\",\"dt nesting\",\"dt NMI nesting\",\"df\",");
#endif /* #ifdef CONFIG_NO_HZ */