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Date: Mon, 25 Jun 2018 17:08:55 -0700
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: linux-kernel@...r.kernel.org
Cc: mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 36/40] rcutorture: Correctly handle grace-period sequence wrap
The new ->gq_seq grace-period sequence numbers must be shifted down,
which give artifacts when these numbers wrap. This commit therefore
enables rcutorture and rcuperf to handle grace-period sequence numbers
even if they do wrap. It does this by allowing a special subtraction
function to be specified, and this function subtracts before shifting.
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
kernel/rcu/rcu.h | 9 +++++++++
kernel/rcu/rcuperf.c | 18 ++++++++++++++++--
kernel/rcu/rcutorture.c | 19 +++++++++++++------
kernel/rcu/tree.c | 6 +++---
4 files changed, 41 insertions(+), 11 deletions(-)
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 1c5cbd9d7c97..aa215d6355f8 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -142,6 +142,15 @@ static inline bool rcu_seq_new_gp(unsigned long old, unsigned long new)
new);
}
+/*
+ * Roughly how many full grace periods have elapsed between the collection
+ * of the two specified grace periods?
+ */
+static inline unsigned long rcu_seq_diff(unsigned long new, unsigned long old)
+{
+ return (new - old) >> RCU_SEQ_CTR_SHIFT;
+}
+
/*
* debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
* by call_rcu() and rcu callback execution, and are therefore not part of the
diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
index 2b5a613afcf3..b080bc4a4f45 100644
--- a/kernel/rcu/rcuperf.c
+++ b/kernel/rcu/rcuperf.c
@@ -139,6 +139,7 @@ struct rcu_perf_ops {
int (*readlock)(void);
void (*readunlock)(int idx);
unsigned long (*get_gp_seq)(void);
+ unsigned long (*gp_diff)(unsigned long new, unsigned long old);
unsigned long (*exp_completed)(void);
void (*async)(struct rcu_head *head, rcu_callback_t func);
void (*gp_barrier)(void);
@@ -179,6 +180,7 @@ static struct rcu_perf_ops rcu_ops = {
.readlock = rcu_perf_read_lock,
.readunlock = rcu_perf_read_unlock,
.get_gp_seq = rcu_get_gp_seq,
+ .gp_diff = rcu_seq_diff,
.exp_completed = rcu_exp_batches_completed,
.async = call_rcu,
.gp_barrier = rcu_barrier,
@@ -208,6 +210,7 @@ static struct rcu_perf_ops rcu_bh_ops = {
.readlock = rcu_bh_perf_read_lock,
.readunlock = rcu_bh_perf_read_unlock,
.get_gp_seq = rcu_bh_get_gp_seq,
+ .gp_diff = rcu_seq_diff,
.exp_completed = rcu_exp_batches_completed_sched,
.async = call_rcu_bh,
.gp_barrier = rcu_barrier_bh,
@@ -264,6 +267,7 @@ static struct rcu_perf_ops srcu_ops = {
.readlock = srcu_perf_read_lock,
.readunlock = srcu_perf_read_unlock,
.get_gp_seq = srcu_perf_completed,
+ .gp_diff = rcu_seq_diff,
.exp_completed = srcu_perf_completed,
.async = srcu_call_rcu,
.gp_barrier = srcu_rcu_barrier,
@@ -292,6 +296,7 @@ static struct rcu_perf_ops srcud_ops = {
.readlock = srcu_perf_read_lock,
.readunlock = srcu_perf_read_unlock,
.get_gp_seq = srcu_perf_completed,
+ .gp_diff = rcu_seq_diff,
.exp_completed = srcu_perf_completed,
.async = srcu_call_rcu,
.gp_barrier = srcu_rcu_barrier,
@@ -321,6 +326,7 @@ static struct rcu_perf_ops sched_ops = {
.readlock = sched_perf_read_lock,
.readunlock = sched_perf_read_unlock,
.get_gp_seq = rcu_sched_get_gp_seq,
+ .gp_diff = rcu_seq_diff,
.exp_completed = rcu_exp_batches_completed_sched,
.async = call_rcu_sched,
.gp_barrier = rcu_barrier_sched,
@@ -348,6 +354,7 @@ static struct rcu_perf_ops tasks_ops = {
.readlock = tasks_perf_read_lock,
.readunlock = tasks_perf_read_unlock,
.get_gp_seq = rcu_no_completed,
+ .gp_diff = rcu_seq_diff,
.async = call_rcu_tasks,
.gp_barrier = rcu_barrier_tasks,
.sync = synchronize_rcu_tasks,
@@ -355,6 +362,13 @@ static struct rcu_perf_ops tasks_ops = {
.name = "tasks"
};
+static unsigned long rcuperf_seq_diff(unsigned long new, unsigned long old)
+{
+ if (!cur_ops->gp_diff)
+ return new - old;
+ return cur_ops->gp_diff(new, old);
+}
+
static bool __maybe_unused torturing_tasks(void)
{
return cur_ops == &tasks_ops;
@@ -577,8 +591,8 @@ rcu_perf_cleanup(void)
t_rcu_perf_writer_finished -
t_rcu_perf_writer_started,
ngps,
- b_rcu_perf_writer_finished -
- b_rcu_perf_writer_started);
+ rcuperf_seq_diff(b_rcu_perf_writer_finished,
+ b_rcu_perf_writer_started));
for (i = 0; i < nrealwriters; i++) {
if (!writer_durations)
break;
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 81fb43530d64..0481c7286875 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -265,6 +265,7 @@ struct rcu_torture_ops {
void (*read_delay)(struct torture_random_state *rrsp);
void (*readunlock)(int idx);
unsigned long (*get_gp_seq)(void);
+ unsigned long (*gp_diff)(unsigned long new, unsigned long old);
void (*deferred_free)(struct rcu_torture *p);
void (*sync)(void);
void (*exp_sync)(void);
@@ -400,6 +401,7 @@ static struct rcu_torture_ops rcu_ops = {
.read_delay = rcu_read_delay,
.readunlock = rcu_torture_read_unlock,
.get_gp_seq = rcu_get_gp_seq,
+ .gp_diff = rcu_seq_diff,
.deferred_free = rcu_torture_deferred_free,
.sync = synchronize_rcu,
.exp_sync = synchronize_rcu_expedited,
@@ -441,6 +443,7 @@ static struct rcu_torture_ops rcu_bh_ops = {
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = rcu_bh_torture_read_unlock,
.get_gp_seq = rcu_bh_get_gp_seq,
+ .gp_diff = rcu_seq_diff,
.deferred_free = rcu_bh_torture_deferred_free,
.sync = synchronize_rcu_bh,
.exp_sync = synchronize_rcu_bh_expedited,
@@ -646,6 +649,7 @@ static struct rcu_torture_ops sched_ops = {
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = sched_torture_read_unlock,
.get_gp_seq = rcu_sched_get_gp_seq,
+ .gp_diff = rcu_seq_diff,
.deferred_free = rcu_sched_torture_deferred_free,
.sync = synchronize_sched,
.exp_sync = synchronize_sched_expedited,
@@ -695,6 +699,13 @@ static struct rcu_torture_ops tasks_ops = {
.name = "tasks"
};
+static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
+{
+ if (!cur_ops->gp_diff)
+ return new - old;
+ return cur_ops->gp_diff(new, old);
+}
+
static bool __maybe_unused torturing_tasks(void)
{
return cur_ops == &tasks_ops;
@@ -1127,9 +1138,7 @@ static void rcu_torture_timer(struct timer_list *unused)
rcu_ftrace_dump(DUMP_ALL);
}
__this_cpu_inc(rcu_torture_count[pipe_count]);
- completed = completed - started;
- if (completed > ULONG_MAX >> 1)
- completed = 0; /* Not all gp_seq have full range. */
+ completed = rcutorture_seq_diff(completed, started);
if (completed > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
completed = RCU_TORTURE_PIPE_LEN;
@@ -1205,9 +1214,7 @@ rcu_torture_reader(void *arg)
rcu_ftrace_dump(DUMP_ALL);
}
__this_cpu_inc(rcu_torture_count[pipe_count]);
- completed = completed - started;
- if (completed > ULONG_MAX >> 1)
- completed = 0; /* Not all gp_seq have full range. */
+ completed = rcutorture_seq_diff(completed, started);
if (completed > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
completed = RCU_TORTURE_PIPE_LEN;
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 446163b6feba..fa82f0413d2c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -532,7 +532,7 @@ static int rcu_pending(void);
*/
unsigned long rcu_get_gp_seq(void)
{
- return rcu_seq_ctr(READ_ONCE(rcu_state_p->gp_seq));
+ return READ_ONCE(rcu_state_p->gp_seq);
}
EXPORT_SYMBOL_GPL(rcu_get_gp_seq);
@@ -541,7 +541,7 @@ EXPORT_SYMBOL_GPL(rcu_get_gp_seq);
*/
unsigned long rcu_sched_get_gp_seq(void)
{
- return rcu_seq_ctr(READ_ONCE(rcu_sched_state.gp_seq));
+ return READ_ONCE(rcu_sched_state.gp_seq);
}
EXPORT_SYMBOL_GPL(rcu_sched_get_gp_seq);
@@ -550,7 +550,7 @@ EXPORT_SYMBOL_GPL(rcu_sched_get_gp_seq);
*/
unsigned long rcu_bh_get_gp_seq(void)
{
- return rcu_seq_ctr(READ_ONCE(rcu_bh_state.gp_seq));
+ return READ_ONCE(rcu_bh_state.gp_seq);
}
EXPORT_SYMBOL_GPL(rcu_bh_get_gp_seq);
--
2.17.1
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