[PATCH v3 2/4] rcu: Cleanup the variables used to request a new grace period
From: Joel Fernandes
Date: Sun May 20 2018 - 23:47:37 EST
The 'c' variable was used previously to store the grace period that is
being requested. However it is not very meaningful since the gp_seq
conversions. This patch replaces it with gp_seq_req indicating that
this is the grace period that was requested. Also updating tracing with
the new name.
Previous patch discussion is at:
https://patchwork.kernel.org/patch/10396579/
Signed-off-by: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
---
include/trace/events/rcu.h | 15 ++++++------
kernel/rcu/tree.c | 50 ++++++++++++++++++++++----------------
2 files changed, 37 insertions(+), 28 deletions(-)
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 5373bc61ae08..a8d07feff6a0 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -103,15 +103,16 @@ TRACE_EVENT(rcu_grace_period,
*/
TRACE_EVENT(rcu_future_grace_period,
- TP_PROTO(const char *rcuname, unsigned long gp_seq, unsigned long c,
- u8 level, int grplo, int grphi, const char *gpevent),
+ TP_PROTO(const char *rcuname, unsigned long gp_seq,
+ unsigned long gp_seq_req, u8 level, int grplo, int grphi,
+ const char *gpevent),
- TP_ARGS(rcuname, gp_seq, c, level, grplo, grphi, gpevent),
+ TP_ARGS(rcuname, gp_seq, gp_seq_req, level, grplo, grphi, gpevent),
TP_STRUCT__entry(
__field(const char *, rcuname)
__field(unsigned long, gp_seq)
- __field(unsigned long, c)
+ __field(unsigned long, gp_seq_req)
__field(u8, level)
__field(int, grplo)
__field(int, grphi)
@@ -121,7 +122,7 @@ TRACE_EVENT(rcu_future_grace_period,
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->gp_seq = gp_seq;
- __entry->c = c;
+ __entry->gp_seq_req = gp_seq_req;
__entry->level = level;
__entry->grplo = grplo;
__entry->grphi = grphi;
@@ -129,7 +130,7 @@ TRACE_EVENT(rcu_future_grace_period,
),
TP_printk("%s %lu %lu %u %d %d %s",
- __entry->rcuname, __entry->gp_seq, __entry->c, __entry->level,
+ __entry->rcuname, __entry->gp_seq, __entry->gp_seq_req, __entry->level,
__entry->grplo, __entry->grphi, __entry->gpevent)
);
@@ -751,7 +752,7 @@ TRACE_EVENT(rcu_barrier,
#else /* #ifdef CONFIG_RCU_TRACE */
#define trace_rcu_grace_period(rcuname, gp_seq, gpevent) do { } while (0)
-#define trace_rcu_future_grace_period(rcuname, gp_seq, c, \
+#define trace_rcu_future_grace_period(rcuname, gp_seq, gp_seq_req, \
level, grplo, grphi, event) \
do { } while (0)
#define trace_rcu_grace_period_init(rcuname, gp_seq, level, grplo, grphi, \
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 2c06e1ab90cd..0ffd41ba304f 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1518,13 +1518,18 @@ void rcu_cpu_stall_reset(void)
/* Trace-event wrapper function for trace_rcu_future_grace_period. */
static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
- unsigned long c, const char *s)
+ unsigned long gp_seq_req, const char *s)
{
- trace_rcu_future_grace_period(rdp->rsp->name, rnp->gp_seq, c,
+ trace_rcu_future_grace_period(rdp->rsp->name, rnp->gp_seq, gp_seq_req,
rnp->level, rnp->grplo, rnp->grphi, s);
}
/*
+ * rcu_start_this_gp - Request the start of a particular grace period
+ * @rnp: The leaf node of the CPU from which to start.
+ * @rdp: The rcu_data corresponding to the CPU from which to start.
+ * @gp_seq_req: The gp_seq of the grace period to start.
+ *
* Start the specified grace period, as needed to handle newly arrived
* callbacks. The required future grace periods are recorded in each
* rcu_node structure's ->gp_seq_needed field. Returns true if there
@@ -1532,9 +1537,11 @@ static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
*
* The caller must hold the specified rcu_node structure's ->lock, which
* is why the caller is responsible for waking the grace-period kthread.
+ *
+ * Returns true if the GP thread needs to be awakened else false.
*/
static bool rcu_start_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
- unsigned long c)
+ unsigned long gp_seq_req)
{
bool ret = false;
struct rcu_state *rsp = rdp->rsp;
@@ -1550,25 +1557,27 @@ static bool rcu_start_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
* not be released.
*/
raw_lockdep_assert_held_rcu_node(rnp);
- trace_rcu_this_gp(rnp, rdp, c, TPS("Startleaf"));
+ trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startleaf"));
for (rnp_root = rnp; 1; rnp_root = rnp_root->parent) {
if (rnp_root != rnp)
raw_spin_lock_rcu_node(rnp_root);
- if (ULONG_CMP_GE(rnp_root->gp_seq_needed, c) ||
- rcu_seq_started(&rnp_root->gp_seq, c) ||
+ if (ULONG_CMP_GE(rnp_root->gp_seq_needed, gp_seq_req) ||
+ rcu_seq_started(&rnp_root->gp_seq, gp_seq_req) ||
(rnp != rnp_root &&
rcu_seq_state(rcu_seq_current(&rnp_root->gp_seq)))) {
- trace_rcu_this_gp(rnp_root, rdp, c, TPS("Prestarted"));
+ trace_rcu_this_gp(rnp_root, rdp, gp_seq_req,
+ TPS("Prestarted"));
goto unlock_out;
}
- rnp_root->gp_seq_needed = c;
+ rnp_root->gp_seq_needed = gp_seq_req;
if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) {
/*
* We just marked the leaf, and a grace period
* is in progress, which means that rcu_gp_cleanup()
* will see the marking. Bail to reduce contention.
*/
- trace_rcu_this_gp(rnp, rdp, c, TPS("Startedleaf"));
+ trace_rcu_this_gp(rnp, rdp, gp_seq_req,
+ TPS("Startedleaf"));
goto unlock_out;
}
if (rnp_root != rnp && rnp_root->parent != NULL)
@@ -1579,14 +1588,14 @@ static bool rcu_start_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
/* If GP already in progress, just leave, otherwise start one. */
if (rcu_gp_in_progress(rsp)) {
- trace_rcu_this_gp(rnp_root, rdp, c, TPS("Startedleafroot"));
+ trace_rcu_this_gp(rnp_root, rdp, gp_seq_req, TPS("Startedleafroot"));
goto unlock_out;
}
- trace_rcu_this_gp(rnp_root, rdp, c, TPS("Startedroot"));
+ trace_rcu_this_gp(rnp_root, rdp, gp_seq_req, TPS("Startedroot"));
WRITE_ONCE(rsp->gp_flags, rsp->gp_flags | RCU_GP_FLAG_INIT);
rsp->gp_req_activity = jiffies;
if (!rsp->gp_kthread) {
- trace_rcu_this_gp(rnp_root, rdp, c, TPS("NoGPkthread"));
+ trace_rcu_this_gp(rnp_root, rdp, gp_seq_req, TPS("NoGPkthread"));
goto unlock_out;
}
trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gp_seq), TPS("newreq"));
@@ -1595,9 +1604,9 @@ static bool rcu_start_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
if (rnp != rnp_root)
raw_spin_unlock_rcu_node(rnp_root);
/* Push furthest requested GP to leaf node and rcu_data structure. */
- if (ULONG_CMP_GE(rnp_root->gp_seq_needed, c)) {
- rnp->gp_seq_needed = c;
- rdp->gp_seq_needed = c;
+ if (ULONG_CMP_GE(rnp_root->gp_seq_needed, gp_seq_req)) {
+ rnp->gp_seq_needed = gp_seq_req;
+ rdp->gp_seq_needed = gp_seq_req;
}
return ret;
}
@@ -1608,14 +1617,13 @@ static bool rcu_start_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
*/
static bool rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp)
{
- unsigned long c = rnp->gp_seq;
bool needmore;
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
needmore = ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed);
if (!needmore)
rnp->gp_seq_needed = rnp->gp_seq; /* Avoid counter wrap. */
- trace_rcu_this_gp(rnp, rdp, c,
+ trace_rcu_this_gp(rnp, rdp, rnp->gp_seq,
needmore ? TPS("CleanupMore") : TPS("Cleanup"));
return needmore;
}
@@ -1651,7 +1659,7 @@ static void rcu_gp_kthread_wake(struct rcu_state *rsp)
static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
struct rcu_data *rdp)
{
- unsigned long c;
+ unsigned long gp_seq_req;
bool ret = false;
raw_lockdep_assert_held_rcu_node(rnp);
@@ -1670,9 +1678,9 @@ static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
* accelerating callback invocation to an earlier grace-period
* number.
*/
- c = rcu_seq_snap(&rsp->gp_seq);
- if (rcu_segcblist_accelerate(&rdp->cblist, c))
- ret = rcu_start_this_gp(rnp, rdp, c);
+ gp_seq_req = rcu_seq_snap(&rsp->gp_seq);
+ if (rcu_segcblist_accelerate(&rdp->cblist, gp_seq_req))
+ ret = rcu_start_this_gp(rnp, rdp, gp_seq_req);
/* Trace depending on how much we were able to accelerate. */
if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL))
--
2.17.0.441.gb46fe60e1d-goog