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Merge branch 'gp.2013.09.25a' into HEAD

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gp.2013.09.25a: Topic branch for grace-period updates.
This commit is contained in:
Paul E. McKenney 2013-10-15 12:47:04 -07:00
commit 25e03a74e4
4 changed files with 144 additions and 29 deletions
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80
include/trace/events/rcu.h
View File

@ -39,15 +39,26 @@ TRACE_EVENT(rcu_utilization,
#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
/*
* Tracepoint for grace-period events: starting and ending a grace
* period ("start" and "end", respectively), a CPU noting the start
* of a new grace period or the end of an old grace period ("cpustart"
* and "cpuend", respectively), a CPU passing through a quiescent
* state ("cpuqs"), a CPU coming online or going offline ("cpuonl"
* and "cpuofl", respectively), a CPU being kicked for being too
* long in dyntick-idle mode ("kick"), a CPU accelerating its new
* callbacks to RCU_NEXT_READY_TAIL ("AccReadyCB"), and a CPU
* accelerating its new callbacks to RCU_WAIT_TAIL ("AccWaitCB").
* Tracepoint for grace-period events. Takes a string identifying the
* RCU flavor, the grace-period number, and a string identifying the
* grace-period-related event as follows:
*
* "AccReadyCB": CPU acclerates new callbacks to RCU_NEXT_READY_TAIL.
* "AccWaitCB": CPU accelerates new callbacks to RCU_WAIT_TAIL.
* "newreq": Request a new grace period.
* "start": Start a grace period.
* "cpustart": CPU first notices a grace-period start.
* "cpuqs": CPU passes through a quiescent state.
* "cpuonl": CPU comes online.
* "cpuofl": CPU goes offline.
* "reqwait": GP kthread sleeps waiting for grace-period request.
* "reqwaitsig": GP kthread awakened by signal from reqwait state.
* "fqswait": GP kthread waiting until time to force quiescent states.
* "fqsstart": GP kthread starts forcing quiescent states.
* "fqsend": GP kthread done forcing quiescent states.
* "fqswaitsig": GP kthread awakened by signal from fqswait state.
* "end": End a grace period.
* "cpuend": CPU first notices a grace-period end.
*/
TRACE_EVENT(rcu_grace_period,
@ -160,6 +171,46 @@ TRACE_EVENT(rcu_grace_period_init,
__entry->grplo, __entry->grphi, __entry->qsmask)
);
/*
* Tracepoint for RCU no-CBs CPU callback handoffs. This event is intended
* to assist debugging of these handoffs.
*
* The first argument is the name of the RCU flavor, and the second is
* the number of the offloaded CPU are extracted. The third and final
* argument is a string as follows:
*
* "WakeEmpty": Wake rcuo kthread, first CB to empty list.
* "WakeOvf": Wake rcuo kthread, CB list is huge.
* "WakeNot": Don't wake rcuo kthread.
* "WakeNotPoll": Don't wake rcuo kthread because it is polling.
* "Poll": Start of new polling cycle for rcu_nocb_poll.
* "Sleep": Sleep waiting for CBs for !rcu_nocb_poll.
* "WokeEmpty": rcuo kthread woke to find empty list.
* "WokeNonEmpty": rcuo kthread woke to find non-empty list.
* "WaitQueue": Enqueue partially done, timed wait for it to complete.
* "WokeQueue": Partial enqueue now complete.
*/
TRACE_EVENT(rcu_nocb_wake,
TP_PROTO(const char *rcuname, int cpu, const char *reason),
TP_ARGS(rcuname, cpu, reason),
TP_STRUCT__entry(
__field(const char *, rcuname)
__field(int, cpu)
__field(const char *, reason)
),
TP_fast_assign(
__entry->rcuname = rcuname;
__entry->cpu = cpu;
__entry->reason = reason;
),
TP_printk("%s %d %s", __entry->rcuname, __entry->cpu, __entry->reason)
);
/*
* Tracepoint for tasks blocking within preemptible-RCU read-side
* critical sections. Track the type of RCU (which one day might
@ -540,17 +591,17 @@ TRACE_EVENT(rcu_invoke_kfree_callback,
TRACE_EVENT(rcu_batch_end,
TP_PROTO(const char *rcuname, int callbacks_invoked,
bool cb, bool nr, bool iit, bool risk),
char cb, char nr, char iit, char risk),
TP_ARGS(rcuname, callbacks_invoked, cb, nr, iit, risk),
TP_STRUCT__entry(
__field(const char *, rcuname)
__field(int, callbacks_invoked)
__field(bool, cb)
__field(bool, nr)
__field(bool, iit)
__field(bool, risk)
__field(char, cb)
__field(char, nr)
__field(char, iit)
__field(char, risk)
),
TP_fast_assign(
@ -656,6 +707,7 @@ TRACE_EVENT(rcu_barrier,
#define trace_rcu_future_grace_period(rcuname, gpnum, completed, c, \
level, grplo, grphi, event) \
do { } while (0)
#define trace_rcu_nocb_wake(rcuname, cpu, reason) do { } while (0)
#define trace_rcu_preempt_task(rcuname, pid, gpnum) do { } while (0)
#define trace_rcu_unlock_preempted_task(rcuname, gpnum, pid) do { } while (0)
#define trace_rcu_quiescent_state_report(rcuname, gpnum, mask, qsmask, level, \

2
kernel/rcutiny.c
View File

@ -275,7 +275,7 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp)
if (&rcp->rcucblist == rcp->donetail) {
RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, 0, -1));
RCU_TRACE(trace_rcu_batch_end(rcp->name, 0,
ACCESS_ONCE(rcp->rcucblist),
!!ACCESS_ONCE(rcp->rcucblist),
need_resched(),
is_idle_task(current),
false));

56
kernel/rcutree.c
View File

@ -1326,7 +1326,7 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
}
/*
* Initialize a new grace period.
* Initialize a new grace period. Return 0 if no grace period required.
*/
static int rcu_gp_init(struct rcu_state *rsp)
{
@ -1335,10 +1335,18 @@ static int rcu_gp_init(struct rcu_state *rsp)
rcu_bind_gp_kthread();
raw_spin_lock_irq(&rnp->lock);
if (rsp->gp_flags == 0) {
/* Spurious wakeup, tell caller to go back to sleep. */
raw_spin_unlock_irq(&rnp->lock);
return 0;
}
rsp->gp_flags = 0; /* Clear all flags: New grace period. */
if (rcu_gp_in_progress(rsp)) {
/* Grace period already in progress, don't start another. */
if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) {
/*
* Grace period already in progress, don't start another.
* Not supposed to be able to happen.
*/
raw_spin_unlock_irq(&rnp->lock);
return 0;
}
@ -1481,8 +1489,12 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
rsp->fqs_state = RCU_GP_IDLE;
rdp = this_cpu_ptr(rsp->rda);
rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */
if (cpu_needs_another_gp(rsp, rdp))
if (cpu_needs_another_gp(rsp, rdp)) {
rsp->gp_flags = RCU_GP_FLAG_INIT;
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("newreq"));
}
raw_spin_unlock_irq(&rnp->lock);
}
@ -1492,6 +1504,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
static int __noreturn rcu_gp_kthread(void *arg)
{
int fqs_state;
int gf;
unsigned long j;
int ret;
struct rcu_state *rsp = arg;
@ -1501,14 +1514,19 @@ static int __noreturn rcu_gp_kthread(void *arg)
/* Handle grace-period start. */
for (;;) {
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("reqwait"));
wait_event_interruptible(rsp->gp_wq,
rsp->gp_flags &
ACCESS_ONCE(rsp->gp_flags) &
RCU_GP_FLAG_INIT);
if ((rsp->gp_flags & RCU_GP_FLAG_INIT) &&
rcu_gp_init(rsp))
if (rcu_gp_init(rsp))
break;
cond_resched();
flush_signals(current);
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("reqwaitsig"));
}
/* Handle quiescent-state forcing. */
@ -1518,10 +1536,16 @@ static int __noreturn rcu_gp_kthread(void *arg)
j = HZ;
jiffies_till_first_fqs = HZ;
}
ret = 0;
for (;;) {
rsp->jiffies_force_qs = jiffies + j;
if (!ret)
rsp->jiffies_force_qs = jiffies + j;
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("fqswait"));
ret = wait_event_interruptible_timeout(rsp->gp_wq,
(rsp->gp_flags & RCU_GP_FLAG_FQS) ||
((gf = ACCESS_ONCE(rsp->gp_flags)) &
RCU_GP_FLAG_FQS) ||
(!ACCESS_ONCE(rnp->qsmask) &&
!rcu_preempt_blocked_readers_cgp(rnp)),
j);
@ -1530,13 +1554,23 @@ static int __noreturn rcu_gp_kthread(void *arg)
!rcu_preempt_blocked_readers_cgp(rnp))
break;
/* If time for quiescent-state forcing, do it. */
if (ret == 0 || (rsp->gp_flags & RCU_GP_FLAG_FQS)) {
if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) ||
(gf & RCU_GP_FLAG_FQS)) {
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("fqsstart"));
fqs_state = rcu_gp_fqs(rsp, fqs_state);
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("fqsend"));
cond_resched();
} else {
/* Deal with stray signal. */
cond_resched();
flush_signals(current);
trace_rcu_grace_period(rsp->name,
ACCESS_ONCE(rsp->gpnum),
TPS("fqswaitsig"));
}
j = jiffies_till_next_fqs;
if (j > HZ) {
@ -1584,6 +1618,8 @@ rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp,
return;
}
rsp->gp_flags = RCU_GP_FLAG_INIT;
trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum),
TPS("newreq"));
/*
* We can't do wakeups while holding the rnp->lock, as that

35
kernel/rcutree_plugin.h
View File

@ -2113,15 +2113,22 @@ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp,
/* If we are not being polled and there is a kthread, awaken it ... */
t = ACCESS_ONCE(rdp->nocb_kthread);
if (rcu_nocb_poll || !t)
if (rcu_nocb_poll || !t) {
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
TPS("WakeNotPoll"));
return;
}
len = atomic_long_read(&rdp->nocb_q_count);
if (old_rhpp == &rdp->nocb_head) {
wake_up(&rdp->nocb_wq); /* ... only if queue was empty ... */
rdp->qlen_last_fqs_check = 0;
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeEmpty"));
} else if (len > rdp->qlen_last_fqs_check + qhimark) {
wake_up_process(t); /* ... or if many callbacks queued. */
rdp->qlen_last_fqs_check = LONG_MAX / 2;
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeOvf"));
} else {
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot"));
}
return;
}
@ -2145,10 +2152,12 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp,
if (__is_kfree_rcu_offset((unsigned long)rhp->func))
trace_rcu_kfree_callback(rdp->rsp->name, rhp,
(unsigned long)rhp->func,
rdp->qlen_lazy, rdp->qlen);
-atomic_long_read(&rdp->nocb_q_count_lazy),
-atomic_long_read(&rdp->nocb_q_count));
else
trace_rcu_callback(rdp->rsp->name, rhp,
rdp->qlen_lazy, rdp->qlen);
-atomic_long_read(&rdp->nocb_q_count_lazy),
-atomic_long_read(&rdp->nocb_q_count));
return 1;
}
@ -2226,6 +2235,7 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp)
static int rcu_nocb_kthread(void *arg)
{
int c, cl;
bool firsttime = 1;
struct rcu_head *list;
struct rcu_head *next;
struct rcu_head **tail;
@ -2234,14 +2244,27 @@ static int rcu_nocb_kthread(void *arg)
/* Each pass through this loop invokes one batch of callbacks */
for (;;) {
/* If not polling, wait for next batch of callbacks. */
if (!rcu_nocb_poll)
if (!rcu_nocb_poll) {
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
TPS("Sleep"));
wait_event_interruptible(rdp->nocb_wq, rdp->nocb_head);
} else if (firsttime) {
firsttime = 0;
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
TPS("Poll"));
}
list = ACCESS_ONCE(rdp->nocb_head);
if (!list) {
if (!rcu_nocb_poll)
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
TPS("WokeEmpty"));
schedule_timeout_interruptible(1);
flush_signals(current);
continue;
}
firsttime = 1;
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
TPS("WokeNonEmpty"));
/*
* Extract queued callbacks, update counts, and wait
@ -2262,7 +2285,11 @@ static int rcu_nocb_kthread(void *arg)
next = list->next;
/* Wait for enqueuing to complete, if needed. */
while (next == NULL && &list->next != tail) {
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
TPS("WaitQueue"));
schedule_timeout_interruptible(1);
trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu,
TPS("WokeQueue"));
next = list->next;
}
debug_rcu_head_unqueue(list);