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rcutorture: Pull callback forward-progress data into rcu_fwd struct

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Now that RCU behaves reasonably well with the current single-kthread
call_rcu() forward-progress testing, it is time to add more kthreads.
This commit takes a first step towards that goal by wrapping what
will be the per-kthread data into a new rcu_fwd structure.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2019-11-05 08:31:56 -08:00
parent ebfbaa8dcc
commit a289e608b3
1 changed files with 58 additions and 45 deletions
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103
kernel/rcu/rcutorture.c
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@ -1663,23 +1663,34 @@ struct rcu_fwd_cb {
struct rcu_fwd_cb *rfc_next;
int rfc_gps;
};
static DEFINE_SPINLOCK(rcu_fwd_lock);
static struct rcu_fwd_cb *rcu_fwd_cb_head;
static struct rcu_fwd_cb **rcu_fwd_cb_tail = &rcu_fwd_cb_head;
static long n_launders_cb;
static unsigned long rcu_fwd_startat;
static bool rcu_fwd_emergency_stop;
#define MAX_FWD_CB_JIFFIES (8 * HZ) /* Maximum CB test duration. */
#define MIN_FWD_CB_LAUNDERS 3 /* This many CB invocations to count. */
#define MIN_FWD_CBS_LAUNDERED 100 /* Number of counted CBs. */
#define FWD_CBS_HIST_DIV 10 /* Histogram buckets/second. */
#define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV))
struct rcu_launder_hist {
long n_launders;
unsigned long launder_gp_seq;
};
#define N_LAUNDERS_HIST (2 * MAX_FWD_CB_JIFFIES / (HZ / FWD_CBS_HIST_DIV))
static struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST];
static unsigned long rcu_launder_gp_seq_start;
struct rcu_fwd {
spinlock_t rcu_fwd_lock;
struct rcu_fwd_cb *rcu_fwd_cb_head;
struct rcu_fwd_cb **rcu_fwd_cb_tail;
long n_launders_cb;
unsigned long rcu_fwd_startat;
struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST];
unsigned long rcu_launder_gp_seq_start;
};
struct rcu_fwd rcu_fwds = {
.rcu_fwd_lock = __SPIN_LOCK_UNLOCKED(rcu_fwds.rcu_fwd_lock),
.rcu_fwd_cb_tail = &rcu_fwds.rcu_fwd_cb_head,
};
bool rcu_fwd_emergency_stop;
static void rcu_torture_fwd_cb_hist(void)
{
@ -1688,16 +1699,17 @@ static void rcu_torture_fwd_cb_hist(void)
int i;
int j;
for (i = ARRAY_SIZE(n_launders_hist) - 1; i > 0; i--)
if (n_launders_hist[i].n_launders > 0)
for (i = ARRAY_SIZE(rcu_fwds.n_launders_hist) - 1; i > 0; i--)
if (rcu_fwds.n_launders_hist[i].n_launders > 0)
break;
pr_alert("%s: Callback-invocation histogram (duration %lu jiffies):",
__func__, jiffies - rcu_fwd_startat);
gps_old = rcu_launder_gp_seq_start;
__func__, jiffies - rcu_fwds.rcu_fwd_startat);
gps_old = rcu_fwds.rcu_launder_gp_seq_start;
for (j = 0; j <= i; j++) {
gps = n_launders_hist[j].launder_gp_seq;
gps = rcu_fwds.n_launders_hist[j].launder_gp_seq;
pr_cont(" %ds/%d: %ld:%ld",
j + 1, FWD_CBS_HIST_DIV, n_launders_hist[j].n_launders,
j + 1, FWD_CBS_HIST_DIV,
rcu_fwds.n_launders_hist[j].n_launders,
rcutorture_seq_diff(gps, gps_old));
gps_old = gps;
}
@ -1714,17 +1726,17 @@ static void rcu_torture_fwd_cb_cr(struct rcu_head *rhp)
rfcp->rfc_next = NULL;
rfcp->rfc_gps++;
spin_lock_irqsave(&rcu_fwd_lock, flags);
rfcpp = rcu_fwd_cb_tail;
rcu_fwd_cb_tail = &rfcp->rfc_next;
spin_lock_irqsave(&rcu_fwds.rcu_fwd_lock, flags);
rfcpp = rcu_fwds.rcu_fwd_cb_tail;
rcu_fwds.rcu_fwd_cb_tail = &rfcp->rfc_next;
WRITE_ONCE(*rfcpp, rfcp);
WRITE_ONCE(n_launders_cb, n_launders_cb + 1);
i = ((jiffies - rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV));
if (i >= ARRAY_SIZE(n_launders_hist))
i = ARRAY_SIZE(n_launders_hist) - 1;
n_launders_hist[i].n_launders++;
n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq();
spin_unlock_irqrestore(&rcu_fwd_lock, flags);
WRITE_ONCE(rcu_fwds.n_launders_cb, rcu_fwds.n_launders_cb + 1);
i = ((jiffies - rcu_fwds.rcu_fwd_startat) / (HZ / FWD_CBS_HIST_DIV));
if (i >= ARRAY_SIZE(rcu_fwds.n_launders_hist))
i = ARRAY_SIZE(rcu_fwds.n_launders_hist) - 1;
rcu_fwds.n_launders_hist[i].n_launders++;
rcu_fwds.n_launders_hist[i].launder_gp_seq = cur_ops->get_gp_seq();
spin_unlock_irqrestore(&rcu_fwds.rcu_fwd_lock, flags);
}
// Give the scheduler a chance, even on nohz_full CPUs.
@ -1751,16 +1763,16 @@ static unsigned long rcu_torture_fwd_prog_cbfree(void)
struct rcu_fwd_cb *rfcp;
for (;;) {
spin_lock_irqsave(&rcu_fwd_lock, flags);
rfcp = rcu_fwd_cb_head;
spin_lock_irqsave(&rcu_fwds.rcu_fwd_lock, flags);
rfcp = rcu_fwds.rcu_fwd_cb_head;
if (!rfcp) {
spin_unlock_irqrestore(&rcu_fwd_lock, flags);
spin_unlock_irqrestore(&rcu_fwds.rcu_fwd_lock, flags);
break;
}
rcu_fwd_cb_head = rfcp->rfc_next;
if (!rcu_fwd_cb_head)
rcu_fwd_cb_tail = &rcu_fwd_cb_head;
spin_unlock_irqrestore(&rcu_fwd_lock, flags);
rcu_fwds.rcu_fwd_cb_head = rfcp->rfc_next;
if (!rcu_fwds.rcu_fwd_cb_head)
rcu_fwds.rcu_fwd_cb_tail = &rcu_fwds.rcu_fwd_cb_head;
spin_unlock_irqrestore(&rcu_fwds.rcu_fwd_lock, flags);
kfree(rfcp);
freed++;
rcu_torture_fwd_prog_cond_resched(freed);
@ -1804,8 +1816,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries)
sd = cur_ops->stall_dur() + 1;
sd4 = (sd + fwd_progress_div - 1) / fwd_progress_div;
dur = sd4 + torture_random(&trs) % (sd - sd4);
WRITE_ONCE(rcu_fwd_startat, jiffies);
stopat = rcu_fwd_startat + dur;
WRITE_ONCE(rcu_fwds.rcu_fwd_startat, jiffies);
stopat = rcu_fwds.rcu_fwd_startat + dur;
while (time_before(jiffies, stopat) &&
!shutdown_time_arrived() &&
!READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
@ -1864,23 +1876,23 @@ static void rcu_torture_fwd_prog_cr(void)
/* Loop continuously posting RCU callbacks. */
WRITE_ONCE(rcu_fwd_cb_nodelay, true);
cur_ops->sync(); /* Later readers see above write. */
WRITE_ONCE(rcu_fwd_startat, jiffies);
stopat = rcu_fwd_startat + MAX_FWD_CB_JIFFIES;
WRITE_ONCE(rcu_fwds.rcu_fwd_startat, jiffies);
stopat = rcu_fwds.rcu_fwd_startat + MAX_FWD_CB_JIFFIES;
n_launders = 0;
n_launders_cb = 0;
rcu_fwds.n_launders_cb = 0; // Hoist initialization for multi-kthread
n_launders_sa = 0;
n_max_cbs = 0;
n_max_gps = 0;
for (i = 0; i < ARRAY_SIZE(n_launders_hist); i++)
n_launders_hist[i].n_launders = 0;
for (i = 0; i < ARRAY_SIZE(rcu_fwds.n_launders_hist); i++)
rcu_fwds.n_launders_hist[i].n_launders = 0;
cver = READ_ONCE(rcu_torture_current_version);
gps = cur_ops->get_gp_seq();
rcu_launder_gp_seq_start = gps;
rcu_fwds.rcu_launder_gp_seq_start = gps;
tick_dep_set_task(current, TICK_DEP_BIT_RCU);
while (time_before(jiffies, stopat) &&
!shutdown_time_arrived() &&
!READ_ONCE(rcu_fwd_emergency_stop) && !torture_must_stop()) {
rfcp = READ_ONCE(rcu_fwd_cb_head);
rfcp = READ_ONCE(rcu_fwds.rcu_fwd_cb_head);
rfcpn = NULL;
if (rfcp)
rfcpn = READ_ONCE(rfcp->rfc_next);
@ -1888,7 +1900,7 @@ static void rcu_torture_fwd_prog_cr(void)
if (rfcp->rfc_gps >= MIN_FWD_CB_LAUNDERS &&
++n_max_gps >= MIN_FWD_CBS_LAUNDERED)
break;
rcu_fwd_cb_head = rfcpn;
rcu_fwds.rcu_fwd_cb_head = rfcpn;
n_launders++;
n_launders_sa++;
} else {
@ -1910,7 +1922,7 @@ static void rcu_torture_fwd_prog_cr(void)
}
}
stoppedat = jiffies;
n_launders_cb_snap = READ_ONCE(n_launders_cb);
n_launders_cb_snap = READ_ONCE(rcu_fwds.n_launders_cb);
cver = READ_ONCE(rcu_torture_current_version) - cver;
gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
@ -1921,7 +1933,8 @@ static void rcu_torture_fwd_prog_cr(void)
WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED);
pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n",
__func__,
stoppedat - rcu_fwd_startat, jiffies - stoppedat,
stoppedat - rcu_fwds.rcu_fwd_startat,
jiffies - stoppedat,
n_launders + n_max_cbs - n_launders_cb_snap,
n_launders, n_launders_sa,
n_max_gps, n_max_cbs, cver, gps);
@ -1943,7 +1956,7 @@ static int rcutorture_oom_notify(struct notifier_block *self,
WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
__func__);
rcu_torture_fwd_cb_hist();
rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rcu_fwd_startat)) / 2);
rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rcu_fwds.rcu_fwd_startat)) / 2);
WRITE_ONCE(rcu_fwd_emergency_stop, true);
smp_mb(); /* Emergency stop before free and wait to avoid hangs. */
pr_info("%s: Freed %lu RCU callbacks.\n",