rcutorture: Pull callback forward-progress data into rcu_fwd struct

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>

diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index dee043f..22a75a4 100644 (file)
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -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",