rcu: Remove ->gpnum and ->completed

Now that everything has been converted to use ->gp_seq instead of
->gpnum and ->completed, this commit removes ->gpnum and ->completed.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 42e89d4..0aeddc9 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -95,8 +95,6 @@ struct rcu_state sname##_state = { \
        .rda = &sname##_data, \
        .call = cr, \
        .gp_state = RCU_GP_IDLE, \
-       .gpnum = 0UL - 300UL, \
-       .completed = 0UL - 300UL, \
        .gp_seq = (0UL - 300UL) << RCU_SEQ_CTR_SHIFT, \
        .barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
        .name = RCU_STATE_NAME(sname), \
@@ -1349,8 +1347,6 @@ static void print_other_cpu_stall(struct rcu_state *rsp, unsigned long gp_seq)
        struct rcu_node *rnp = rcu_get_root(rsp);
        long totqlen = 0;
 
-       WARN_ON_ONCE(gp_seq & 0x2); /* Remove when ->gpnum removed. */
-
        /* Kick and suppress, if so configured. */
        rcu_stall_kick_kthreads(rsp);
        if (rcu_cpu_stall_suppress)
@@ -1582,8 +1578,6 @@ static bool rcu_start_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
         * not be released.
         */
        raw_lockdep_assert_held_rcu_node(rnp);
-       WARN_ON_ONCE(c & 0x2); /* Catch any lingering use of ->gpnum. */
-       WARN_ON_ONCE(((rnp->completed << RCU_SEQ_CTR_SHIFT) >> RCU_SEQ_CTR_SHIFT) != rcu_seq_ctr(rnp->gp_seq)); /* Catch any ->completed/->gp_seq mismatches. */
        trace_rcu_this_gp(rnp, rdp, c, TPS("Startleaf"));
        for (rnp_root = rnp; 1; rnp_root = rnp_root->parent) {
                if (rnp_root != rnp)
@@ -1757,8 +1751,6 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
        if (rcu_seq_completed_gp(rdp->gp_seq, rnp->gp_seq) ||
            unlikely(READ_ONCE(rdp->gpwrap))) {
                ret = rcu_advance_cbs(rsp, rnp, rdp); /* Advance callbacks. */
-               /* Remember that we saw this grace-period completion. */
-               rdp->completed = rnp->completed;
                trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("cpuend"));
        } else {
                ret = rcu_accelerate_cbs(rsp, rnp, rdp); /* Recent callbacks. */
@@ -1772,7 +1764,6 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
                 * set up to detect a quiescent state, otherwise don't
                 * go looking for one.
                 */
-               rdp->gpnum = rnp->gpnum;
                trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("cpustart"));
                need_gp = !!(rnp->qsmask & rdp->grpmask);
                rdp->cpu_no_qs.b.norm = need_gp;
@@ -1843,13 +1834,8 @@ static bool rcu_gp_init(struct rcu_state *rsp)
 
        /* Advance to a new grace period and initialize state. */
        record_gp_stall_check_time(rsp);
-       /* Record GP times before starting GP, hence smp_store_release(). */
-       WARN_ON_ONCE(rsp->gpnum << RCU_SEQ_CTR_SHIFT != rsp->gp_seq);
-       smp_store_release(&rsp->gpnum, rsp->gpnum + 1);
-       smp_mb(); /* Pairs with barriers in stall-warning code. */
+       /* Record GP times before starting GP, hence rcu_seq_start(). */
        rcu_seq_start(&rsp->gp_seq);
-       if (WARN_ON_ONCE(((rnp->completed << RCU_SEQ_CTR_SHIFT) >> RCU_SEQ_CTR_SHIFT) != rcu_seq_ctr(rnp->gp_seq))) /* Catch any ->completed/->gp_seq mismatches. */
-               pr_info("%s ->completed: %#lx (%#lx) ->gp_seq %#lx (%#lx)\n", __func__, rnp->completed, (rnp->completed << RCU_SEQ_CTR_SHIFT) >> RCU_SEQ_CTR_SHIFT, rnp->gp_seq, rcu_seq_ctr(rnp->gp_seq));
        trace_rcu_grace_period(rsp->name, rsp->gp_seq, TPS("start"));
        raw_spin_unlock_irq_rcu_node(rnp);
 
@@ -1920,9 +1906,6 @@ static bool rcu_gp_init(struct rcu_state *rsp)
                rdp = this_cpu_ptr(rsp->rda);
                rcu_preempt_check_blocked_tasks(rnp);
                rnp->qsmask = rnp->qsmaskinit;
-               WRITE_ONCE(rnp->gpnum, rsp->gpnum);
-               if (WARN_ON_ONCE(rnp->completed != rsp->completed))
-                       WRITE_ONCE(rnp->completed, rsp->completed);
                WRITE_ONCE(rnp->gp_seq, rsp->gp_seq);
                if (rnp == rdp->mynode)
                        (void)__note_gp_changes(rsp, rnp, rdp);
@@ -2012,13 +1995,13 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
        raw_spin_unlock_irq_rcu_node(rnp);
 
        /*
-        * Propagate new ->completed value to rcu_node structures so
-        * that other CPUs don't have to wait until the start of the next
-        * grace period to process their callbacks.  This also avoids
-        * some nasty RCU grace-period initialization races by forcing
-        * the end of the current grace period to be completely recorded in
-        * all of the rcu_node structures before the beginning of the next
-        * grace period is recorded in any of the rcu_node structures.
+        * Propagate new ->gp_seq value to rcu_node structures so that
+        * other CPUs don't have to wait until the start of the next grace
+        * period to process their callbacks.  This also avoids some nasty
+        * RCU grace-period initialization races by forcing the end of
+        * the current grace period to be completely recorded in all of
+        * the rcu_node structures before the beginning of the next grace
+        * period is recorded in any of the rcu_node structures.
         */
        new_gp_seq = rsp->gp_seq;
        rcu_seq_end(&new_gp_seq);
@@ -2027,7 +2010,6 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
                if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)))
                        dump_blkd_tasks(rnp, 10);
                WARN_ON_ONCE(rnp->qsmask);
-               WRITE_ONCE(rnp->completed, rsp->gpnum);
                WRITE_ONCE(rnp->gp_seq, new_gp_seq);
                rdp = this_cpu_ptr(rsp->rda);
                if (rnp == rdp->mynode)
@@ -2045,7 +2027,6 @@ static void rcu_gp_cleanup(struct rcu_state *rsp)
        raw_spin_lock_irq_rcu_node(rnp); /* GP before rsp->gp_seq update. */
 
        /* Declare grace period done. */
-       WRITE_ONCE(rsp->completed, rsp->gpnum);
        rcu_seq_end(&rsp->gp_seq);
        trace_rcu_grace_period(rsp->name, rsp->gp_seq, TPS("end"));
        rsp->gp_state = RCU_GP_IDLE;
@@ -3496,9 +3477,9 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
 
 /*
  * Initialize a CPU's per-CPU RCU data.  Note that only one online or
- * offline event can be happening at a given time.  Note also that we
- * can accept some slop in the rsp->completed access due to the fact
- * that this CPU cannot possibly have any RCU callbacks in flight yet.
+ * offline event can be happening at a given time.  Note also that we can
+ * accept some slop in the rsp->gp_seq access due to the fact that this
+ * CPU cannot possibly have any RCU callbacks in flight yet.
  */
 static void
 rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
@@ -3527,8 +3508,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
        rnp = rdp->mynode;
        raw_spin_lock_rcu_node(rnp);            /* irqs already disabled. */
        rdp->beenonline = true;  /* We have now been online. */
-       rdp->gpnum = rnp->completed; /* Make CPU later note any new GP. */
-       rdp->completed = rnp->completed;
        rdp->gp_seq = rnp->gp_seq;
        rdp->gp_seq_needed = rnp->gp_seq;
        rdp->cpu_no_qs.b.norm = true;
@@ -3908,8 +3887,6 @@ static void __init rcu_init_one(struct rcu_state *rsp)
                        raw_spin_lock_init(&rnp->fqslock);
                        lockdep_set_class_and_name(&rnp->fqslock,
                                                   &rcu_fqs_class[i], fqs[i]);
-                       rnp->gpnum = rsp->gpnum;
-                       rnp->completed = rsp->completed;
                        rnp->gp_seq = rsp->gp_seq;
                        rnp->gp_seq_needed = rsp->gp_seq;
                        rnp->completedqs = rsp->gp_seq;

diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 9329c1f..3def94f 100644 (file)
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -81,12 +81,6 @@ struct rcu_node {
        raw_spinlock_t __private lock;  /* Root rcu_node's lock protects */
                                        /*  some rcu_state fields as well as */
                                        /*  following. */
-       unsigned long gpnum;    /* Current grace period for this node. */
-                               /*  This will either be equal to or one */
-                               /*  behind the root rcu_node's gpnum. */
-       unsigned long completed; /* Last GP completed for this node. */
-                               /*  This will either be equal to or one */
-                               /*  behind the root rcu_node's gpnum. */
        unsigned long gp_seq;   /* Track rsp->rcu_gp_seq. */
        unsigned long gp_seq_needed; /* Track rsp->rcu_gp_seq_needed. */
        unsigned long completedqs; /* All QSes done for this node. */
@@ -192,10 +186,6 @@ union rcu_noqs {
 /* Per-CPU data for read-copy update. */
 struct rcu_data {
        /* 1) quiescent-state and grace-period handling : */
-       unsigned long   completed;      /* Track rsp->completed gp number */
-                                       /*  in order to detect GP end. */
-       unsigned long   gpnum;          /* Highest gp number that this CPU */
-                                       /*  is aware of having started. */
        unsigned long   gp_seq;         /* Track rsp->rcu_gp_seq counter. */
        unsigned long   gp_seq_needed;  /* Track rsp->rcu_gp_seq_needed ctr. */
        unsigned long   rcu_qs_ctr_snap;/* Snapshot of rcu_qs_ctr to check */
@@ -203,7 +193,7 @@ struct rcu_data {
        union rcu_noqs  cpu_no_qs;      /* No QSes yet for this CPU. */
        bool            core_needs_qs;  /* Core waits for quiesc state. */
        bool            beenonline;     /* CPU online at least once. */
-       bool            gpwrap;         /* Possible gpnum/completed wrap. */
+       bool            gpwrap;         /* Possible ->gp_seq wrap. */
        struct rcu_node *mynode;        /* This CPU's leaf of hierarchy */
        unsigned long grpmask;          /* Mask to apply to leaf qsmask. */
        unsigned long   ticks_this_gp;  /* The number of scheduling-clock */
@@ -328,8 +318,6 @@ struct rcu_state {
 
        u8      boost ____cacheline_internodealigned_in_smp;
                                                /* Subject to priority boost. */
-       unsigned long gpnum;                    /* Current gp number. */
-       unsigned long completed;                /* # of last completed gp. */
        unsigned long gp_seq;                   /* Grace-period sequence #. */
        struct task_struct *gp_kthread;         /* Task for grace periods. */
        struct swait_queue_head gp_wq;          /* Where GP task waits. */

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index c8a2c77..3a6e041 100644 (file)
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -690,7 +690,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
  * Check that the list of blocked tasks for the newly completed grace
  * period is in fact empty.  It is a serious bug to complete a grace
  * period that still has RCU readers blocked!  This function must be
- * invoked -before- updating this rnp's ->gpnum, and the rnp's ->lock
+ * invoked -before- updating this rnp's ->gp_seq, and the rnp's ->lock
  * must be held by the caller.
  *
  * Also, if there are blocked tasks on the list, they automatically