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rcu: Remove ->gpnum and ->completed

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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>
This commit is contained in:
Paul E. McKenney 2018-05-01 14:34:08 -07:00
parent fee5997c17
commit ff3bb6f4d0
3 changed files with 13 additions and 48 deletions
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45
kernel/rcu/tree.c
View File

@ -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;

14
kernel/rcu/tree.h
View File

@ -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. */

2
kernel/rcu/tree_plugin.h
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@ -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