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rcu: Move RCU's grace-period-change code to ->gp_seq 

This commit moves __note_gp_changes(), note_gp_changes(), and
__rcu_pending() to ->gp_seq, creating new rcu_seq_completed_gp() and
rcu_seq_new_gp() functions for this purpose.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Reinstate "cpuend: trace as suggested by Joel Fernandes. ]
This commit is contained in:
Paul E. McKenney 2018-04-27 16:01:46 -07:00
parent e4be81a2ed
commit 67e14c1e39
2 changed files with 33 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
kernel/rcu/rcu.h
View File

@ -116,6 +116,23 @@ static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
return ULONG_CMP_GE(READ_ONCE(*sp), s);
}
/*
* Has a grace period completed since the time the old gp_seq was collected?
*/
static inline bool rcu_seq_completed_gp(unsigned long old, unsigned long new)
{
return ULONG_CMP_LT(old, new & ~RCU_SEQ_STATE_MASK);
}
/*
* Has a grace period started since the time the old gp_seq was collected?
*/
static inline bool rcu_seq_new_gp(unsigned long old, unsigned long new)
{
return ULONG_CMP_LT((old + RCU_SEQ_STATE_MASK) & ~RCU_SEQ_STATE_MASK,
new);
}
/*
* debug_rcu_head_queue()/debug_rcu_head_unqueue() are used internally
* by call_rcu() and rcu callback execution, and are therefore not part of the

39
kernel/rcu/tree.c
View File

@ -1790,24 +1790,23 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
raw_lockdep_assert_held_rcu_node(rnp);
if (rdp->gp_seq == rnp->gp_seq)
return false; /* Nothing to do. */
/* Handle the ends of any preceding grace periods first. */
if (rdp->completed == rnp->completed &&
!unlikely(READ_ONCE(rdp->gpwrap))) {
/* No grace period end, so just accelerate recent callbacks. */
ret = rcu_accelerate_cbs(rsp, rnp, rdp);
} else {
/* Advance callbacks. */
ret = rcu_advance_cbs(rsp, rnp, rdp);
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->gpnum, TPS("cpuend"));
trace_rcu_grace_period(rsp->name, rdp->gp_seq, TPS("cpuend"));
} else {
ret = rcu_accelerate_cbs(rsp, rnp, rdp); /* Recent callbacks. */
}
if (rdp->gpnum != rnp->gpnum || unlikely(READ_ONCE(rdp->gpwrap))) {
/* Now handle the beginnings of any new-to-this-CPU grace periods. */
if (rcu_seq_new_gp(rdp->gp_seq, rnp->gp_seq) ||
unlikely(READ_ONCE(rdp->gpwrap))) {
/*
* If the current grace period is waiting for this CPU,
* set up to detect a quiescent state, otherwise don't
@ -1823,8 +1822,7 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp,
WRITE_ONCE(rdp->gpwrap, false);
rcu_gpnum_ovf(rnp, rdp);
}
if (rdp->gp_seq != rnp->gp_seq)
rdp->gp_seq = rnp->gp_seq;
rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */
return ret;
}
@ -1836,8 +1834,7 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp)
local_irq_save(flags);
rnp = rdp->mynode;
if ((rdp->gpnum == READ_ONCE(rnp->gpnum) &&
rdp->completed == READ_ONCE(rnp->completed) &&
if ((rdp->gp_seq == rcu_seq_current(&rnp->gp_seq) &&
!unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */
!raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */
local_irq_restore(flags);
@ -3286,12 +3283,8 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
return 1;
/* Has another RCU grace period completed? */
if (READ_ONCE(rnp->completed) != rdp->completed) /* outside lock */
return 1;
/* Has a new RCU grace period started? */
if (READ_ONCE(rnp->gpnum) != rdp->gpnum ||
/* Have RCU grace period completed or started? */
if (rcu_seq_current(&rnp->gp_seq) != rdp->gp_seq ||
unlikely(READ_ONCE(rdp->gpwrap))) /* outside lock */
return 1;