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rcu: Create and use an rcu_rdp_cpu_online()

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The pattern "rdp->grpmask & rcu_rnp_online_cpus(rnp)" occurs frequently
in RCU code in order to determine whether rdp->cpu is online from an
RCU perspective.  This commit therefore creates an rcu_rdp_cpu_online()
function to replace it.

[ paulmck: Apply kernel test robot unused-variable feedback. ]

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2021-12-10 13:44:17 -08:00
parent 80b3fd474c
commit 5ae0f1b58b
2 changed files with 15 additions and 12 deletions
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21
kernel/rcu/tree.c
View File

@ -222,6 +222,16 @@ static unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp)
return READ_ONCE(rnp->qsmaskinitnext);
}
/*
* Is the CPU corresponding to the specified rcu_data structure online
* from RCU's perspective? This perspective is given by that structure's
* ->qsmaskinitnext field rather than by the global cpu_online_mask.
*/
static bool rcu_rdp_cpu_online(struct rcu_data *rdp)
{
return !!(rdp->grpmask & rcu_rnp_online_cpus(rdp->mynode));
}
/*
* Return true if an RCU grace period is in progress. The READ_ONCE()s
* permit this function to be invoked without holding the root rcu_node
@ -1168,14 +1178,12 @@ void rcu_request_urgent_qs_task(struct task_struct *t)
bool rcu_lockdep_current_cpu_online(void)
{
struct rcu_data *rdp;
struct rcu_node *rnp;
bool ret = false;
if (in_nmi() || !rcu_scheduler_fully_active)
return true;
preempt_disable_notrace();
rdp = this_cpu_ptr(&rcu_data);
rnp = rdp->mynode;
/*
* Strictly, we care here about the case where the current CPU is
* in rcu_cpu_starting() and thus has an excuse for rdp->grpmask
@ -1183,8 +1191,7 @@ bool rcu_lockdep_current_cpu_online(void)
* false positive if it's held by some *other* CPU, but that's
* OK because that just means a false *negative* on the warning.
*/
if (rdp->grpmask & rcu_rnp_online_cpus(rnp) ||
arch_spin_is_locked(&rcu_state.ofl_lock))
if (rcu_rdp_cpu_online(rdp) || arch_spin_is_locked(&rcu_state.ofl_lock))
ret = true;
preempt_enable_notrace();
return ret;
@ -1269,8 +1276,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
* For more detail, please refer to the "Hotplug CPU" section
* of RCU's Requirements documentation.
*/
if (WARN_ON_ONCE(!(rdp->grpmask & rcu_rnp_online_cpus(rnp)))) {
bool onl;
if (WARN_ON_ONCE(!rcu_rdp_cpu_online(rdp))) {
struct rcu_node *rnp1;
pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n",
@ -1279,9 +1285,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent)
pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx ->rcu_gp_init_mask %#lx\n",
__func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask);
onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp));
pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n",
__func__, rdp->cpu, ".o"[onl],
__func__, rdp->cpu, ".o"[rcu_rdp_cpu_online(rdp)],
(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags,
(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags);
return 1; /* Break things loose after complaining. */

6
kernel/rcu/tree_plugin.h
View File

@ -330,7 +330,7 @@ void rcu_note_context_switch(bool preempt)
* then queue the task as required based on the states
* of any ongoing and expedited grace periods.
*/
WARN_ON_ONCE((rdp->grpmask & rcu_rnp_online_cpus(rnp)) == 0);
WARN_ON_ONCE(!rcu_rdp_cpu_online(rdp));
WARN_ON_ONCE(!list_empty(&t->rcu_node_entry));
trace_rcu_preempt_task(rcu_state.name,
t->pid,
@ -773,7 +773,6 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
int cpu;
int i;
struct list_head *lhp;
bool onl;
struct rcu_data *rdp;
struct rcu_node *rnp1;
@ -797,9 +796,8 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
pr_cont("\n");
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) {
rdp = per_cpu_ptr(&rcu_data, cpu);
onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp));
pr_info("\t%d: %c online: %ld(%d) offline: %ld(%d)\n",
cpu, ".o"[onl],
cpu, ".o"[rcu_rdp_cpu_online(rdp)],
(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags,
(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags);
}