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rcu: Convert ->rcu_iw_gpnum to ->gp_seq 

This commit switches the interrupt-disabled detection mechanism to
->gp_seq.  This mechanism is used as part of RCU CPU stall warnings,
and detects cases where the stall is due to a CPU having interrupts
disabled.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-04-28 14:15:40 -07:00
parent ba04107fc9
commit 8aa670cdac
3 changed files with 8 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
kernel/rcu/tree.c
View File

@ -1099,8 +1099,8 @@ static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp)
if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + ULONG_MAX / 4,
rnp->gp_seq))
WRITE_ONCE(rdp->gpwrap, true);
if (ULONG_CMP_LT(rdp->rcu_iw_gpnum + ULONG_MAX / 4, rnp->gpnum))
rdp->rcu_iw_gpnum = rnp->gpnum + ULONG_MAX / 4;
if (ULONG_CMP_LT(rdp->rcu_iw_gp_seq + ULONG_MAX / 4, rnp->gp_seq))
rdp->rcu_iw_gp_seq = rnp->gp_seq + ULONG_MAX / 4;
}
/*
@ -1134,7 +1134,7 @@ static void rcu_iw_handler(struct irq_work *iwp)
rnp = rdp->mynode;
raw_spin_lock_rcu_node(rnp);
if (!WARN_ON_ONCE(!rdp->rcu_iw_pending)) {
rdp->rcu_iw_gpnum = rnp->gpnum;
rdp->rcu_iw_gp_seq = rnp->gp_seq;
rdp->rcu_iw_pending = false;
}
raw_spin_unlock_rcu_node(rnp);
@ -1231,11 +1231,11 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
if (jiffies - rdp->rsp->gp_start > rcu_jiffies_till_stall_check() / 2) {
resched_cpu(rdp->cpu);
if (IS_ENABLED(CONFIG_IRQ_WORK) &&
!rdp->rcu_iw_pending && rdp->rcu_iw_gpnum != rnp->gpnum &&
!rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq &&
(rnp->ffmask & rdp->grpmask)) {
init_irq_work(&rdp->rcu_iw, rcu_iw_handler);
rdp->rcu_iw_pending = true;
rdp->rcu_iw_gpnum = rnp->gpnum;
rdp->rcu_iw_gp_seq = rnp->gp_seq;
irq_work_queue_on(&rdp->rcu_iw, rdp->cpu);
}
}
@ -3575,7 +3575,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp)
rdp->rcu_qs_ctr_snap = per_cpu(rcu_dynticks.rcu_qs_ctr, cpu);
rdp->core_needs_qs = false;
rdp->rcu_iw_pending = false;
rdp->rcu_iw_gpnum = rnp->gpnum - 1;
rdp->rcu_iw_gp_seq = rnp->gp_seq - 1;
trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}

2
kernel/rcu/tree.h
View File

@ -286,7 +286,7 @@ struct rcu_data {
/* ->rcu_iw* fields protected by leaf rcu_node ->lock. */
struct irq_work rcu_iw; /* Check for non-irq activity. */
bool rcu_iw_pending; /* Is ->rcu_iw pending? */
unsigned long rcu_iw_gpnum; /* ->gpnum associated with ->rcu_iw. */
unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */
int cpu;
struct rcu_state *rsp;

2
kernel/rcu/tree_plugin.h
View File

@ -1763,7 +1763,7 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu)
ticks_value = rsp->gpnum - rdp->gpnum;
}
print_cpu_stall_fast_no_hz(fast_no_hz, cpu);
delta = rdp->mynode->gpnum - rdp->rcu_iw_gpnum;
delta = rcu_seq_ctr(rdp->mynode->gp_seq - rdp->rcu_iw_gp_seq);
pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%03x/%ld/%ld softirq=%u/%u fqs=%ld %s\n",
cpu,
"O."[!!cpu_online(cpu)],