diff options
| -rw-r--r-- | include/trace/events/rcu.h | 10 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 46 |
2 files changed, 39 insertions, 17 deletions
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 9d4f9b3a2b7b..e3facb356838 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -385,11 +385,11 @@ TRACE_EVENT(rcu_quiescent_state_report, /* * Tracepoint for quiescent states detected by force_quiescent_state(). - * These trace events include the type of RCU, the grace-period number - * that was blocked by the CPU, the CPU itself, and the type of quiescent - * state, which can be "dti" for dyntick-idle mode, "ofl" for CPU offline, - * or "kick" when kicking a CPU that has been in dyntick-idle mode for - * too long. + * These trace events include the type of RCU, the grace-period number that + * was blocked by the CPU, the CPU itself, and the type of quiescent state, + * which can be "dti" for dyntick-idle mode, "ofl" for CPU offline, "kick" + * when kicking a CPU that has been in dyntick-idle mode for too long, or + * "rqc" if the CPU got a quiescent state via its rcu_qs_ctr. */ TRACE_EVENT(rcu_fqs, diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 8b970319c75b..d8245cbd08f9 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1232,7 +1232,10 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp, static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, bool *isidle, unsigned long *maxj) { + unsigned long jtsq; int *rcrmp; + unsigned long rjtsc; + struct rcu_node *rnp; /* * If the CPU passed through or entered a dynticks idle phase with @@ -1248,6 +1251,31 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, return 1; } + /* Compute and saturate jiffies_till_sched_qs. */ + jtsq = jiffies_till_sched_qs; + rjtsc = rcu_jiffies_till_stall_check(); + if (jtsq > rjtsc / 2) { + WRITE_ONCE(jiffies_till_sched_qs, rjtsc); + jtsq = rjtsc / 2; + } else if (jtsq < 1) { + WRITE_ONCE(jiffies_till_sched_qs, 1); + jtsq = 1; + } + + /* + * Has this CPU encountered a cond_resched_rcu_qs() since the + * beginning of the grace period? For this to be the case, + * the CPU has to have noticed the current grace period. This + * might not be the case for nohz_full CPUs looping in the kernel. + */ + rnp = rdp->mynode; + if (time_after(jiffies, rdp->rsp->gp_start + jtsq) && + READ_ONCE(rdp->rcu_qs_ctr_snap) != per_cpu(rcu_qs_ctr, rdp->cpu) && + READ_ONCE(rdp->gpnum) == rnp->gpnum && !rdp->gpwrap) { + trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("rqc")); + return 1; + } + /* * Check for the CPU being offline, but only if the grace period * is old enough. We don't need to worry about the CPU changing @@ -1290,9 +1318,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, * warning delay. */ rcrmp = &per_cpu(rcu_sched_qs_mask, rdp->cpu); - if (ULONG_CMP_GE(jiffies, - rdp->rsp->gp_start + jiffies_till_sched_qs) || - ULONG_CMP_GE(jiffies, rdp->rsp->jiffies_resched)) { + if (time_after(jiffies, rdp->rsp->gp_start + jtsq) || + time_after(jiffies, rdp->rsp->jiffies_resched)) { if (!(READ_ONCE(*rcrmp) & rdp->rsp->flavor_mask)) { WRITE_ONCE(rdp->cond_resched_completed, READ_ONCE(rdp->mynode->completed)); @@ -2550,10 +2577,8 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) rnp = rdp->mynode; raw_spin_lock_irqsave_rcu_node(rnp, flags); - if ((rdp->cpu_no_qs.b.norm && - rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) || - rdp->gpnum != rnp->gpnum || rnp->completed == rnp->gpnum || - rdp->gpwrap) { + if (rdp->cpu_no_qs.b.norm || rdp->gpnum != rnp->gpnum || + rnp->completed == rnp->gpnum || rdp->gpwrap) { /* * The grace period in which this quiescent state was @@ -2608,8 +2633,7 @@ rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) * Was there a quiescent state since the beginning of the grace * period? If no, then exit and wait for the next call. */ - if (rdp->cpu_no_qs.b.norm && - rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) + if (rdp->cpu_no_qs.b.norm) return; /* @@ -3563,9 +3587,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) rdp->core_needs_qs && rdp->cpu_no_qs.b.norm && rdp->rcu_qs_ctr_snap == __this_cpu_read(rcu_qs_ctr)) { rdp->n_rp_core_needs_qs++; - } else if (rdp->core_needs_qs && - (!rdp->cpu_no_qs.b.norm || - rdp->rcu_qs_ctr_snap != __this_cpu_read(rcu_qs_ctr))) { + } else if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm) { rdp->n_rp_report_qs++; return 1; } |