X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=kernel%2Frcu%2Ftree.c;h=1b70cb6fbe3ccda0466f3f0004865d82cdd9399d;hb=99eef8e9369abe009006b4fa7f6ca5086c09cf46;hp=625d0b0cd75a0a2227a3519d781b66ff02ab5523;hpb=862f9f840d32d7656dd7d25dc5c3c67b8244b3e0;p=firefly-linux-kernel-4.4.55.git diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 625d0b0cd75a..1b70cb6fbe3c 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1013,10 +1013,7 @@ static void record_gp_stall_check_time(struct rcu_state *rsp) } /* - * Dump stacks of all tasks running on stalled CPUs. This is a fallback - * for architectures that do not implement trigger_all_cpu_backtrace(). - * The NMI-triggered stack traces are more accurate because they are - * printed by the target CPU. + * Dump stacks of all tasks running on stalled CPUs. */ static void rcu_dump_cpu_stacks(struct rcu_state *rsp) { @@ -1094,7 +1091,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp) (long)rsp->gpnum, (long)rsp->completed, totqlen); if (ndetected == 0) pr_err("INFO: Stall ended before state dump start\n"); - else if (!trigger_all_cpu_backtrace()) + else rcu_dump_cpu_stacks(rsp); /* Complain about tasks blocking the grace period. */ @@ -1125,8 +1122,7 @@ static void print_cpu_stall(struct rcu_state *rsp) pr_cont(" (t=%lu jiffies g=%ld c=%ld q=%lu)\n", jiffies - rsp->gp_start, (long)rsp->gpnum, (long)rsp->completed, totqlen); - if (!trigger_all_cpu_backtrace()) - dump_stack(); + rcu_dump_cpu_stacks(rsp); raw_spin_lock_irqsave(&rnp->lock, flags); if (ULONG_CMP_GE(jiffies, ACCESS_ONCE(rsp->jiffies_stall))) @@ -1305,10 +1301,16 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, * believe that a grace period is in progress, then we must wait * for the one following, which is in "c". Because our request * will be noticed at the end of the current grace period, we don't - * need to explicitly start one. + * need to explicitly start one. We only do the lockless check + * of rnp_root's fields if the current rcu_node structure thinks + * there is no grace period in flight, and because we hold rnp->lock, + * the only possible change is when rnp_root's two fields are + * equal, in which case rnp_root->gpnum might be concurrently + * incremented. But that is OK, as it will just result in our + * doing some extra useless work. */ if (rnp->gpnum != rnp->completed || - ACCESS_ONCE(rnp->gpnum) != ACCESS_ONCE(rnp->completed)) { + ACCESS_ONCE(rnp_root->gpnum) != ACCESS_ONCE(rnp_root->completed)) { rnp->need_future_gp[c & 0x1]++; trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf")); goto out; @@ -1645,11 +1647,6 @@ static int rcu_gp_init(struct rcu_state *rsp) rnp->level, rnp->grplo, rnp->grphi, rnp->qsmask); raw_spin_unlock_irq(&rnp->lock); -#ifdef CONFIG_PROVE_RCU_DELAY - if ((prandom_u32() % (rcu_num_nodes + 1)) == 0 && - system_state == SYSTEM_RUNNING) - udelay(200); -#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */ cond_resched(); } @@ -2347,7 +2344,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) } smp_mb(); /* List handling before counting for rcu_barrier(). */ rdp->qlen_lazy -= count_lazy; - ACCESS_ONCE(rdp->qlen) -= count; + ACCESS_ONCE(rdp->qlen) = rdp->qlen - count; rdp->n_cbs_invoked += count; /* Reinstate batch limit if we have worked down the excess. */ @@ -2485,14 +2482,14 @@ static void force_quiescent_state(struct rcu_state *rsp) struct rcu_node *rnp_old = NULL; /* Funnel through hierarchy to reduce memory contention. */ - rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode; + rnp = __this_cpu_read(rsp->rda->mynode); for (; rnp != NULL; rnp = rnp->parent) { ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) || !raw_spin_trylock(&rnp->fqslock); if (rnp_old != NULL) raw_spin_unlock(&rnp_old->fqslock); if (ret) { - ACCESS_ONCE(rsp->n_force_qs_lh)++; + rsp->n_force_qs_lh++; return; } rnp_old = rnp; @@ -2504,7 +2501,7 @@ static void force_quiescent_state(struct rcu_state *rsp) smp_mb__after_unlock_lock(); raw_spin_unlock(&rnp_old->fqslock); if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { - ACCESS_ONCE(rsp->n_force_qs_lh)++; + rsp->n_force_qs_lh++; raw_spin_unlock_irqrestore(&rnp_old->lock, flags); return; /* Someone beat us to it. */ } @@ -2662,7 +2659,7 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), unsigned long flags; struct rcu_data *rdp; - WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */ + WARN_ON_ONCE((unsigned long)head & 0x1); /* Misaligned rcu_head! */ if (debug_rcu_head_queue(head)) { /* Probable double call_rcu(), so leak the callback. */ ACCESS_ONCE(head->func) = rcu_leak_callback; @@ -2693,7 +2690,7 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), local_irq_restore(flags); return; } - ACCESS_ONCE(rdp->qlen)++; + ACCESS_ONCE(rdp->qlen) = rdp->qlen + 1; if (lazy) rdp->qlen_lazy++; else @@ -3257,7 +3254,7 @@ static void _rcu_barrier(struct rcu_state *rsp) * ACCESS_ONCE() to prevent the compiler from speculating * the increment to precede the early-exit check. */ - ACCESS_ONCE(rsp->n_barrier_done)++; + ACCESS_ONCE(rsp->n_barrier_done) = rsp->n_barrier_done + 1; WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1); _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done); smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */ @@ -3307,7 +3304,7 @@ static void _rcu_barrier(struct rcu_state *rsp) /* Increment ->n_barrier_done to prevent duplicate work. */ smp_mb(); /* Keep increment after above mechanism. */ - ACCESS_ONCE(rsp->n_barrier_done)++; + ACCESS_ONCE(rsp->n_barrier_done) = rsp->n_barrier_done + 1; WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0); _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done); smp_mb(); /* Keep increment before caller's subsequent code. */ @@ -3564,14 +3561,16 @@ static void __init rcu_init_levelspread(struct rcu_state *rsp) static void __init rcu_init_one(struct rcu_state *rsp, struct rcu_data __percpu *rda) { - static char *buf[] = { "rcu_node_0", - "rcu_node_1", - "rcu_node_2", - "rcu_node_3" }; /* Match MAX_RCU_LVLS */ - static char *fqs[] = { "rcu_node_fqs_0", - "rcu_node_fqs_1", - "rcu_node_fqs_2", - "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */ + static const char * const buf[] = { + "rcu_node_0", + "rcu_node_1", + "rcu_node_2", + "rcu_node_3" }; /* Match MAX_RCU_LVLS */ + static const char * const fqs[] = { + "rcu_node_fqs_0", + "rcu_node_fqs_1", + "rcu_node_fqs_2", + "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */ static u8 fl_mask = 0x1; int cpustride = 1; int i;