diff options
Diffstat (limited to 'kernel/rcu/tree.c')
| -rw-r--r-- | kernel/rcu/tree.c | 291 |
1 files changed, 0 insertions, 291 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 424d50ccf9e6..001dd05f6e38 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -102,8 +102,6 @@ int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; /* Number of rcu_nodes at specified level. */ int num_rcu_lvl[] = NUM_RCU_LVL_INIT; int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ -/* panic() on RCU Stall sysctl. */ -int sysctl_panic_on_rcu_stall __read_mostly; /* Commandeer a sysrq key to dump RCU's tree. */ static bool sysrq_rcu; module_param(sysrq_rcu, bool, 0444); @@ -1167,295 +1165,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) return 0; } -static void record_gp_stall_check_time(void) -{ - unsigned long j = jiffies; - unsigned long j1; - - rcu_state.gp_start = j; - j1 = rcu_jiffies_till_stall_check(); - /* Record ->gp_start before ->jiffies_stall. */ - smp_store_release(&rcu_state.jiffies_stall, j + j1); /* ^^^ */ - rcu_state.jiffies_resched = j + j1 / 2; - rcu_state.n_force_qs_gpstart = READ_ONCE(rcu_state.n_force_qs); -} - -/* - * Complain about starvation of grace-period kthread. - */ -static void rcu_check_gp_kthread_starvation(void) -{ - struct task_struct *gpk = rcu_state.gp_kthread; - unsigned long j; - - j = jiffies - READ_ONCE(rcu_state.gp_activity); - if (j > 2 * HZ) { - pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#lx ->cpu=%d\n", - rcu_state.name, j, - (long)rcu_seq_current(&rcu_state.gp_seq), - READ_ONCE(rcu_state.gp_flags), - gp_state_getname(rcu_state.gp_state), rcu_state.gp_state, - gpk ? gpk->state : ~0, gpk ? task_cpu(gpk) : -1); - if (gpk) { - pr_err("RCU grace-period kthread stack dump:\n"); - sched_show_task(gpk); - wake_up_process(gpk); - } - } -} - -/* - * Dump stacks of all tasks running on stalled CPUs. First try using - * NMIs, but fall back to manual remote stack tracing on architectures - * that don't support NMI-based stack dumps. The NMI-triggered stack - * traces are more accurate because they are printed by the target CPU. - */ -static void rcu_dump_cpu_stacks(void) -{ - int cpu; - unsigned long flags; - struct rcu_node *rnp; - - rcu_for_each_leaf_node(rnp) { - raw_spin_lock_irqsave_rcu_node(rnp, flags); - for_each_leaf_node_possible_cpu(rnp, cpu) - if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) - if (!trigger_single_cpu_backtrace(cpu)) - dump_cpu_task(cpu); - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - } -} - -/* - * If too much time has passed in the current grace period, and if - * so configured, go kick the relevant kthreads. - */ -static void rcu_stall_kick_kthreads(void) -{ - unsigned long j; - - if (!rcu_kick_kthreads) - return; - j = READ_ONCE(rcu_state.jiffies_kick_kthreads); - if (time_after(jiffies, j) && rcu_state.gp_kthread && - (rcu_gp_in_progress() || READ_ONCE(rcu_state.gp_flags))) { - WARN_ONCE(1, "Kicking %s grace-period kthread\n", - rcu_state.name); - rcu_ftrace_dump(DUMP_ALL); - wake_up_process(rcu_state.gp_kthread); - WRITE_ONCE(rcu_state.jiffies_kick_kthreads, j + HZ); - } -} - -static void panic_on_rcu_stall(void) -{ - if (sysctl_panic_on_rcu_stall) - panic("RCU Stall\n"); -} - -static void print_other_cpu_stall(unsigned long gp_seq) -{ - int cpu; - unsigned long flags; - unsigned long gpa; - unsigned long j; - int ndetected = 0; - struct rcu_node *rnp = rcu_get_root(); - long totqlen = 0; - - /* Kick and suppress, if so configured. */ - rcu_stall_kick_kthreads(); - if (rcu_cpu_stall_suppress) - return; - - /* - * OK, time to rat on our buddy... - * See Documentation/RCU/stallwarn.txt for info on how to debug - * RCU CPU stall warnings. - */ - pr_err("INFO: %s detected stalls on CPUs/tasks:", rcu_state.name); - print_cpu_stall_info_begin(); - rcu_for_each_leaf_node(rnp) { - raw_spin_lock_irqsave_rcu_node(rnp, flags); - ndetected += rcu_print_task_stall(rnp); - if (rnp->qsmask != 0) { - for_each_leaf_node_possible_cpu(rnp, cpu) - if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) { - print_cpu_stall_info(cpu); - ndetected++; - } - } - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - } - - print_cpu_stall_info_end(); - for_each_possible_cpu(cpu) - totqlen += rcu_get_n_cbs_cpu(cpu); - pr_cont("(detected by %d, t=%ld jiffies, g=%ld, q=%lu)\n", - smp_processor_id(), (long)(jiffies - rcu_state.gp_start), - (long)rcu_seq_current(&rcu_state.gp_seq), totqlen); - if (ndetected) { - rcu_dump_cpu_stacks(); - - /* Complain about tasks blocking the grace period. */ - rcu_print_detail_task_stall(); - } else { - if (rcu_seq_current(&rcu_state.gp_seq) != gp_seq) { - pr_err("INFO: Stall ended before state dump start\n"); - } else { - j = jiffies; - gpa = READ_ONCE(rcu_state.gp_activity); - pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n", - rcu_state.name, j - gpa, j, gpa, - READ_ONCE(jiffies_till_next_fqs), - rcu_get_root()->qsmask); - /* In this case, the current CPU might be at fault. */ - sched_show_task(current); - } - } - /* Rewrite if needed in case of slow consoles. */ - if (ULONG_CMP_GE(jiffies, READ_ONCE(rcu_state.jiffies_stall))) - WRITE_ONCE(rcu_state.jiffies_stall, - jiffies + 3 * rcu_jiffies_till_stall_check() + 3); - - rcu_check_gp_kthread_starvation(); - - panic_on_rcu_stall(); - - rcu_force_quiescent_state(); /* Kick them all. */ -} - -static void print_cpu_stall(void) -{ - int cpu; - unsigned long flags; - struct rcu_data *rdp = this_cpu_ptr(&rcu_data); - struct rcu_node *rnp = rcu_get_root(); - long totqlen = 0; - - /* Kick and suppress, if so configured. */ - rcu_stall_kick_kthreads(); - if (rcu_cpu_stall_suppress) - return; - - /* - * OK, time to rat on ourselves... - * See Documentation/RCU/stallwarn.txt for info on how to debug - * RCU CPU stall warnings. - */ - pr_err("INFO: %s self-detected stall on CPU", rcu_state.name); - print_cpu_stall_info_begin(); - raw_spin_lock_irqsave_rcu_node(rdp->mynode, flags); - print_cpu_stall_info(smp_processor_id()); - raw_spin_unlock_irqrestore_rcu_node(rdp->mynode, flags); - print_cpu_stall_info_end(); - for_each_possible_cpu(cpu) - totqlen += rcu_get_n_cbs_cpu(cpu); - pr_cont(" (t=%lu jiffies g=%ld q=%lu)\n", - jiffies - rcu_state.gp_start, - (long)rcu_seq_current(&rcu_state.gp_seq), totqlen); - - rcu_check_gp_kthread_starvation(); - - rcu_dump_cpu_stacks(); - - raw_spin_lock_irqsave_rcu_node(rnp, flags); - /* Rewrite if needed in case of slow consoles. */ - if (ULONG_CMP_GE(jiffies, READ_ONCE(rcu_state.jiffies_stall))) - WRITE_ONCE(rcu_state.jiffies_stall, - jiffies + 3 * rcu_jiffies_till_stall_check() + 3); - raw_spin_unlock_irqrestore_rcu_node(rnp, flags); - - panic_on_rcu_stall(); - - /* - * Attempt to revive the RCU machinery by forcing a context switch. - * - * A context switch would normally allow the RCU state machine to make - * progress and it could be we're stuck in kernel space without context - * switches for an entirely unreasonable amount of time. - */ - set_tsk_need_resched(current); - set_preempt_need_resched(); -} - -static void check_cpu_stall(struct rcu_data *rdp) -{ - unsigned long gs1; - unsigned long gs2; - unsigned long gps; - unsigned long j; - unsigned long jn; - unsigned long js; - struct rcu_node *rnp; - - if ((rcu_cpu_stall_suppress && !rcu_kick_kthreads) || - !rcu_gp_in_progress()) - return; - rcu_stall_kick_kthreads(); - j = jiffies; - - /* - * Lots of memory barriers to reject false positives. - * - * The idea is to pick up rcu_state.gp_seq, then - * rcu_state.jiffies_stall, then rcu_state.gp_start, and finally - * another copy of rcu_state.gp_seq. These values are updated in - * the opposite order with memory barriers (or equivalent) during - * grace-period initialization and cleanup. Now, a false positive - * can occur if we get an new value of rcu_state.gp_start and a old - * value of rcu_state.jiffies_stall. But given the memory barriers, - * the only way that this can happen is if one grace period ends - * and another starts between these two fetches. This is detected - * by comparing the second fetch of rcu_state.gp_seq with the - * previous fetch from rcu_state.gp_seq. - * - * Given this check, comparisons of jiffies, rcu_state.jiffies_stall, - * and rcu_state.gp_start suffice to forestall false positives. - */ - gs1 = READ_ONCE(rcu_state.gp_seq); - smp_rmb(); /* Pick up ->gp_seq first... */ - js = READ_ONCE(rcu_state.jiffies_stall); - smp_rmb(); /* ...then ->jiffies_stall before the rest... */ - gps = READ_ONCE(rcu_state.gp_start); - smp_rmb(); /* ...and finally ->gp_start before ->gp_seq again. */ - gs2 = READ_ONCE(rcu_state.gp_seq); - if (gs1 != gs2 || - ULONG_CMP_LT(j, js) || - ULONG_CMP_GE(gps, js)) - return; /* No stall or GP completed since entering function. */ - rnp = rdp->mynode; - jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; - if (rcu_gp_in_progress() && - (READ_ONCE(rnp->qsmask) & rdp->grpmask) && - cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) { - - /* We haven't checked in, so go dump stack. */ - print_cpu_stall(); - - } else if (rcu_gp_in_progress() && - ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) && - cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) { - - /* They had a few time units to dump stack, so complain. */ - print_other_cpu_stall(gs2); - } -} - -/** - * rcu_cpu_stall_reset - prevent further stall warnings in current grace period - * - * Set the stall-warning timeout way off into the future, thus preventing - * any RCU CPU stall-warning messages from appearing in the current set of - * RCU grace periods. - * - * The caller must disable hard irqs. - */ -void rcu_cpu_stall_reset(void) -{ - WRITE_ONCE(rcu_state.jiffies_stall, jiffies + ULONG_MAX / 2); -} - /* Trace-event wrapper function for trace_rcu_future_grace_period. */ static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, unsigned long gp_seq_req, const char *s) |