diff options
| -rw-r--r-- | kernel/rcu/tree.h | 1 | ||||
| -rw-r--r-- | kernel/rcu/tree_stall.h | 180 |
2 files changed, 97 insertions, 84 deletions
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 49bf3b00bb50..099410dbcbe9 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -442,6 +442,5 @@ static void rcu_dynticks_task_enter(void); static void rcu_dynticks_task_exit(void); /* Forward declarations for tree_stall.h */ -static int rcu_print_task_stall(struct rcu_node *rnp); static void record_gp_stall_check_time(void); static void check_cpu_stall(struct rcu_data *rdp); diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 19b915380a6f..03ed47883d8a 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -7,6 +7,9 @@ * Author: Paul E. McKenney <paulmck@linux.ibm.com> */ +////////////////////////////////////////////////////////////////////////////// +// +// Controlling CPU stall warnings, including delay calculation. /* panic() on RCU Stall sysctl. */ int sysctl_panic_on_rcu_stall __read_mostly; @@ -17,6 +20,7 @@ int sysctl_panic_on_rcu_stall __read_mostly; #define RCU_STALL_DELAY_DELTA 0 #endif +/* Limit-check stall timeouts specified at boottime and runtime. */ int rcu_jiffies_till_stall_check(void) { int till_stall_check = READ_ONCE(rcu_cpu_stall_timeout); @@ -36,6 +40,7 @@ int rcu_jiffies_till_stall_check(void) } EXPORT_SYMBOL_GPL(rcu_jiffies_till_stall_check); +/* Don't do RCU CPU stall warnings during long sysrq printouts. */ void rcu_sysrq_start(void) { if (!rcu_cpu_stall_suppress) @@ -48,6 +53,7 @@ void rcu_sysrq_end(void) rcu_cpu_stall_suppress = 0; } +/* Don't print RCU CPU stall warnings during a kernel panic. */ static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr) { rcu_cpu_stall_suppress = 1; @@ -65,6 +71,78 @@ static int __init check_cpu_stall_init(void) } early_initcall(check_cpu_stall_init); +/* If so specified via sysctl, panic, yielding cleaner stall-warning output. */ +static void panic_on_rcu_stall(void) +{ + if (sysctl_panic_on_rcu_stall) + panic("RCU Stall\n"); +} + +/** + * 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); +} + +////////////////////////////////////////////////////////////////////////////// +// +// Interaction with RCU grace periods + +/* Start of new grace period, so record stall time (and forcing times). */ +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); +} + +/* Zero ->ticks_this_gp and snapshot the number of RCU softirq handlers. */ +static void zero_cpu_stall_ticks(struct rcu_data *rdp) +{ + rdp->ticks_this_gp = 0; + rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id()); + WRITE_ONCE(rdp->last_fqs_resched, jiffies); +} + +/* + * 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); + } +} + +////////////////////////////////////////////////////////////////////////////// +// +// Printing RCU CPU stall warnings + #ifdef CONFIG_PREEMPT /* @@ -137,43 +215,6 @@ static int rcu_print_task_stall(struct rcu_node *rnp) } #endif /* #else #ifdef CONFIG_PREEMPT */ -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 @@ -196,33 +237,6 @@ static void rcu_dump_cpu_stacks(void) } } -/* - * 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"); -} - #ifdef CONFIG_RCU_FAST_NO_HZ static void print_cpu_stall_fast_no_hz(char *cp, int cpu) @@ -295,12 +309,26 @@ static void print_cpu_stall_info(int cpu) fast_no_hz); } -/* Zero ->ticks_this_gp and snapshot the number of RCU softirq handlers. */ -static void zero_cpu_stall_ticks(struct rcu_data *rdp) +/* Complain about starvation of grace-period kthread. */ +static void rcu_check_gp_kthread_starvation(void) { - rdp->ticks_this_gp = 0; - rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id()); - WRITE_ONCE(rdp->last_fqs_resched, jiffies); + 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); + } + } } static void print_other_cpu_stall(unsigned long gp_seq) @@ -488,17 +516,3 @@ static void check_cpu_stall(struct rcu_data *rdp) 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); -} |