diff options
-rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 5 | ||||
-rw-r--r-- | kernel/rcu/rcu.h | 1 | ||||
-rw-r--r-- | kernel/rcu/tree_exp.h | 41 | ||||
-rw-r--r-- | kernel/rcu/update.c | 2 |
4 files changed, 49 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 6cfa6e3996cf..aa453f9202d8 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5113,6 +5113,11 @@ rcupdate.rcu_cpu_stall_timeout to be used (after conversion from seconds to milliseconds). + rcupdate.rcu_exp_stall_task_details= [KNL] + Print stack dumps of any tasks blocking the + current expedited RCU grace period during an + expedited RCU CPU stall warning. + rcupdate.rcu_expedited= [KNL] Use expedited grace-period primitives, for example, synchronize_rcu_expedited() instead diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index c5aa934de59b..fa640c45172e 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -224,6 +224,7 @@ extern int rcu_cpu_stall_ftrace_dump; extern int rcu_cpu_stall_suppress; extern int rcu_cpu_stall_timeout; extern int rcu_exp_cpu_stall_timeout; +extern bool rcu_exp_stall_task_details __read_mostly; int rcu_jiffies_till_stall_check(void); int rcu_exp_jiffies_till_stall_check(void); diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 927abaf6c822..249c2967d9e6 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -11,6 +11,7 @@ static void rcu_exp_handler(void *unused); static int rcu_print_task_exp_stall(struct rcu_node *rnp); +static void rcu_exp_print_detail_task_stall_rnp(struct rcu_node *rnp); /* * Record the start of an expedited grace period. @@ -671,6 +672,7 @@ static void synchronize_rcu_expedited_wait(void) dump_cpu_task(cpu); preempt_enable(); } + rcu_exp_print_detail_task_stall_rnp(rnp); } jiffies_stall = 3 * rcu_exp_jiffies_till_stall_check() + 3; panic_on_rcu_stall(); @@ -813,6 +815,36 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp) return ndetected; } +/* + * Scan the current list of tasks blocked within RCU read-side critical + * sections, dumping the stack of each that is blocking the current + * expedited grace period. + */ +static void rcu_exp_print_detail_task_stall_rnp(struct rcu_node *rnp) +{ + unsigned long flags; + struct task_struct *t; + + if (!rcu_exp_stall_task_details) + return; + raw_spin_lock_irqsave_rcu_node(rnp, flags); + if (!READ_ONCE(rnp->exp_tasks)) { + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); + return; + } + t = list_entry(rnp->exp_tasks->prev, + struct task_struct, rcu_node_entry); + list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) { + /* + * We could be printing a lot while holding a spinlock. + * Avoid triggering hard lockup. + */ + touch_nmi_watchdog(); + sched_show_task(t); + } + raw_spin_unlock_irqrestore_rcu_node(rnp, flags); +} + #else /* #ifdef CONFIG_PREEMPT_RCU */ /* Request an expedited quiescent state. */ @@ -885,6 +917,15 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp) return 0; } +/* + * Because preemptible RCU does not exist, we never have to print out + * tasks blocked within RCU read-side critical sections that are blocking + * the current expedited grace period. + */ +static void rcu_exp_print_detail_task_stall_rnp(struct rcu_node *rnp) +{ +} + #endif /* #else #ifdef CONFIG_PREEMPT_RCU */ /** diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 587b97c40191..6ed5020aee6d 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -509,6 +509,8 @@ int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT; module_param(rcu_cpu_stall_timeout, int, 0644); int rcu_exp_cpu_stall_timeout __read_mostly = CONFIG_RCU_EXP_CPU_STALL_TIMEOUT; module_param(rcu_exp_cpu_stall_timeout, int, 0644); +bool rcu_exp_stall_task_details __read_mostly; +module_param(rcu_exp_stall_task_details, bool, 0644); #endif /* #ifdef CONFIG_RCU_STALL_COMMON */ // Suppress boot-time RCU CPU stall warnings and rcutorture writer stall |