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| author | Paul E. McKenney <paulmck@kernel.org> | 2022-12-20 05:02:20 +0300 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2023-01-04 04:47:44 +0300 |
| commit | 92987fe8bdd1cbec61919a394bb11316c5d860f4 (patch) | |
| tree | 2308b37ef7d2ebeb57c0a2391a51fccce00d53d1 /kernel/rcu | |
| parent | 748bf47a89d722c7e77f8700705e2189be14e99e (diff) | |
| download | linux-92987fe8bdd1cbec61919a394bb11316c5d860f4.tar.xz | |
rcu: Allow expedited RCU CPU stall warnings to dump task stacks
This commit introduces the rcupdate.rcu_exp_stall_task_details kernel
boot parameter, which cause expedited RCU CPU stall warnings to dump
the stacks of any tasks blocking the current expedited grace period.
Reported-by: David Howells <dhowells@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -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 |
3 files changed, 44 insertions, 0 deletions
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 |