diff options
Diffstat (limited to 'kernel/hung_task.c')
| -rw-r--r-- | kernel/hung_task.c | 208 |
1 files changed, 172 insertions, 36 deletions
diff --git a/kernel/hung_task.c b/kernel/hung_task.c index 9a24574988d2..d2254c91450b 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -22,6 +22,9 @@ #include <linux/sched/signal.h> #include <linux/sched/debug.h> #include <linux/sched/sysctl.h> +#include <linux/hung_task.h> +#include <linux/rwsem.h> +#include <linux/sys_info.h> #include <trace/events/sched.h> @@ -31,6 +34,11 @@ static int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT; /* + * Total number of tasks detected as hung since boot: + */ +static unsigned long __read_mostly sysctl_hung_task_detect_count; + +/* * Limit number of tasks checked in a batch. * * This value controls the preemptibility of khungtaskd since preemption @@ -52,12 +60,17 @@ static unsigned long __read_mostly sysctl_hung_task_check_interval_secs; static int __read_mostly sysctl_hung_task_warnings = 10; static int __read_mostly did_panic; -static bool hung_task_show_lock; static bool hung_task_call_panic; -static bool hung_task_show_all_bt; static struct task_struct *watchdog_task; +/* + * A bitmask to control what kinds of system info to be printed when + * a hung task is detected, it could be task, memory, lock etc. Refer + * include/linux/sys_info.h for detailed bit definition. + */ +static unsigned long hung_task_si_mask; + #ifdef CONFIG_SMP /* * Should we dump all CPUs backtraces in a hung task event? @@ -73,7 +86,7 @@ static unsigned int __read_mostly sysctl_hung_task_all_cpu_backtrace; * hung task is detected: */ static unsigned int __read_mostly sysctl_hung_task_panic = - IS_ENABLED(CONFIG_BOOTPARAM_HUNG_TASK_PANIC); + CONFIG_BOOTPARAM_HUNG_TASK_PANIC; static int hung_task_panic(struct notifier_block *this, unsigned long event, void *ptr) @@ -87,16 +100,19 @@ static struct notifier_block panic_block = { .notifier_call = hung_task_panic, }; -static void check_hung_task(struct task_struct *t, unsigned long timeout) +static bool task_is_hung(struct task_struct *t, unsigned long timeout) { unsigned long switch_count = t->nvcsw + t->nivcsw; + unsigned int state = READ_ONCE(t->__state); /* - * Ensure the task is not frozen. - * Also, skip vfork and any other user process that freezer should skip. + * skip the TASK_KILLABLE tasks -- these can be killed + * skip the TASK_IDLE tasks -- those are genuinely idle + * skip the TASK_FROZEN task -- it reasonably stops scheduling by freezer */ - if (unlikely(READ_ONCE(t->__state) & TASK_FROZEN)) - return; + if (!(state & TASK_UNINTERRUPTIBLE) || + (state & (TASK_WAKEKILL | TASK_NOLOAD | TASK_FROZEN))) + return false; /* * When a freshly created task is scheduled once, changes its state to @@ -104,21 +120,128 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) * musn't be checked. */ if (unlikely(!switch_count)) - return; + return false; if (switch_count != t->last_switch_count) { t->last_switch_count = switch_count; t->last_switch_time = jiffies; - return; + return false; } if (time_is_after_jiffies(t->last_switch_time + timeout * HZ)) + return false; + + return true; +} + +#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER +static void debug_show_blocker(struct task_struct *task, unsigned long timeout) +{ + struct task_struct *g, *t; + unsigned long owner, blocker, blocker_type; + const char *rwsem_blocked_by, *rwsem_blocked_as; + + RCU_LOCKDEP_WARN(!rcu_read_lock_held(), "No rcu lock held"); + + blocker = READ_ONCE(task->blocker); + if (!blocker) + return; + + blocker_type = hung_task_get_blocker_type(blocker); + + switch (blocker_type) { + case BLOCKER_TYPE_MUTEX: + owner = mutex_get_owner(hung_task_blocker_to_lock(blocker)); + break; + case BLOCKER_TYPE_SEM: + owner = sem_last_holder(hung_task_blocker_to_lock(blocker)); + break; + case BLOCKER_TYPE_RWSEM_READER: + case BLOCKER_TYPE_RWSEM_WRITER: + owner = (unsigned long)rwsem_owner( + hung_task_blocker_to_lock(blocker)); + rwsem_blocked_as = (blocker_type == BLOCKER_TYPE_RWSEM_READER) ? + "reader" : "writer"; + rwsem_blocked_by = is_rwsem_reader_owned( + hung_task_blocker_to_lock(blocker)) ? + "reader" : "writer"; + break; + default: + WARN_ON_ONCE(1); + return; + } + + + if (unlikely(!owner)) { + switch (blocker_type) { + case BLOCKER_TYPE_MUTEX: + pr_err("INFO: task %s:%d is blocked on a mutex, but the owner is not found.\n", + task->comm, task->pid); + break; + case BLOCKER_TYPE_SEM: + pr_err("INFO: task %s:%d is blocked on a semaphore, but the last holder is not found.\n", + task->comm, task->pid); + break; + case BLOCKER_TYPE_RWSEM_READER: + case BLOCKER_TYPE_RWSEM_WRITER: + pr_err("INFO: task %s:%d is blocked on an rw-semaphore, but the owner is not found.\n", + task->comm, task->pid); + break; + } + return; + } + + /* Ensure the owner information is correct. */ + for_each_process_thread(g, t) { + if ((unsigned long)t != owner) + continue; + + switch (blocker_type) { + case BLOCKER_TYPE_MUTEX: + pr_err("INFO: task %s:%d is blocked on a mutex likely owned by task %s:%d.\n", + task->comm, task->pid, t->comm, t->pid); + break; + case BLOCKER_TYPE_SEM: + pr_err("INFO: task %s:%d blocked on a semaphore likely last held by task %s:%d\n", + task->comm, task->pid, t->comm, t->pid); + break; + case BLOCKER_TYPE_RWSEM_READER: + case BLOCKER_TYPE_RWSEM_WRITER: + pr_err("INFO: task %s:%d <%s> blocked on an rw-semaphore likely owned by task %s:%d <%s>\n", + task->comm, task->pid, rwsem_blocked_as, t->comm, + t->pid, rwsem_blocked_by); + break; + } + /* Avoid duplicated task dump, skip if the task is also hung. */ + if (!task_is_hung(t, timeout)) + sched_show_task(t); + return; + } +} +#else +static inline void debug_show_blocker(struct task_struct *task, unsigned long timeout) +{ +} +#endif + +static void check_hung_task(struct task_struct *t, unsigned long timeout, + unsigned long prev_detect_count) +{ + unsigned long total_hung_task; + + if (!task_is_hung(t, timeout)) return; + /* + * This counter tracks the total number of tasks detected as hung + * since boot. + */ + sysctl_hung_task_detect_count++; + + total_hung_task = sysctl_hung_task_detect_count - prev_detect_count; trace_sched_process_hang(t); - if (sysctl_hung_task_panic) { + if (sysctl_hung_task_panic && total_hung_task >= sysctl_hung_task_panic) { console_verbose(); - hung_task_show_lock = true; hung_task_call_panic = true; } @@ -126,7 +249,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) * Ok, the task did not get scheduled for more than 2 minutes, * complain: */ - if (sysctl_hung_task_warnings) { + if (sysctl_hung_task_warnings || hung_task_call_panic) { if (sysctl_hung_task_warnings > 0) sysctl_hung_task_warnings--; pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n", @@ -135,13 +258,13 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) print_tainted(), init_utsname()->release, (int)strcspn(init_utsname()->version, " "), init_utsname()->version); + if (t->flags & PF_POSTCOREDUMP) + pr_err(" Blocked by coredump.\n"); pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" " disables this message.\n"); sched_show_task(t); - hung_task_show_lock = true; + debug_show_blocker(t, timeout); - if (sysctl_hung_task_all_cpu_backtrace) - hung_task_show_all_bt = true; if (!sysctl_hung_task_warnings) pr_info("Future hung task reports are suppressed, see sysctl kernel.hung_task_warnings\n"); } @@ -182,6 +305,9 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) int max_count = sysctl_hung_task_check_count; unsigned long last_break = jiffies; struct task_struct *g, *t; + unsigned long prev_detect_count = sysctl_hung_task_detect_count; + int need_warning = sysctl_hung_task_warnings; + unsigned long si_mask = hung_task_si_mask; /* * If the system crashed already then all bets are off, @@ -190,10 +316,9 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) if (test_taint(TAINT_DIE) || did_panic) return; - hung_task_show_lock = false; + rcu_read_lock(); for_each_process_thread(g, t) { - unsigned int state; if (!max_count--) goto unlock; @@ -202,26 +327,24 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout) goto unlock; last_break = jiffies; } - /* - * skip the TASK_KILLABLE tasks -- these can be killed - * skip the TASK_IDLE tasks -- those are genuinely idle - */ - state = READ_ONCE(t->__state); - if ((state & TASK_UNINTERRUPTIBLE) && - !(state & TASK_WAKEKILL) && - !(state & TASK_NOLOAD)) - check_hung_task(t, timeout); + + check_hung_task(t, timeout, prev_detect_count); } unlock: rcu_read_unlock(); - if (hung_task_show_lock) - debug_show_all_locks(); - if (hung_task_show_all_bt) { - hung_task_show_all_bt = false; - trigger_all_cpu_backtrace(); + if (!(sysctl_hung_task_detect_count - prev_detect_count)) + return; + + if (need_warning || hung_task_call_panic) { + si_mask |= SYS_INFO_LOCKS; + + if (sysctl_hung_task_all_cpu_backtrace) + si_mask |= SYS_INFO_ALL_BT; } + sys_info(si_mask); + if (hung_task_call_panic) panic("hung_task: blocked tasks"); } @@ -238,7 +361,7 @@ static long hung_timeout_jiffies(unsigned long last_checked, /* * Process updating of timeout sysctl */ -static int proc_dohung_task_timeout_secs(struct ctl_table *table, int write, +static int proc_dohung_task_timeout_secs(const struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { @@ -260,7 +383,7 @@ static int proc_dohung_task_timeout_secs(struct ctl_table *table, int write, * and hung_task_check_interval_secs */ static const unsigned long hung_task_timeout_max = (LONG_MAX / HZ); -static struct ctl_table hung_task_sysctls[] = { +static const struct ctl_table hung_task_sysctls[] = { #ifdef CONFIG_SMP { .procname = "hung_task_all_cpu_backtrace", @@ -279,7 +402,7 @@ static struct ctl_table hung_task_sysctls[] = { .mode = 0644, .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_ZERO, - .extra2 = SYSCTL_ONE, + .extra2 = SYSCTL_INT_MAX, }, { .procname = "hung_task_check_count", @@ -313,7 +436,20 @@ static struct ctl_table hung_task_sysctls[] = { .proc_handler = proc_dointvec_minmax, .extra1 = SYSCTL_NEG_ONE, }, - {} + { + .procname = "hung_task_detect_count", + .data = &sysctl_hung_task_detect_count, + .maxlen = sizeof(unsigned long), + .mode = 0444, + .proc_handler = proc_doulongvec_minmax, + }, + { + .procname = "hung_task_sys_info", + .data = &hung_task_si_mask, + .maxlen = sizeof(hung_task_si_mask), + .mode = 0644, + .proc_handler = sysctl_sys_info_handler, + }, }; static void __init hung_task_sysctl_init(void) |