diff options
| -rw-r--r-- | include/linux/mutex.h | 2 | ||||
| -rw-r--r-- | include/linux/sched.h | 4 | ||||
| -rw-r--r-- | kernel/hung_task.c | 38 | ||||
| -rw-r--r-- | kernel/locking/mutex.c | 14 | ||||
| -rw-r--r-- | lib/Kconfig.debug | 11 |
5 files changed, 69 insertions, 0 deletions
diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 2bf91b57591b..2143d05116be 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -202,4 +202,6 @@ DEFINE_GUARD(mutex, struct mutex *, mutex_lock(_T), mutex_unlock(_T)) DEFINE_GUARD_COND(mutex, _try, mutex_trylock(_T)) DEFINE_GUARD_COND(mutex, _intr, mutex_lock_interruptible(_T) == 0) +extern unsigned long mutex_get_owner(struct mutex *lock); + #endif /* __LINUX_MUTEX_H */ diff --git a/include/linux/sched.h b/include/linux/sched.h index 9c15365a30c0..1419d94c8e87 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1217,6 +1217,10 @@ struct task_struct { struct mutex_waiter *blocked_on; #endif +#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER + struct mutex *blocker_mutex; +#endif + #ifdef CONFIG_DEBUG_ATOMIC_SLEEP int non_block_count; #endif diff --git a/kernel/hung_task.c b/kernel/hung_task.c index 04efa7a6e69b..dc898ec93463 100644 --- a/kernel/hung_task.c +++ b/kernel/hung_task.c @@ -93,6 +93,43 @@ static struct notifier_block panic_block = { .notifier_call = hung_task_panic, }; + +#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER +static void debug_show_blocker(struct task_struct *task) +{ + struct task_struct *g, *t; + unsigned long owner; + struct mutex *lock; + + RCU_LOCKDEP_WARN(!rcu_read_lock_held(), "No rcu lock held"); + + lock = READ_ONCE(task->blocker_mutex); + if (!lock) + return; + + owner = mutex_get_owner(lock); + if (unlikely(!owner)) { + pr_err("INFO: task %s:%d is blocked on a mutex, but the owner is not found.\n", + task->comm, task->pid); + return; + } + + /* Ensure the owner information is correct. */ + for_each_process_thread(g, t) { + if ((unsigned long)t == owner) { + 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); + sched_show_task(t); + return; + } + } +} +#else +static inline void debug_show_blocker(struct task_struct *task) +{ +} +#endif + static void check_hung_task(struct task_struct *t, unsigned long timeout) { unsigned long switch_count = t->nvcsw + t->nivcsw; @@ -152,6 +189,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" " disables this message.\n"); sched_show_task(t); + debug_show_blocker(t); hung_task_show_lock = true; if (sysctl_hung_task_all_cpu_backtrace) diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c index b36f23de48f1..6a543c204a14 100644 --- a/kernel/locking/mutex.c +++ b/kernel/locking/mutex.c @@ -72,6 +72,14 @@ static inline unsigned long __owner_flags(unsigned long owner) return owner & MUTEX_FLAGS; } +/* Do not use the return value as a pointer directly. */ +unsigned long mutex_get_owner(struct mutex *lock) +{ + unsigned long owner = atomic_long_read(&lock->owner); + + return (unsigned long)__owner_task(owner); +} + /* * Returns: __mutex_owner(lock) on failure or NULL on success. */ @@ -180,6 +188,9 @@ static void __mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter, struct list_head *list) { +#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER + WRITE_ONCE(current->blocker_mutex, lock); +#endif debug_mutex_add_waiter(lock, waiter, current); list_add_tail(&waiter->list, list); @@ -195,6 +206,9 @@ __mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter) __mutex_clear_flag(lock, MUTEX_FLAGS); debug_mutex_remove_waiter(lock, waiter, current); +#ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER + WRITE_ONCE(current->blocker_mutex, NULL); +#endif } /* diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 35796c290ca3..1f5943f6be75 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1260,6 +1260,17 @@ config BOOTPARAM_HUNG_TASK_PANIC Say N if unsure. +config DETECT_HUNG_TASK_BLOCKER + bool "Dump Hung Tasks Blocker" + depends on DETECT_HUNG_TASK + depends on !PREEMPT_RT + default y + help + Say Y here to show the blocker task's stacktrace who acquires + the mutex lock which "hung tasks" are waiting. + This will add overhead a bit but shows suspicious tasks and + call trace if it comes from waiting a mutex. + config WQ_WATCHDOG bool "Detect Workqueue Stalls" depends on DEBUG_KERNEL |