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![Tejun Heo](/assets/img/avatar_default.png)
Writeback and thinkpad_acpi have been using thaw_process() to prevent deadlock between the freezer and kthread_stop(); unfortunately, this is inherently racy - nothing prevents freezing from happening between thaw_process() and kthread_stop(). This patch implements kthread_freezable_should_stop() which enters refrigerator if necessary but is guaranteed to return if kthread_stop() is invoked. Both thaw_process() users are converted to use the new function. Note that this deadlock condition exists for many of freezable kthreads. They need to be converted to use the new should_stop or freezable workqueue. Tested with synthetic test case. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Henrique de Moraes Holschuh <ibm-acpi@hmh.eng.br> Cc: Jens Axboe <axboe@kernel.dk> Cc: Oleg Nesterov <oleg@redhat.com>
134 lines
4.2 KiB
C
134 lines
4.2 KiB
C
#ifndef _LINUX_KTHREAD_H
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#define _LINUX_KTHREAD_H
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/* Simple interface for creating and stopping kernel threads without mess. */
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#include <linux/err.h>
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#include <linux/sched.h>
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__printf(4, 5)
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struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
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void *data,
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int node,
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const char namefmt[], ...);
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#define kthread_create(threadfn, data, namefmt, arg...) \
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kthread_create_on_node(threadfn, data, -1, namefmt, ##arg)
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/**
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* kthread_run - create and wake a thread.
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* @threadfn: the function to run until signal_pending(current).
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* @data: data ptr for @threadfn.
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* @namefmt: printf-style name for the thread.
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*
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* Description: Convenient wrapper for kthread_create() followed by
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* wake_up_process(). Returns the kthread or ERR_PTR(-ENOMEM).
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*/
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#define kthread_run(threadfn, data, namefmt, ...) \
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({ \
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struct task_struct *__k \
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= kthread_create(threadfn, data, namefmt, ## __VA_ARGS__); \
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if (!IS_ERR(__k)) \
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wake_up_process(__k); \
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__k; \
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})
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void kthread_bind(struct task_struct *k, unsigned int cpu);
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int kthread_stop(struct task_struct *k);
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int kthread_should_stop(void);
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bool kthread_freezable_should_stop(bool *was_frozen);
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void *kthread_data(struct task_struct *k);
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int kthreadd(void *unused);
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extern struct task_struct *kthreadd_task;
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extern int tsk_fork_get_node(struct task_struct *tsk);
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/*
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* Simple work processor based on kthread.
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*
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* This provides easier way to make use of kthreads. A kthread_work
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* can be queued and flushed using queue/flush_kthread_work()
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* respectively. Queued kthread_works are processed by a kthread
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* running kthread_worker_fn().
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*
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* A kthread_work can't be freed while it is executing.
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*/
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struct kthread_work;
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typedef void (*kthread_work_func_t)(struct kthread_work *work);
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struct kthread_worker {
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spinlock_t lock;
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struct list_head work_list;
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struct task_struct *task;
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};
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struct kthread_work {
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struct list_head node;
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kthread_work_func_t func;
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wait_queue_head_t done;
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atomic_t flushing;
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int queue_seq;
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int done_seq;
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};
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#define KTHREAD_WORKER_INIT(worker) { \
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.lock = __SPIN_LOCK_UNLOCKED((worker).lock), \
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.work_list = LIST_HEAD_INIT((worker).work_list), \
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}
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#define KTHREAD_WORK_INIT(work, fn) { \
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.node = LIST_HEAD_INIT((work).node), \
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.func = (fn), \
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.done = __WAIT_QUEUE_HEAD_INITIALIZER((work).done), \
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.flushing = ATOMIC_INIT(0), \
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}
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#define DEFINE_KTHREAD_WORKER(worker) \
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struct kthread_worker worker = KTHREAD_WORKER_INIT(worker)
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#define DEFINE_KTHREAD_WORK(work, fn) \
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struct kthread_work work = KTHREAD_WORK_INIT(work, fn)
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/*
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* kthread_worker.lock and kthread_work.done need their own lockdep class
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* keys if they are defined on stack with lockdep enabled. Use the
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* following macros when defining them on stack.
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*/
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#ifdef CONFIG_LOCKDEP
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# define KTHREAD_WORKER_INIT_ONSTACK(worker) \
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({ init_kthread_worker(&worker); worker; })
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# define DEFINE_KTHREAD_WORKER_ONSTACK(worker) \
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struct kthread_worker worker = KTHREAD_WORKER_INIT_ONSTACK(worker)
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# define KTHREAD_WORK_INIT_ONSTACK(work, fn) \
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({ init_kthread_work((&work), fn); work; })
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# define DEFINE_KTHREAD_WORK_ONSTACK(work, fn) \
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struct kthread_work work = KTHREAD_WORK_INIT_ONSTACK(work, fn)
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#else
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# define DEFINE_KTHREAD_WORKER_ONSTACK(worker) DEFINE_KTHREAD_WORKER(worker)
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# define DEFINE_KTHREAD_WORK_ONSTACK(work, fn) DEFINE_KTHREAD_WORK(work, fn)
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#endif
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extern void __init_kthread_worker(struct kthread_worker *worker,
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const char *name, struct lock_class_key *key);
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#define init_kthread_worker(worker) \
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do { \
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static struct lock_class_key __key; \
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__init_kthread_worker((worker), "("#worker")->lock", &__key); \
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} while (0)
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#define init_kthread_work(work, fn) \
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do { \
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memset((work), 0, sizeof(struct kthread_work)); \
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INIT_LIST_HEAD(&(work)->node); \
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(work)->func = (fn); \
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init_waitqueue_head(&(work)->done); \
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} while (0)
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int kthread_worker_fn(void *worker_ptr);
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bool queue_kthread_work(struct kthread_worker *worker,
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struct kthread_work *work);
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void flush_kthread_work(struct kthread_work *work);
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void flush_kthread_worker(struct kthread_worker *worker);
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#endif /* _LINUX_KTHREAD_H */
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