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![Tejun Heo](/assets/img/avatar_default.png)
One of the problems that arise when converting dedicated custom threadpool to workqueue is that the shared worker pool used by workqueue anonimizes each worker making it more difficult to identify what the worker was doing on which target from the output of sysrq-t or debug dump from oops, BUG() and friends. For example, after writeback is converted to use workqueue instead of priviate thread pool, there's no easy to tell which backing device a writeback work item was working on at the time of task dump, which, according to our writeback brethren, is important in tracking down issues with a lot of mounted file systems on a lot of different devices. This patchset implements a way for a work function to mark its execution instance so that task dump of the worker task includes information to indicate what the work item was doing. An example WARN dump would look like the following. WARNING: at fs/fs-writeback.c:1015 bdi_writeback_workfn+0x2b4/0x3c0() Modules linked in: CPU: 0 Pid: 28 Comm: kworker/u18:0 Not tainted 3.9.0-rc1-work+ #24 Hardware name: empty empty/S3992, BIOS 080011 10/26/2007 Workqueue: writeback bdi_writeback_workfn (flush-8:16) ffffffff820a3a98 ffff88015b927cb8 ffffffff81c61855 ffff88015b927cf8 ffffffff8108f500 0000000000000000 ffff88007a171948 ffff88007a1716b0 ffff88015b49df00 ffff88015b8d3940 0000000000000000 ffff88015b927d08 Call Trace: [<ffffffff81c61855>] dump_stack+0x19/0x1b [<ffffffff8108f500>] warn_slowpath_common+0x70/0xa0 ... This patch: Implement probe_kthread_data() which returns kthread_data if accessible. The function is equivalent to kthread_data() except that the specified @task may not be a kthread or its vfork_done is already cleared rendering struct kthread inaccessible. In the former case, probe_kthread_data() may return any value. In the latter, NULL. This will be used to safely print debug information without affecting synchronization in the normal paths. Workqueue debug info printing on dump_stack() and friends will make use of it. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Acked-by: Jan Kara <jack@suse.cz> Cc: Dave Chinner <david@fromorbit.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
140 lines
4.4 KiB
C
140 lines
4.4 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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struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
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void *data,
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unsigned int cpu,
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const char *namefmt);
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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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bool kthread_should_stop(void);
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bool kthread_should_park(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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void *probe_kthread_data(struct task_struct *k);
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int kthread_park(struct task_struct *k);
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void kthread_unpark(struct task_struct *k);
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void kthread_parkme(void);
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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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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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struct kthread_work *current_work;
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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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struct kthread_worker *worker;
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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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}
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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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