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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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85f1abe001
Even with the wait-loop fixed, there is a further issue with kthread_parkme(). Upon hotplug, when we do takedown_cpu(), smpboot_park_threads() can return before all those threads are in fact blocked, due to the placement of the complete() in __kthread_parkme(). When that happens, sched_cpu_dying() -> migrate_tasks() can end up migrating such a still runnable task onto another CPU. Normally the task will have hit schedule() and gone to sleep by the time we do kthread_unpark(), which will then do __kthread_bind() to re-bind the task to the correct CPU. However, when we loose the initial TASK_PARKED store to the concurrent wakeup issue described previously, do the complete(), get migrated, it is possible to either: - observe kthread_unpark()'s clearing of SHOULD_PARK and terminate the park and set TASK_RUNNING, or - __kthread_bind()'s wait_task_inactive() to observe the competing TASK_RUNNING store. Either way the WARN() in __kthread_bind() will trigger and fail to correctly set the CPU affinity. Fix this by only issuing the complete() when the kthread has scheduled out. This does away with all the icky 'still running' nonsense. The alternative is to promote TASK_PARKED to a special state, this guarantees wait_task_inactive() cannot observe a 'stale' TASK_RUNNING and we'll end up doing the right thing, but this preserves the whole icky business of potentially migating the still runnable thing. Reported-by: Gaurav Kohli <gkohli@codeaurora.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
213 lines
6.6 KiB
C
213 lines
6.6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#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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#include <linux/cgroup.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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/**
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* kthread_create - create a kthread on the current node
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* @threadfn: the function to run in the thread
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* @data: data pointer for @threadfn()
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* @namefmt: printf-style format string for the thread name
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* @arg...: arguments for @namefmt.
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*
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* This macro will create a kthread on the current node, leaving it in
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* the stopped state. This is just a helper for kthread_create_on_node();
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* see the documentation there for more details.
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*/
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#define kthread_create(threadfn, data, namefmt, arg...) \
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kthread_create_on_node(threadfn, data, NUMA_NO_NODE, 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 free_kthread_struct(struct task_struct *k);
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void kthread_bind(struct task_struct *k, unsigned int cpu);
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void kthread_bind_mask(struct task_struct *k, const struct cpumask *mask);
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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 *kthread_probe_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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void kthread_park_complete(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/kthread_flush_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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void kthread_delayed_work_timer_fn(struct timer_list *t);
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enum {
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KTW_FREEZABLE = 1 << 0, /* freeze during suspend */
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};
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struct kthread_worker {
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unsigned int flags;
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spinlock_t lock;
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struct list_head work_list;
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struct list_head delayed_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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struct kthread_worker *worker;
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/* Number of canceling calls that are running at the moment. */
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int canceling;
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};
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struct kthread_delayed_work {
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struct kthread_work work;
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struct timer_list timer;
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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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.delayed_work_list = LIST_HEAD_INIT((worker).delayed_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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}
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#define KTHREAD_DELAYED_WORK_INIT(dwork, fn) { \
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.work = KTHREAD_WORK_INIT((dwork).work, (fn)), \
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.timer = __TIMER_INITIALIZER(kthread_delayed_work_timer_fn,\
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TIMER_IRQSAFE), \
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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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#define DEFINE_KTHREAD_DELAYED_WORK(dwork, fn) \
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struct kthread_delayed_work dwork = \
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KTHREAD_DELAYED_WORK_INIT(dwork, fn)
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/*
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* kthread_worker.lock needs its own lockdep class key when defined on
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* stack with lockdep enabled. Use the following macros in such cases.
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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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({ kthread_init_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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#else
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# define DEFINE_KTHREAD_WORKER_ONSTACK(worker) DEFINE_KTHREAD_WORKER(worker)
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#endif
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extern void __kthread_init_worker(struct kthread_worker *worker,
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const char *name, struct lock_class_key *key);
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#define kthread_init_worker(worker) \
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do { \
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static struct lock_class_key __key; \
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__kthread_init_worker((worker), "("#worker")->lock", &__key); \
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} while (0)
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#define kthread_init_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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} while (0)
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#define kthread_init_delayed_work(dwork, fn) \
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do { \
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kthread_init_work(&(dwork)->work, (fn)); \
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__init_timer(&(dwork)->timer, \
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kthread_delayed_work_timer_fn, \
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TIMER_IRQSAFE); \
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} while (0)
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int kthread_worker_fn(void *worker_ptr);
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__printf(2, 3)
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struct kthread_worker *
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kthread_create_worker(unsigned int flags, const char namefmt[], ...);
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__printf(3, 4) struct kthread_worker *
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kthread_create_worker_on_cpu(int cpu, unsigned int flags,
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const char namefmt[], ...);
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bool kthread_queue_work(struct kthread_worker *worker,
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struct kthread_work *work);
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bool kthread_queue_delayed_work(struct kthread_worker *worker,
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struct kthread_delayed_work *dwork,
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unsigned long delay);
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bool kthread_mod_delayed_work(struct kthread_worker *worker,
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struct kthread_delayed_work *dwork,
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unsigned long delay);
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void kthread_flush_work(struct kthread_work *work);
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void kthread_flush_worker(struct kthread_worker *worker);
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bool kthread_cancel_work_sync(struct kthread_work *work);
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bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *work);
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void kthread_destroy_worker(struct kthread_worker *worker);
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#ifdef CONFIG_BLK_CGROUP
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void kthread_associate_blkcg(struct cgroup_subsys_state *css);
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struct cgroup_subsys_state *kthread_blkcg(void);
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#else
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static inline void kthread_associate_blkcg(struct cgroup_subsys_state *css) { }
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static inline struct cgroup_subsys_state *kthread_blkcg(void)
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{
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return NULL;
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}
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#endif
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#endif /* _LINUX_KTHREAD_H */
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