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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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85ba2d862e
This extends wait_task_inactive() with a new argument so it can be used in a "soft" mode where it will check for the task changing state unexpectedly and back off. There is no change to existing callers. This lays the groundwork to allow robust, noninvasive tracing that can try to sample a blocked thread but back off safely if it wakes up. Signed-off-by: Roland McGrath <roland@redhat.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Reviewed-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
264 lines
7.2 KiB
C
264 lines
7.2 KiB
C
/* Kernel thread helper functions.
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* Copyright (C) 2004 IBM Corporation, Rusty Russell.
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*
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* Creation is done via kthreadd, so that we get a clean environment
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* even if we're invoked from userspace (think modprobe, hotplug cpu,
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* etc.).
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*/
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#include <linux/sched.h>
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#include <linux/kthread.h>
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#include <linux/completion.h>
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#include <linux/err.h>
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#include <linux/unistd.h>
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#include <linux/file.h>
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#include <linux/module.h>
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#include <linux/mutex.h>
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#define KTHREAD_NICE_LEVEL (-5)
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static DEFINE_SPINLOCK(kthread_create_lock);
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static LIST_HEAD(kthread_create_list);
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struct task_struct *kthreadd_task;
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struct kthread_create_info
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{
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/* Information passed to kthread() from kthreadd. */
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int (*threadfn)(void *data);
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void *data;
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struct completion started;
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/* Result passed back to kthread_create() from kthreadd. */
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struct task_struct *result;
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struct completion done;
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struct list_head list;
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};
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struct kthread_stop_info
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{
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struct task_struct *k;
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int err;
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struct completion done;
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};
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/* Thread stopping is done by setthing this var: lock serializes
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* multiple kthread_stop calls. */
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static DEFINE_MUTEX(kthread_stop_lock);
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static struct kthread_stop_info kthread_stop_info;
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/**
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* kthread_should_stop - should this kthread return now?
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*
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* When someone calls kthread_stop() on your kthread, it will be woken
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* and this will return true. You should then return, and your return
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* value will be passed through to kthread_stop().
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*/
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int kthread_should_stop(void)
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{
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return (kthread_stop_info.k == current);
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}
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EXPORT_SYMBOL(kthread_should_stop);
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static int kthread(void *_create)
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{
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struct kthread_create_info *create = _create;
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int (*threadfn)(void *data);
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void *data;
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int ret = -EINTR;
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/* Copy data: it's on kthread's stack */
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threadfn = create->threadfn;
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data = create->data;
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/* OK, tell user we're spawned, wait for stop or wakeup */
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__set_current_state(TASK_UNINTERRUPTIBLE);
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complete(&create->started);
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schedule();
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if (!kthread_should_stop())
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ret = threadfn(data);
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/* It might have exited on its own, w/o kthread_stop. Check. */
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if (kthread_should_stop()) {
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kthread_stop_info.err = ret;
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complete(&kthread_stop_info.done);
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}
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return 0;
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}
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static void create_kthread(struct kthread_create_info *create)
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{
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int pid;
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/* We want our own signal handler (we take no signals by default). */
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pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
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if (pid < 0) {
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create->result = ERR_PTR(pid);
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} else {
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struct sched_param param = { .sched_priority = 0 };
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wait_for_completion(&create->started);
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read_lock(&tasklist_lock);
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create->result = find_task_by_pid_ns(pid, &init_pid_ns);
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read_unlock(&tasklist_lock);
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/*
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* root may have changed our (kthreadd's) priority or CPU mask.
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* The kernel thread should not inherit these properties.
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*/
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sched_setscheduler(create->result, SCHED_NORMAL, ¶m);
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set_user_nice(create->result, KTHREAD_NICE_LEVEL);
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set_cpus_allowed_ptr(create->result, CPU_MASK_ALL_PTR);
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}
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complete(&create->done);
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}
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/**
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* kthread_create - create a kthread.
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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: This helper function creates and names a kernel
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* thread. The thread will be stopped: use wake_up_process() to start
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* it. See also kthread_run(), kthread_create_on_cpu().
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*
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* When woken, the thread will run @threadfn() with @data as its
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* argument. @threadfn() can either call do_exit() directly if it is a
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* standalone thread for which noone will call kthread_stop(), or
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* return when 'kthread_should_stop()' is true (which means
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* kthread_stop() has been called). The return value should be zero
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* or a negative error number; it will be passed to kthread_stop().
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*
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* Returns a task_struct or ERR_PTR(-ENOMEM).
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*/
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struct task_struct *kthread_create(int (*threadfn)(void *data),
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void *data,
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const char namefmt[],
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...)
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{
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struct kthread_create_info create;
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create.threadfn = threadfn;
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create.data = data;
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init_completion(&create.started);
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init_completion(&create.done);
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spin_lock(&kthread_create_lock);
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list_add_tail(&create.list, &kthread_create_list);
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spin_unlock(&kthread_create_lock);
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wake_up_process(kthreadd_task);
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wait_for_completion(&create.done);
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if (!IS_ERR(create.result)) {
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va_list args;
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va_start(args, namefmt);
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vsnprintf(create.result->comm, sizeof(create.result->comm),
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namefmt, args);
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va_end(args);
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}
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return create.result;
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}
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EXPORT_SYMBOL(kthread_create);
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/**
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* kthread_bind - bind a just-created kthread to a cpu.
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* @k: thread created by kthread_create().
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* @cpu: cpu (might not be online, must be possible) for @k to run on.
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*
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* Description: This function is equivalent to set_cpus_allowed(),
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* except that @cpu doesn't need to be online, and the thread must be
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* stopped (i.e., just returned from kthread_create()).
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*/
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void kthread_bind(struct task_struct *k, unsigned int cpu)
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{
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if (k->state != TASK_UNINTERRUPTIBLE) {
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WARN_ON(1);
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return;
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}
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/* Must have done schedule() in kthread() before we set_task_cpu */
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wait_task_inactive(k, 0);
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set_task_cpu(k, cpu);
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k->cpus_allowed = cpumask_of_cpu(cpu);
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k->rt.nr_cpus_allowed = 1;
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k->flags |= PF_THREAD_BOUND;
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}
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EXPORT_SYMBOL(kthread_bind);
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/**
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* kthread_stop - stop a thread created by kthread_create().
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* @k: thread created by kthread_create().
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*
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* Sets kthread_should_stop() for @k to return true, wakes it, and
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* waits for it to exit. Your threadfn() must not call do_exit()
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* itself if you use this function! This can also be called after
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* kthread_create() instead of calling wake_up_process(): the thread
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* will exit without calling threadfn().
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*
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* Returns the result of threadfn(), or %-EINTR if wake_up_process()
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* was never called.
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*/
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int kthread_stop(struct task_struct *k)
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{
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int ret;
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mutex_lock(&kthread_stop_lock);
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/* It could exit after stop_info.k set, but before wake_up_process. */
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get_task_struct(k);
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/* Must init completion *before* thread sees kthread_stop_info.k */
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init_completion(&kthread_stop_info.done);
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smp_wmb();
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/* Now set kthread_should_stop() to true, and wake it up. */
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kthread_stop_info.k = k;
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wake_up_process(k);
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put_task_struct(k);
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/* Once it dies, reset stop ptr, gather result and we're done. */
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wait_for_completion(&kthread_stop_info.done);
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kthread_stop_info.k = NULL;
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ret = kthread_stop_info.err;
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mutex_unlock(&kthread_stop_lock);
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return ret;
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}
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EXPORT_SYMBOL(kthread_stop);
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int kthreadd(void *unused)
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{
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struct task_struct *tsk = current;
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/* Setup a clean context for our children to inherit. */
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set_task_comm(tsk, "kthreadd");
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ignore_signals(tsk);
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set_user_nice(tsk, KTHREAD_NICE_LEVEL);
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set_cpus_allowed_ptr(tsk, CPU_MASK_ALL_PTR);
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current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;
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for (;;) {
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set_current_state(TASK_INTERRUPTIBLE);
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if (list_empty(&kthread_create_list))
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schedule();
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__set_current_state(TASK_RUNNING);
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spin_lock(&kthread_create_lock);
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while (!list_empty(&kthread_create_list)) {
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struct kthread_create_info *create;
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create = list_entry(kthread_create_list.next,
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struct kthread_create_info, list);
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list_del_init(&create->list);
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spin_unlock(&kthread_create_lock);
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create_kthread(create);
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spin_lock(&kthread_create_lock);
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}
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spin_unlock(&kthread_create_lock);
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}
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return 0;
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}
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