1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * Copyright (C) 2021 Oracle Corporation |
4 | */ |
5 | #include <linux/slab.h> |
6 | #include <linux/completion.h> |
7 | #include <linux/sched/task.h> |
8 | #include <linux/sched/vhost_task.h> |
9 | #include <linux/sched/signal.h> |
10 | |
11 | enum vhost_task_flags { |
12 | VHOST_TASK_FLAGS_STOP, |
13 | }; |
14 | |
15 | struct vhost_task { |
16 | bool (*fn)(void *data); |
17 | void *data; |
18 | struct completion exited; |
19 | unsigned long flags; |
20 | struct task_struct *task; |
21 | }; |
22 | |
23 | static int vhost_task_fn(void *data) |
24 | { |
25 | struct vhost_task *vtsk = data; |
26 | bool dead = false; |
27 | |
28 | for (;;) { |
29 | bool did_work; |
30 | |
31 | if (!dead && signal_pending(current)) { |
32 | struct ksignal ksig; |
33 | /* |
34 | * Calling get_signal will block in SIGSTOP, |
35 | * or clear fatal_signal_pending, but remember |
36 | * what was set. |
37 | * |
38 | * This thread won't actually exit until all |
39 | * of the file descriptors are closed, and |
40 | * the release function is called. |
41 | */ |
42 | dead = get_signal(ksig: &ksig); |
43 | if (dead) |
44 | clear_thread_flag(TIF_SIGPENDING); |
45 | } |
46 | |
47 | /* mb paired w/ vhost_task_stop */ |
48 | set_current_state(TASK_INTERRUPTIBLE); |
49 | |
50 | if (test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags)) { |
51 | __set_current_state(TASK_RUNNING); |
52 | break; |
53 | } |
54 | |
55 | did_work = vtsk->fn(vtsk->data); |
56 | if (!did_work) |
57 | schedule(); |
58 | } |
59 | |
60 | complete(&vtsk->exited); |
61 | do_exit(error_code: 0); |
62 | } |
63 | |
64 | /** |
65 | * vhost_task_wake - wakeup the vhost_task |
66 | * @vtsk: vhost_task to wake |
67 | * |
68 | * wake up the vhost_task worker thread |
69 | */ |
70 | void vhost_task_wake(struct vhost_task *vtsk) |
71 | { |
72 | wake_up_process(tsk: vtsk->task); |
73 | } |
74 | EXPORT_SYMBOL_GPL(vhost_task_wake); |
75 | |
76 | /** |
77 | * vhost_task_stop - stop a vhost_task |
78 | * @vtsk: vhost_task to stop |
79 | * |
80 | * vhost_task_fn ensures the worker thread exits after |
81 | * VHOST_TASK_FLAGS_SOP becomes true. |
82 | */ |
83 | void vhost_task_stop(struct vhost_task *vtsk) |
84 | { |
85 | set_bit(nr: VHOST_TASK_FLAGS_STOP, addr: &vtsk->flags); |
86 | vhost_task_wake(vtsk); |
87 | /* |
88 | * Make sure vhost_task_fn is no longer accessing the vhost_task before |
89 | * freeing it below. |
90 | */ |
91 | wait_for_completion(&vtsk->exited); |
92 | kfree(objp: vtsk); |
93 | } |
94 | EXPORT_SYMBOL_GPL(vhost_task_stop); |
95 | |
96 | /** |
97 | * vhost_task_create - create a copy of a task to be used by the kernel |
98 | * @fn: vhost worker function |
99 | * @arg: data to be passed to fn |
100 | * @name: the thread's name |
101 | * |
102 | * This returns a specialized task for use by the vhost layer or NULL on |
103 | * failure. The returned task is inactive, and the caller must fire it up |
104 | * through vhost_task_start(). |
105 | */ |
106 | struct vhost_task *vhost_task_create(bool (*fn)(void *), void *arg, |
107 | const char *name) |
108 | { |
109 | struct kernel_clone_args args = { |
110 | .flags = CLONE_FS | CLONE_UNTRACED | CLONE_VM | |
111 | CLONE_THREAD | CLONE_SIGHAND, |
112 | .exit_signal = 0, |
113 | .fn = vhost_task_fn, |
114 | .name = name, |
115 | .user_worker = 1, |
116 | .no_files = 1, |
117 | }; |
118 | struct vhost_task *vtsk; |
119 | struct task_struct *tsk; |
120 | |
121 | vtsk = kzalloc(size: sizeof(*vtsk), GFP_KERNEL); |
122 | if (!vtsk) |
123 | return NULL; |
124 | init_completion(x: &vtsk->exited); |
125 | vtsk->data = arg; |
126 | vtsk->fn = fn; |
127 | |
128 | args.fn_arg = vtsk; |
129 | |
130 | tsk = copy_process(NULL, trace: 0, NUMA_NO_NODE, args: &args); |
131 | if (IS_ERR(ptr: tsk)) { |
132 | kfree(objp: vtsk); |
133 | return NULL; |
134 | } |
135 | |
136 | vtsk->task = tsk; |
137 | return vtsk; |
138 | } |
139 | EXPORT_SYMBOL_GPL(vhost_task_create); |
140 | |
141 | /** |
142 | * vhost_task_start - start a vhost_task created with vhost_task_create |
143 | * @vtsk: vhost_task to wake up |
144 | */ |
145 | void vhost_task_start(struct vhost_task *vtsk) |
146 | { |
147 | wake_up_new_task(tsk: vtsk->task); |
148 | } |
149 | EXPORT_SYMBOL_GPL(vhost_task_start); |
150 | |