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e297cd54 MC |
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 | ||
f9010dbd MC |
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 | ||
e297cd54 MC |
23 | static int vhost_task_fn(void *data) |
24 | { | |
25 | struct vhost_task *vtsk = data; | |
f9010dbd MC |
26 | bool dead = false; |
27 | ||
28 | for (;;) { | |
29 | bool did_work; | |
30 | ||
f9010dbd MC |
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); | |
43 | if (dead) | |
44 | clear_thread_flag(TIF_SIGPENDING); | |
45 | } | |
46 | ||
4b13cbef MC |
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 | ||
f9010dbd | 55 | did_work = vtsk->fn(vtsk->data); |
4b13cbef | 56 | if (!did_work) |
f9010dbd | 57 | schedule(); |
f9010dbd | 58 | } |
e297cd54 | 59 | |
e297cd54 | 60 | complete(&vtsk->exited); |
f9010dbd MC |
61 | do_exit(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(vtsk->task); | |
e297cd54 | 73 | } |
f9010dbd | 74 | EXPORT_SYMBOL_GPL(vhost_task_wake); |
e297cd54 MC |
75 | |
76 | /** | |
77 | * vhost_task_stop - stop a vhost_task | |
78 | * @vtsk: vhost_task to stop | |
79 | * | |
f9010dbd MC |
80 | * vhost_task_fn ensures the worker thread exits after |
81 | * VHOST_TASK_FLAGS_SOP becomes true. | |
e297cd54 MC |
82 | */ |
83 | void vhost_task_stop(struct vhost_task *vtsk) | |
84 | { | |
e297cd54 | 85 | set_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags); |
f9010dbd | 86 | vhost_task_wake(vtsk); |
e297cd54 MC |
87 | /* |
88 | * Make sure vhost_task_fn is no longer accessing the vhost_task before | |
f9010dbd | 89 | * freeing it below. |
e297cd54 MC |
90 | */ |
91 | wait_for_completion(&vtsk->exited); | |
e297cd54 MC |
92 | kfree(vtsk); |
93 | } | |
94 | EXPORT_SYMBOL_GPL(vhost_task_stop); | |
95 | ||
96 | /** | |
f9010dbd MC |
97 | * vhost_task_create - create a copy of a task to be used by the kernel |
98 | * @fn: vhost worker function | |
e297cd54 MC |
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 | */ | |
f9010dbd | 106 | struct vhost_task *vhost_task_create(bool (*fn)(void *), void *arg, |
e297cd54 MC |
107 | const char *name) |
108 | { | |
109 | struct kernel_clone_args args = { | |
f9010dbd MC |
110 | .flags = CLONE_FS | CLONE_UNTRACED | CLONE_VM | |
111 | CLONE_THREAD | CLONE_SIGHAND, | |
e297cd54 MC |
112 | .exit_signal = 0, |
113 | .fn = vhost_task_fn, | |
114 | .name = name, | |
115 | .user_worker = 1, | |
116 | .no_files = 1, | |
e297cd54 MC |
117 | }; |
118 | struct vhost_task *vtsk; | |
119 | struct task_struct *tsk; | |
120 | ||
121 | vtsk = kzalloc(sizeof(*vtsk), GFP_KERNEL); | |
122 | if (!vtsk) | |
123 | return NULL; | |
124 | init_completion(&vtsk->exited); | |
125 | vtsk->data = arg; | |
126 | vtsk->fn = fn; | |
127 | ||
128 | args.fn_arg = vtsk; | |
129 | ||
130 | tsk = copy_process(NULL, 0, NUMA_NO_NODE, &args); | |
131 | if (IS_ERR(tsk)) { | |
132 | kfree(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(vtsk->task); | |
148 | } | |
149 | EXPORT_SYMBOL_GPL(vhost_task_start); |