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| 2 | |
| 3 | * Copyright (C) 2021 Oracle Corporation
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| 4 |
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| 5 | #include <linux/slab.h>
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| 6 | #include <linux/completion.h>
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| 7 | #include <linux/sched/task.h>
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| 8 | #include <linux/sched/vhost_task.h>
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| 9 | #include <linux/sched/signal.h>
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| 10 |
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| 11 | enum vhost_task_flags {
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| 12 | VHOST_TASK_FLAGS_STOP,
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| 13 | };
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| 14 |
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| 15 | static int vhost_task_fn(void *data)
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| 16 | {
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| 17 | struct vhost_task *vtsk = data;
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| 18 | int ret;
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| 19 |
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| 20 | ret = vtsk->fn(vtsk->data);
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| 21 | complete(&vtsk->exited);
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| 22 | do_exit(ret);
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| 23 | }
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| 24 |
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| 25 | |
| 26 | * vhost_task_stop - stop a vhost_task
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| 27 | * @vtsk: vhost_task to stop
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| 28 | *
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| 29 | * Callers must call vhost_task_should_stop and return from their worker
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| 30 | * function when it returns true;
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| 31 |
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| 32 | void vhost_task_stop(struct vhost_task *vtsk)
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| 33 | {
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| 34 | pid_t pid = vtsk->task->pid;
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| 35 |
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| 36 | set_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags);
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| 37 | wake_up_process(vtsk->task);
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| 38 | |
| 39 | * Make sure vhost_task_fn is no longer accessing the vhost_task before
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| 40 | * freeing it below. If userspace crashed or exited without closing,
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| 41 | * then the vhost_task->task could already be marked dead so
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| 42 | * kernel_wait will return early.
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| 43 |
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| 44 | wait_for_completion(&vtsk->exited);
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| 45 | |
| 46 | * If we are just closing/removing a device and the parent process is
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| 47 | * not exiting then reap the task.
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| 48 |
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| 49 | kernel_wait4(pid, NULL, __WCLONE, NULL);
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| 50 | kfree(vtsk);
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| 51 | }
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| 52 | EXPORT_SYMBOL_GPL(vhost_task_stop);
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| 53 |
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| 54 | |
| 55 | * vhost_task_should_stop - should the vhost task return from the work function
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| 56 | * @vtsk: vhost_task to stop
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| 57 |
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| 58 | bool vhost_task_should_stop(struct vhost_task *vtsk)
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| 59 | {
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| 60 | return test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags);
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| 61 | }
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| 62 | EXPORT_SYMBOL_GPL(vhost_task_should_stop);
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| 63 |
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| 64 | |
| 65 | * vhost_task_create - create a copy of a process to be used by the kernel
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| 66 | * @fn: thread stack
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| 67 | * @arg: data to be passed to fn
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| 68 | * @name: the thread's name
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| 69 | *
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| 70 | * This returns a specialized task for use by the vhost layer or NULL on
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| 71 | * failure. The returned task is inactive, and the caller must fire it up
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| 72 | * through vhost_task_start().
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| 73 |
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| 74 | struct vhost_task *vhost_task_create(int (*fn)(void *), void *arg,
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| 75 | const char *name)
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| 76 | {
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| 77 | struct kernel_clone_args args = {
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| 78 | .flags = CLONE_FS | CLONE_UNTRACED | CLONE_VM,
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| 79 | .exit_signal = 0,
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| 80 | .fn = vhost_task_fn,
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| 81 | .name = name,
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| 82 | .user_worker = 1,
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| 83 | .no_files = 1,
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| 84 | .ignore_signals = 1,
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| 85 | };
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| 86 | struct vhost_task *vtsk;
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| 87 | struct task_struct *tsk;
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| 88 |
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| 89 | vtsk = kzalloc(sizeof(*vtsk), GFP_KERNEL);
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| 90 | if (!vtsk)
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| 91 | return NULL;
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| 92 | init_completion(&vtsk->exited);
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| 93 | vtsk->data = arg;
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| 94 | vtsk->fn = fn;
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| 95 |
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| 96 | args.fn_arg = vtsk;
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| 97 |
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| 98 | tsk = copy_process(NULL, 0, NUMA_NO_NODE, &args);
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| 99 | if (IS_ERR(tsk)) {
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| 100 | kfree(vtsk);
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| 101 | return NULL;
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| 102 | }
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| 103 |
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| 104 | vtsk->task = tsk;
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| 105 | return vtsk;
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| 106 | }
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| 107 | EXPORT_SYMBOL_GPL(vhost_task_create);
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| 108 |
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| 109 | |
| 110 | * vhost_task_start - start a vhost_task created with vhost_task_create
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| 111 | * @vtsk: vhost_task to wake up
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| 112 |
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| 113 | void vhost_task_start(struct vhost_task *vtsk)
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| 114 | {
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| 115 | wake_up_new_task(vtsk->task);
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| 116 | }
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| 117 | EXPORT_SYMBOL_GPL(vhost_task_start);
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