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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
e73f8959 ON |
2 | #include <linux/spinlock.h> |
3 | #include <linux/task_work.h> | |
4 | #include <linux/tracehook.h> | |
5 | ||
9da33de6 ON |
6 | static struct callback_head work_exited; /* all we need is ->next == NULL */ |
7 | ||
892f6668 ON |
8 | /** |
9 | * task_work_add - ask the @task to execute @work->func() | |
10 | * @task: the task which should run the callback | |
11 | * @work: the callback to run | |
91989c70 | 12 | * @notify: how to notify the targeted task |
892f6668 | 13 | * |
91989c70 JA |
14 | * Queue @work for task_work_run() below and notify the @task if @notify |
15 | * is @TWA_RESUME or @TWA_SIGNAL. @TWA_SIGNAL works like signals, in that the | |
16 | * it will interrupt the targeted task and run the task_work. @TWA_RESUME | |
17 | * work is run only when the task exits the kernel and returns to user mode, | |
18 | * or before entering guest mode. Fails if the @task is exiting/exited and thus | |
19 | * it can't process this @work. Otherwise @work->func() will be called when the | |
20 | * @task goes through one of the aforementioned transitions, or exits. | |
892f6668 | 21 | * |
91989c70 JA |
22 | * If the targeted task is exiting, then an error is returned and the work item |
23 | * is not queued. It's up to the caller to arrange for an alternative mechanism | |
24 | * in that case. | |
892f6668 | 25 | * |
91989c70 JA |
26 | * Note: there is no ordering guarantee on works queued here. The task_work |
27 | * list is LIFO. | |
c8219906 | 28 | * |
892f6668 ON |
29 | * RETURNS: |
30 | * 0 if succeeds or -ESRCH. | |
31 | */ | |
91989c70 JA |
32 | int task_work_add(struct task_struct *task, struct callback_head *work, |
33 | enum task_work_notify_mode notify) | |
e73f8959 | 34 | { |
ac3d0da8 | 35 | struct callback_head *head; |
9da33de6 | 36 | |
23f61f0f WW |
37 | /* record the work call stack in order to print it in KASAN reports */ |
38 | kasan_record_aux_stack(work); | |
39 | ||
ac3d0da8 | 40 | do { |
61e96496 | 41 | head = READ_ONCE(task->task_works); |
9da33de6 ON |
42 | if (unlikely(head == &work_exited)) |
43 | return -ESRCH; | |
ac3d0da8 ON |
44 | work->next = head; |
45 | } while (cmpxchg(&task->task_works, head, work) != head); | |
e73f8959 | 46 | |
e91b4816 | 47 | switch (notify) { |
91989c70 JA |
48 | case TWA_NONE: |
49 | break; | |
e91b4816 | 50 | case TWA_RESUME: |
e73f8959 | 51 | set_notify_resume(task); |
e91b4816 ON |
52 | break; |
53 | case TWA_SIGNAL: | |
03941ccf | 54 | set_notify_signal(task); |
e91b4816 | 55 | break; |
91989c70 JA |
56 | default: |
57 | WARN_ON_ONCE(1); | |
58 | break; | |
e91b4816 ON |
59 | } |
60 | ||
ed3e694d | 61 | return 0; |
e73f8959 ON |
62 | } |
63 | ||
892f6668 | 64 | /** |
c7aab1a7 | 65 | * task_work_cancel_match - cancel a pending work added by task_work_add() |
892f6668 | 66 | * @task: the task which should execute the work |
c7aab1a7 | 67 | * @match: match function to call |
892f6668 ON |
68 | * |
69 | * RETURNS: | |
70 | * The found work or NULL if not found. | |
71 | */ | |
67d12145 | 72 | struct callback_head * |
c7aab1a7 JA |
73 | task_work_cancel_match(struct task_struct *task, |
74 | bool (*match)(struct callback_head *, void *data), | |
75 | void *data) | |
e73f8959 | 76 | { |
ac3d0da8 | 77 | struct callback_head **pprev = &task->task_works; |
205e550a | 78 | struct callback_head *work; |
e73f8959 | 79 | unsigned long flags; |
61e96496 ON |
80 | |
81 | if (likely(!task->task_works)) | |
82 | return NULL; | |
ac3d0da8 ON |
83 | /* |
84 | * If cmpxchg() fails we continue without updating pprev. | |
85 | * Either we raced with task_work_add() which added the | |
86 | * new entry before this work, we will find it again. Or | |
9da33de6 | 87 | * we raced with task_work_run(), *pprev == NULL/exited. |
ac3d0da8 | 88 | */ |
e73f8959 | 89 | raw_spin_lock_irqsave(&task->pi_lock, flags); |
506458ef | 90 | while ((work = READ_ONCE(*pprev))) { |
c7aab1a7 | 91 | if (!match(work, data)) |
ac3d0da8 ON |
92 | pprev = &work->next; |
93 | else if (cmpxchg(pprev, work, work->next) == work) | |
94 | break; | |
e73f8959 | 95 | } |
e73f8959 | 96 | raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
ac3d0da8 ON |
97 | |
98 | return work; | |
e73f8959 ON |
99 | } |
100 | ||
c7aab1a7 JA |
101 | static bool task_work_func_match(struct callback_head *cb, void *data) |
102 | { | |
103 | return cb->func == data; | |
104 | } | |
105 | ||
106 | /** | |
107 | * task_work_cancel - cancel a pending work added by task_work_add() | |
108 | * @task: the task which should execute the work | |
109 | * @func: identifies the work to remove | |
110 | * | |
111 | * Find the last queued pending work with ->func == @func and remove | |
112 | * it from queue. | |
113 | * | |
114 | * RETURNS: | |
115 | * The found work or NULL if not found. | |
116 | */ | |
117 | struct callback_head * | |
118 | task_work_cancel(struct task_struct *task, task_work_func_t func) | |
119 | { | |
120 | return task_work_cancel_match(task, task_work_func_match, func); | |
121 | } | |
122 | ||
892f6668 ON |
123 | /** |
124 | * task_work_run - execute the works added by task_work_add() | |
125 | * | |
126 | * Flush the pending works. Should be used by the core kernel code. | |
127 | * Called before the task returns to the user-mode or stops, or when | |
128 | * it exits. In the latter case task_work_add() can no longer add the | |
129 | * new work after task_work_run() returns. | |
130 | */ | |
e73f8959 ON |
131 | void task_work_run(void) |
132 | { | |
133 | struct task_struct *task = current; | |
ac3d0da8 | 134 | struct callback_head *work, *head, *next; |
e73f8959 | 135 | |
ac3d0da8 | 136 | for (;;) { |
9da33de6 ON |
137 | /* |
138 | * work->func() can do task_work_add(), do not set | |
139 | * work_exited unless the list is empty. | |
140 | */ | |
141 | do { | |
6fb61492 | 142 | head = NULL; |
61e96496 | 143 | work = READ_ONCE(task->task_works); |
6fb61492 ON |
144 | if (!work) { |
145 | if (task->flags & PF_EXITING) | |
146 | head = &work_exited; | |
147 | else | |
148 | break; | |
149 | } | |
9da33de6 ON |
150 | } while (cmpxchg(&task->task_works, work, head) != work); |
151 | ||
ac3d0da8 ON |
152 | if (!work) |
153 | break; | |
6fb61492 ON |
154 | /* |
155 | * Synchronize with task_work_cancel(). It can not remove | |
156 | * the first entry == work, cmpxchg(task_works) must fail. | |
157 | * But it can remove another entry from the ->next list. | |
158 | */ | |
159 | raw_spin_lock_irq(&task->pi_lock); | |
160 | raw_spin_unlock_irq(&task->pi_lock); | |
e73f8959 | 161 | |
ac3d0da8 ON |
162 | do { |
163 | next = work->next; | |
164 | work->func(work); | |
165 | work = next; | |
f341861f | 166 | cond_resched(); |
ac3d0da8 | 167 | } while (work); |
e73f8959 ON |
168 | } |
169 | } |