summaryrefslogtreecommitdiffstats
path: root/kernel/vhost_task.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/vhost_task.c')
-rw-r--r--kernel/vhost_task.c149
1 files changed, 149 insertions, 0 deletions
diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c
new file mode 100644
index 0000000000..da35e5b7f0
--- /dev/null
+++ b/kernel/vhost_task.c
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Oracle Corporation
+ */
+#include <linux/slab.h>
+#include <linux/completion.h>
+#include <linux/sched/task.h>
+#include <linux/sched/vhost_task.h>
+#include <linux/sched/signal.h>
+
+enum vhost_task_flags {
+ VHOST_TASK_FLAGS_STOP,
+};
+
+struct vhost_task {
+ bool (*fn)(void *data);
+ void *data;
+ struct completion exited;
+ unsigned long flags;
+ struct task_struct *task;
+};
+
+static int vhost_task_fn(void *data)
+{
+ struct vhost_task *vtsk = data;
+ bool dead = false;
+
+ for (;;) {
+ bool did_work;
+
+ if (!dead && signal_pending(current)) {
+ struct ksignal ksig;
+ /*
+ * Calling get_signal will block in SIGSTOP,
+ * or clear fatal_signal_pending, but remember
+ * what was set.
+ *
+ * This thread won't actually exit until all
+ * of the file descriptors are closed, and
+ * the release function is called.
+ */
+ dead = get_signal(&ksig);
+ if (dead)
+ clear_thread_flag(TIF_SIGPENDING);
+ }
+
+ /* mb paired w/ vhost_task_stop */
+ set_current_state(TASK_INTERRUPTIBLE);
+
+ if (test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags)) {
+ __set_current_state(TASK_RUNNING);
+ break;
+ }
+
+ did_work = vtsk->fn(vtsk->data);
+ if (!did_work)
+ schedule();
+ }
+
+ complete(&vtsk->exited);
+ do_exit(0);
+}
+
+/**
+ * vhost_task_wake - wakeup the vhost_task
+ * @vtsk: vhost_task to wake
+ *
+ * wake up the vhost_task worker thread
+ */
+void vhost_task_wake(struct vhost_task *vtsk)
+{
+ wake_up_process(vtsk->task);
+}
+EXPORT_SYMBOL_GPL(vhost_task_wake);
+
+/**
+ * vhost_task_stop - stop a vhost_task
+ * @vtsk: vhost_task to stop
+ *
+ * vhost_task_fn ensures the worker thread exits after
+ * VHOST_TASK_FLAGS_SOP becomes true.
+ */
+void vhost_task_stop(struct vhost_task *vtsk)
+{
+ set_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags);
+ vhost_task_wake(vtsk);
+ /*
+ * Make sure vhost_task_fn is no longer accessing the vhost_task before
+ * freeing it below.
+ */
+ wait_for_completion(&vtsk->exited);
+ kfree(vtsk);
+}
+EXPORT_SYMBOL_GPL(vhost_task_stop);
+
+/**
+ * vhost_task_create - create a copy of a task to be used by the kernel
+ * @fn: vhost worker function
+ * @arg: data to be passed to fn
+ * @name: the thread's name
+ *
+ * This returns a specialized task for use by the vhost layer or NULL on
+ * failure. The returned task is inactive, and the caller must fire it up
+ * through vhost_task_start().
+ */
+struct vhost_task *vhost_task_create(bool (*fn)(void *), void *arg,
+ const char *name)
+{
+ struct kernel_clone_args args = {
+ .flags = CLONE_FS | CLONE_UNTRACED | CLONE_VM |
+ CLONE_THREAD | CLONE_SIGHAND,
+ .exit_signal = 0,
+ .fn = vhost_task_fn,
+ .name = name,
+ .user_worker = 1,
+ .no_files = 1,
+ };
+ struct vhost_task *vtsk;
+ struct task_struct *tsk;
+
+ vtsk = kzalloc(sizeof(*vtsk), GFP_KERNEL);
+ if (!vtsk)
+ return NULL;
+ init_completion(&vtsk->exited);
+ vtsk->data = arg;
+ vtsk->fn = fn;
+
+ args.fn_arg = vtsk;
+
+ tsk = copy_process(NULL, 0, NUMA_NO_NODE, &args);
+ if (IS_ERR(tsk)) {
+ kfree(vtsk);
+ return NULL;
+ }
+
+ vtsk->task = tsk;
+ return vtsk;
+}
+EXPORT_SYMBOL_GPL(vhost_task_create);
+
+/**
+ * vhost_task_start - start a vhost_task created with vhost_task_create
+ * @vtsk: vhost_task to wake up
+ */
+void vhost_task_start(struct vhost_task *vtsk)
+{
+ wake_up_new_task(vtsk->task);
+}
+EXPORT_SYMBOL_GPL(vhost_task_start);