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// 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,
VHOST_TASK_FLAGS_KILLED,
};
struct vhost_task {
bool (*fn)(void *data);
void (*handle_sigkill)(void *data);
void *data;
struct completion exited;
unsigned long flags;
struct task_struct *task;
/* serialize SIGKILL and vhost_task_stop calls */
struct mutex exit_mutex;
};
static int vhost_task_fn(void *data)
{
struct vhost_task *vtsk = data;
for (;;) {
bool did_work;
if (signal_pending(current)) {
struct ksignal ksig;
if (get_signal(&ksig))
break;
}
/* 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();
}
mutex_lock(&vtsk->exit_mutex);
/*
* If a vhost_task_stop and SIGKILL race, we can ignore the SIGKILL.
* When the vhost layer has called vhost_task_stop it's already stopped
* new work and flushed.
*/
if (!test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags)) {
set_bit(VHOST_TASK_FLAGS_KILLED, &vtsk->flags);
vtsk->handle_sigkill(vtsk->data);
}
mutex_unlock(&vtsk->exit_mutex);
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_STOP becomes true.
*/
void vhost_task_stop(struct vhost_task *vtsk)
{
mutex_lock(&vtsk->exit_mutex);
if (!test_bit(VHOST_TASK_FLAGS_KILLED, &vtsk->flags)) {
set_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags);
vhost_task_wake(vtsk);
}
mutex_unlock(&vtsk->exit_mutex);
/*
* 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
* @handle_sigkill: vhost function to handle when we are killed
* @arg: data to be passed to fn and handled_kill
* @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 (*handle_sigkill)(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);
mutex_init(&vtsk->exit_mutex);
vtsk->data = arg;
vtsk->fn = fn;
vtsk->handle_sigkill = handle_sigkill;
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);
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