blob: 559652380672c08878264b9f9b17dc7ac831e12b [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
/*
* Contains the core associated with submission side polling of the SQ
* ring, offloading submissions from the application to a kernel thread.
*/
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/file.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/audit.h>
#include <linux/security.h>
#include <linux/io_uring.h>
#include <uapi/linux/io_uring.h>
#include "io_uring.h"
#include "sqpoll.h"
#define IORING_SQPOLL_CAP_ENTRIES_VALUE 8
enum {
IO_SQ_THREAD_SHOULD_STOP = 0,
IO_SQ_THREAD_SHOULD_PARK,
};
void io_sq_thread_unpark(struct io_sq_data *sqd)
__releases(&sqd->lock)
{
WARN_ON_ONCE(sqd->thread == current);
/*
* Do the dance but not conditional clear_bit() because it'd race with
* other threads incrementing park_pending and setting the bit.
*/
clear_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
if (atomic_dec_return(&sqd->park_pending))
set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
mutex_unlock(&sqd->lock);
}
void io_sq_thread_park(struct io_sq_data *sqd)
__acquires(&sqd->lock)
{
WARN_ON_ONCE(sqd->thread == current);
atomic_inc(&sqd->park_pending);
set_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state);
mutex_lock(&sqd->lock);
if (sqd->thread)
wake_up_process(sqd->thread);
}
void io_sq_thread_stop(struct io_sq_data *sqd)
{
WARN_ON_ONCE(sqd->thread == current);
WARN_ON_ONCE(test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state));
set_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
mutex_lock(&sqd->lock);
if (sqd->thread)
wake_up_process(sqd->thread);
mutex_unlock(&sqd->lock);
wait_for_completion(&sqd->exited);
}
void io_put_sq_data(struct io_sq_data *sqd)
{
if (refcount_dec_and_test(&sqd->refs)) {
WARN_ON_ONCE(atomic_read(&sqd->park_pending));
io_sq_thread_stop(sqd);
kfree(sqd);
}
}
static __cold void io_sqd_update_thread_idle(struct io_sq_data *sqd)
{
struct io_ring_ctx *ctx;
unsigned sq_thread_idle = 0;
list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
sq_thread_idle = max(sq_thread_idle, ctx->sq_thread_idle);
sqd->sq_thread_idle = sq_thread_idle;
}
void io_sq_thread_finish(struct io_ring_ctx *ctx)
{
struct io_sq_data *sqd = ctx->sq_data;
if (sqd) {
io_sq_thread_park(sqd);
list_del_init(&ctx->sqd_list);
io_sqd_update_thread_idle(sqd);
io_sq_thread_unpark(sqd);
io_put_sq_data(sqd);
ctx->sq_data = NULL;
}
}
static struct io_sq_data *io_attach_sq_data(struct io_uring_params *p)
{
struct io_ring_ctx *ctx_attach;
struct io_sq_data *sqd;
struct fd f;
f = fdget(p->wq_fd);
if (!f.file)
return ERR_PTR(-ENXIO);
if (!io_is_uring_fops(f.file)) {
fdput(f);
return ERR_PTR(-EINVAL);
}
ctx_attach = f.file->private_data;
sqd = ctx_attach->sq_data;
if (!sqd) {
fdput(f);
return ERR_PTR(-EINVAL);
}
if (sqd->task_tgid != current->tgid) {
fdput(f);
return ERR_PTR(-EPERM);
}
refcount_inc(&sqd->refs);
fdput(f);
return sqd;
}
static struct io_sq_data *io_get_sq_data(struct io_uring_params *p,
bool *attached)
{
struct io_sq_data *sqd;
*attached = false;
if (p->flags & IORING_SETUP_ATTACH_WQ) {
sqd = io_attach_sq_data(p);
if (!IS_ERR(sqd)) {
*attached = true;
return sqd;
}
/* fall through for EPERM case, setup new sqd/task */
if (PTR_ERR(sqd) != -EPERM)
return sqd;
}
sqd = kzalloc(sizeof(*sqd), GFP_KERNEL);
if (!sqd)
return ERR_PTR(-ENOMEM);
atomic_set(&sqd->park_pending, 0);
refcount_set(&sqd->refs, 1);
INIT_LIST_HEAD(&sqd->ctx_list);
mutex_init(&sqd->lock);
init_waitqueue_head(&sqd->wait);
init_completion(&sqd->exited);
return sqd;
}
static inline bool io_sqd_events_pending(struct io_sq_data *sqd)
{
return READ_ONCE(sqd->state);
}
static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
{
unsigned int to_submit;
int ret = 0;
to_submit = io_sqring_entries(ctx);
/* if we're handling multiple rings, cap submit size for fairness */
if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE)
to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE;
if (!wq_list_empty(&ctx->iopoll_list) || to_submit) {
const struct cred *creds = NULL;
if (ctx->sq_creds != current_cred())
creds = override_creds(ctx->sq_creds);
mutex_lock(&ctx->uring_lock);
if (!wq_list_empty(&ctx->iopoll_list))
io_do_iopoll(ctx, true);
/*
* Don't submit if refs are dying, good for io_uring_register(),
* but also it is relied upon by io_ring_exit_work()
*/
if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)) &&
!(ctx->flags & IORING_SETUP_R_DISABLED))
ret = io_submit_sqes(ctx, to_submit);
mutex_unlock(&ctx->uring_lock);
if (to_submit && wq_has_sleeper(&ctx->sqo_sq_wait))
wake_up(&ctx->sqo_sq_wait);
if (creds)
revert_creds(creds);
}
return ret;
}
static bool io_sqd_handle_event(struct io_sq_data *sqd)
{
bool did_sig = false;
struct ksignal ksig;
if (test_bit(IO_SQ_THREAD_SHOULD_PARK, &sqd->state) ||
signal_pending(current)) {
mutex_unlock(&sqd->lock);
if (signal_pending(current))
did_sig = get_signal(&ksig);
cond_resched();
mutex_lock(&sqd->lock);
}
return did_sig || test_bit(IO_SQ_THREAD_SHOULD_STOP, &sqd->state);
}
static int io_sq_thread(void *data)
{
struct io_sq_data *sqd = data;
struct io_ring_ctx *ctx;
unsigned long timeout = 0;
char buf[TASK_COMM_LEN];
DEFINE_WAIT(wait);
snprintf(buf, sizeof(buf), "iou-sqp-%d", sqd->task_pid);
set_task_comm(current, buf);
if (sqd->sq_cpu != -1)
set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu));
else
set_cpus_allowed_ptr(current, cpu_online_mask);
current->flags |= PF_NO_SETAFFINITY;
mutex_lock(&sqd->lock);
while (1) {
bool cap_entries, sqt_spin = false;
if (io_sqd_events_pending(sqd) || signal_pending(current)) {
if (io_sqd_handle_event(sqd))
break;
timeout = jiffies + sqd->sq_thread_idle;
}
cap_entries = !list_is_singular(&sqd->ctx_list);
list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
int ret = __io_sq_thread(ctx, cap_entries);
if (!sqt_spin && (ret > 0 || !wq_list_empty(&ctx->iopoll_list)))
sqt_spin = true;
}
if (io_run_task_work())
sqt_spin = true;
if (sqt_spin || !time_after(jiffies, timeout)) {
cond_resched();
if (sqt_spin)
timeout = jiffies + sqd->sq_thread_idle;
continue;
}
prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE);
if (!io_sqd_events_pending(sqd) && !task_work_pending(current)) {
bool needs_sched = true;
list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
atomic_or(IORING_SQ_NEED_WAKEUP,
&ctx->rings->sq_flags);
if ((ctx->flags & IORING_SETUP_IOPOLL) &&
!wq_list_empty(&ctx->iopoll_list)) {
needs_sched = false;
break;
}
/*
* Ensure the store of the wakeup flag is not
* reordered with the load of the SQ tail
*/
smp_mb__after_atomic();
if (io_sqring_entries(ctx)) {
needs_sched = false;
break;
}
}
if (needs_sched) {
mutex_unlock(&sqd->lock);
schedule();
mutex_lock(&sqd->lock);
}
list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
atomic_andnot(IORING_SQ_NEED_WAKEUP,
&ctx->rings->sq_flags);
}
finish_wait(&sqd->wait, &wait);
timeout = jiffies + sqd->sq_thread_idle;
}
io_uring_cancel_generic(true, sqd);
sqd->thread = NULL;
list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
atomic_or(IORING_SQ_NEED_WAKEUP, &ctx->rings->sq_flags);
io_run_task_work();
mutex_unlock(&sqd->lock);
complete(&sqd->exited);
do_exit(0);
}
int io_sqpoll_wait_sq(struct io_ring_ctx *ctx)
{
DEFINE_WAIT(wait);
do {
if (!io_sqring_full(ctx))
break;
prepare_to_wait(&ctx->sqo_sq_wait, &wait, TASK_INTERRUPTIBLE);
if (!io_sqring_full(ctx))
break;
schedule();
} while (!signal_pending(current));
finish_wait(&ctx->sqo_sq_wait, &wait);
return 0;
}
__cold int io_sq_offload_create(struct io_ring_ctx *ctx,
struct io_uring_params *p)
{
int ret;
/* Retain compatibility with failing for an invalid attach attempt */
if ((ctx->flags & (IORING_SETUP_ATTACH_WQ | IORING_SETUP_SQPOLL)) ==
IORING_SETUP_ATTACH_WQ) {
struct fd f;
f = fdget(p->wq_fd);
if (!f.file)
return -ENXIO;
if (!io_is_uring_fops(f.file)) {
fdput(f);
return -EINVAL;
}
fdput(f);
}
if (ctx->flags & IORING_SETUP_SQPOLL) {
struct task_struct *tsk;
struct io_sq_data *sqd;
bool attached;
ret = security_uring_sqpoll();
if (ret)
return ret;
sqd = io_get_sq_data(p, &attached);
if (IS_ERR(sqd)) {
ret = PTR_ERR(sqd);
goto err;
}
ctx->sq_creds = get_current_cred();
ctx->sq_data = sqd;
ctx->sq_thread_idle = msecs_to_jiffies(p->sq_thread_idle);
if (!ctx->sq_thread_idle)
ctx->sq_thread_idle = HZ;
io_sq_thread_park(sqd);
list_add(&ctx->sqd_list, &sqd->ctx_list);
io_sqd_update_thread_idle(sqd);
/* don't attach to a dying SQPOLL thread, would be racy */
ret = (attached && !sqd->thread) ? -ENXIO : 0;
io_sq_thread_unpark(sqd);
if (ret < 0)
goto err;
if (attached)
return 0;
if (p->flags & IORING_SETUP_SQ_AFF) {
int cpu = p->sq_thread_cpu;
ret = -EINVAL;
if (cpu >= nr_cpu_ids || !cpu_online(cpu))
goto err_sqpoll;
sqd->sq_cpu = cpu;
} else {
sqd->sq_cpu = -1;
}
sqd->task_pid = current->pid;
sqd->task_tgid = current->tgid;
tsk = create_io_thread(io_sq_thread, sqd, NUMA_NO_NODE);
if (IS_ERR(tsk)) {
ret = PTR_ERR(tsk);
goto err_sqpoll;
}
sqd->thread = tsk;
ret = io_uring_alloc_task_context(tsk, ctx);
wake_up_new_task(tsk);
if (ret)
goto err;
} else if (p->flags & IORING_SETUP_SQ_AFF) {
/* Can't have SQ_AFF without SQPOLL */
ret = -EINVAL;
goto err;
}
return 0;
err_sqpoll:
complete(&ctx->sq_data->exited);
err:
io_sq_thread_finish(ctx);
return ret;
}