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