On 11/15/23 6:42 AM, Jens Axboe wrote:
> */
> has_lock = mutex_trylock(&ctx->uring_lock);
>
>- if (has_lock && (ctx->flags & IORING_SETUP_SQPOLL)) {
>- struct io_sq_data *sq = ctx->sq_data;
>-
>- sq_pid = sq->task_pid;
>- sq_cpu = sq->sq_cpu;
>+ if (ctx->flags & IORING_SETUP_SQPOLL) {
>+ struct io_sq_data *sq;
>+
>+ rcu_read_lock();
>+ sq = READ_ONCE(ctx->sq_data);
>+ if (sq) {
>+ sq_pid = sq->task_pid;
>+ sq_cpu = sq->sq_cpu;
>+ }
>+ rcu_read_unlock();
> }
>
> seq_printf(m, "SqThread:\t%d\n", sq_pid);
>diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c
>index 65b5dbe3c850..583c76945cdf 100644
>--- a/io_uring/sqpoll.c
>+++ b/io_uring/sqpoll.c
>@@ -70,7 +70,7 @@ void io_put_sq_data(struct io_sq_data *sqd)
> WARN_ON_ONCE(atomic_read(&sqd->park_pending));
>
> io_sq_thread_stop(sqd);
>- kfree(sqd);
>+ kfree_rcu(sqd, rcu);
> }
> }
>
>@@ -313,7 +313,7 @@ static int io_sq_thread(void *data)
> }
>
> io_uring_cancel_generic(true, sqd);
>- sqd->thread = NULL;
>+ WRITE_ONCE(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();
>@@ -411,7 +411,7 @@ __cold int io_sq_offload_create(struct io_ring_ctx *ctx,
> goto err_sqpoll;
> }
>
>- sqd->thread = tsk;
>+ WRITE_ONCE(sqd->thread, tsk);
> ret = io_uring_alloc_task_context(tsk, ctx);
> wake_up_new_task(tsk);
> if (ret)
>diff --git a/io_uring/sqpoll.h b/io_uring/sqpoll.h
>index 8df37e8c9149..0cf0c5833a27 100644
>--- a/io_uring/sqpoll.h
>+++ b/io_uring/sqpoll.h
>@@ -18,6 +18,8 @@ struct io_sq_data {
>
> unsigned long state;
> struct completion exited;
>+
>+ struct rcu_head rcu;
> };
>
> int io_sq_offload_create(struct io_ring_ctx *ctx, struct io_uring_params *p);
I tested this and it worked after adding RCU lock.
It consistently outputs correct results.
The results of a simple test are as follows:
Every 0.5s: cat /proc/10212/fdinfo/6 | grep Sq
SqMask: 0x3
SqHead: 17422716
SqTail: 17422716
CachedSqHead: 17422716
SqThread: 10212
SqThreadCpu: 73
SqBusy: 97%
-------------------------------------------------------------
But the name of the sq thread is "iou-sqp-" + "the PID of its parent process":
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
10211 root 20 0 184408 8192 0 R 99.9 0.0 4:01.42 fio
10212 root 20 0 184408 8192 0 R 99.9 0.0 4:01.48 iou-sqp-10211
Is this the originally desired effect?
