On 11/17/23 8:19 PM, Xiaobing Li wrote:
> 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?
That's how it has always been, it's the sqpoll thread belonging to that
parent.
--
Jens Axboe
