Max Kellermann max.kellermann@ionos.com 于2025年9月12日周五 08:06写道：

Commit 88e6c42e40de ("io_uring/io-wq: add check free worker before create new worker") reused the variable `do_create` for something else, abusing it for the free worker check.

This caused the value to effectively always be `true` at the time `nr_workers < max_workers` was checked, but it should really be `false`. This means the `max_workers` setting was ignored, and worse: if the limit had already been reached, incrementing `nr_workers` was skipped even though another worker would be created.

When later lots of workers exit, the `nr_workers` field could easily underflow, making the problem worse because more and more workers would be created without incrementing `nr_workers`.

Thanks, my mistake. Reviewed-by: Fengnan Chang changfengnan@bytedance.com

The simple solution is to use a different variable for the free worker check instead of using one variable for two different things.

Cc: stable@vger.kernel.org Fixes: 88e6c42e40de ("io_uring/io-wq: add check free worker before create new worker") Signed-off-by: Max Kellermann max.kellermann@ionos.com

---

io_uring/io-wq.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index 17dfaa0395c4..1d03b2fc4b25 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -352,16 +352,16 @@ static void create_worker_cb(struct callback_head *cb) struct io_wq *wq;

    struct io_wq_acct *acct;

•   bool do_create = false;
  

•   bool activated_free_worker, do_create = false;
  
    worker = container_of(cb, struct io_worker, create_work);
    wq = worker->wq;
    acct = worker->acct;
  
    rcu_read_lock();
  

•   do_create = !io_acct_activate_free_worker(acct);
  

•   activated_free_worker = io_acct_activate_free_worker(acct);
    rcu_read_unlock();
  

•   if (!do_create)
  

•   if (activated_free_worker)
            goto no_need_create;
  
    raw_spin_lock(&acct->workers_lock);
  

-- 2.47.3