On 10/26/21 4:32 AM, Muchun Song wrote: > On Tue, Oct 26, 2021 at 11:23 AM Zqiang <qiang.zhang1211@xxxxxxxxx> wrote: >> >> Due to raw_spin_lock/unlock() contains preempt_disable/enable() action, >> already regarded as RCU critical region, so remove unnecessary >> rcu_read_lock/unlock(). >> >> Signed-off-by: Zqiang <qiang.zhang1211@xxxxxxxxx> >> --- >> fs/io-wq.c | 2 -- >> 1 file changed, 2 deletions(-) >> >> diff --git a/fs/io-wq.c b/fs/io-wq.c >> index cd88602e2e81..401be005d089 100644 >> --- a/fs/io-wq.c >> +++ b/fs/io-wq.c >> @@ -855,9 +855,7 @@ static void io_wqe_enqueue(struct io_wqe *wqe, struct io_wq_work *work) >> io_wqe_insert_work(wqe, work); >> clear_bit(IO_ACCT_STALLED_BIT, &acct->flags); >> >> - rcu_read_lock(); > > Add a comment like: > /* spin_lock can serve as an RCU read-side critical section. */ Note that it's a raw spinlock. Honestly I'd probably prefer if we just leave it as-is. There are plans to improve the io-wq locking, and a rcu lock/unlock is pretty cheap. That said, if resend with a comment fully detailing why it's OK currently, then I'd be fine with that as well. -- Jens Axboe
