On 2021-08-04 09:39:30 [-0600], Jens Axboe wrote:
> I'm confused, the waitqueue locks are always IRQ disabling.
spin_lock_irq() does not disable interrupts on -RT. The patch above
produces:
| BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:35
| in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 2020, name: iou-wrk-2018
| 1 lock held by iou-wrk-2018/2020:
| #0: ffff888111a47de8 (&hash->wait){+.+.}-{0:0}, at: io_worker_handle_work+0x443/0x630
| irq event stamp: 10
| hardirqs last enabled at (9): [<ffffffff81c47818>] _raw_spin_unlock_irqrestore+0x28/0x70
| hardirqs last disabled at (10): [<ffffffff81c4769e>] _raw_spin_lock_irq+0x3e/0x40
| softirqs last enabled at (0): [<ffffffff81077238>] copy_process+0x8f8/0x2020
| softirqs last disabled at (0): [<0000000000000000>] 0x0
| CPU: 5 PID: 2020 Comm: iou-wrk-2018 Tainted: G W 5.14.0-rc4-rt4+ #97
| Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
| Call Trace:
| dump_stack_lvl+0x45/0x59
| ___might_sleep.cold+0xa6/0xb6
| rt_spin_lock+0x35/0xc0
| ? io_worker_handle_work+0x443/0x630
| io_worker_handle_work+0x443/0x630
| io_wqe_worker+0xb4/0x340
| ? lockdep_hardirqs_on_prepare+0xd4/0x170
| ? _raw_spin_unlock_irqrestore+0x28/0x70
| ? _raw_spin_unlock_irqrestore+0x28/0x70
| ? io_worker_handle_work+0x630/0x630
| ? rt_mutex_slowunlock+0x2ba/0x310
| ? io_worker_handle_work+0x630/0x630
| ret_from_fork+0x22/0x30
But indeed, you are right, my snippet breaks non-RT. So this then maybe:
diff --git a/fs/io-wq.c b/fs/io-wq.c
index 57d3cdddcdb3e..0b931ac3c83e6 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -384,7 +384,7 @@ static void io_wait_on_hash(struct io_wqe *wqe, unsigned int hash)
{
struct io_wq *wq = wqe->wq;
- spin_lock(&wq->hash->wait.lock);
+ spin_lock_irq(&wq->hash->wait.lock);
if (list_empty(&wqe->wait.entry)) {
__add_wait_queue(&wq->hash->wait, &wqe->wait);
if (!test_bit(hash, &wq->hash->map)) {
@@ -392,7 +392,7 @@ static void io_wait_on_hash(struct io_wqe *wqe, unsigned int hash)
list_del_init(&wqe->wait.entry);
}
}
- spin_unlock(&wq->hash->wait.lock);
+ spin_unlock_irq(&wq->hash->wait.lock);
}
static struct io_wq_work *io_get_next_work(struct io_wqe *wqe)
@@ -430,9 +430,9 @@ static struct io_wq_work *io_get_next_work(struct io_wqe *wqe)
}
if (stall_hash != -1U) {
- raw_spin_unlock(&wqe->lock);
+ raw_spin_unlock_irq(&wqe->lock);
io_wait_on_hash(wqe, stall_hash);
- raw_spin_lock(&wqe->lock);
+ raw_spin_lock_irq(&wqe->lock);
}
return NULL;
(this is on-top of the patch you sent earlier and Daniel Cc: me on after
I checked that the problem/warning still exists).
Sebastian
