# Re: raid1 resync stuck

- From: Jes Sorensen \<hidden\>
- Date: 2015-09-09 19:48:45 
- List: linux-raid
- Page: https://ratatoskr.run/linux-raid/2015/09/6630345
- Thread: https://ratatoskr.run/linux-raid/2015/09/6630345/t.md

```text
Jes Sorensen [ref] writes:
> Neil,
>
> We're chasing a case where the raid1 code gets stuck during resync. Nate
> is able to reproduce it much more reliably than me - so attaching his
> reproducing script. Basically run it on an existing raid1 with internal
> bitmap on rotating disk.
>
> Nate was able to bisect it to 79ef3a8aa1cb1523cc231c9a90a278333c21f761,
> the original iobarrier rewrite patch, and it can be reproduced in
> current Linus' top of trunk a794b4f3292160bb3fd0f1f90ec8df454e3b17b3.
>
> In Nate's analysis it hangs in raise_barrier():
>
> static void raise_barrier(struct r1conf *conf, sector_t sector_nr)
> {
> 	spin_lock_irq(&conf->resync_lock);
>
> 	/* Wait until no block IO is waiting */
> 	wait_event_lock_irq(conf->wait_barrier, !conf->nr_waiting,
> 			    conf->resync_lock);
>
> 	/* block any new IO from starting */
> 	conf->barrier++;
> 	conf->next_resync = sector_nr;
>
> 	/* For these conditions we must wait:
> 	 * A: while the array is in frozen state
> 	 * B: while barrier >= RESYNC_DEPTH, meaning resync reach
> 	 *    the max count which allowed.
> 	 * C: next_resync + RESYNC_SECTORS > start_next_window, meaning
> 	 *    next resync will reach to the window which normal bios are
> 	 *    handling.
> 	 * D: while there are any active requests in the current window.
> 	 */
> 	wait_event_lock_irq(conf->wait_barrier,
> 			    !conf->array_frozen &&
> 			    conf->barrier < RESYNC_DEPTH &&
> 			    conf->current_window_requests == 0 &&
> 			    (conf->start_next_window >=
> 			     conf->next_resync + RESYNC_SECTORS),
> 			    conf->resync_lock);
>
> crash> r1conf 0xffff882028f3e600 | grep -e array_frozen -e barrier -e start_next_window -e next_resync
>   barrier = 0x1,                      (conf->barrier < RESYNC_DEPTH)
>   array_frozen = 0x0,                 (!conf->array_frozen)
>   next_resync = 0x3000,
>   start_next_window = 0x3000,
>
> ie. next_resync == start_next_window, which will never wake up since
> start_next_window is smaller than next_resync + RESYNC_SECTORS.
>
> Have you seen anything like this?
>
> Cheers,
> Jes

Grrr - doing too many things in parallel :( I knew I forgot something -
here is Nate's script.

Jes
```

## Attachments

- [md\_stuck\_resync.sh](https://ratatoskr.run/linux-raid/2015/09/6630345/attachment/0) (text/plain, 1201 bytes)