On 2019/1/24 4:09 下午, Junhui Tang wrote:
> From d75d1b51aeedcc9349571be084c5f51d8f7e7612 Mon Sep 17 00:00:00 2001
> From: Tang Junhui <tang.junhui.linux@xxxxxxxxx>
> Date: Thu, 24 Jan 2019 16:01:35 +0800
> Subject: [PATCH] bcache: fix a race between register and allocator thread
>
> when register a new cache device, allocator get stucked,
> the call trace is bellow:
> Sangfor:EDS/eds-fe5192de /sf # cat /proc/3642/task/*/stack
> [<ffffffffa02b01c8>] bch_bucket_alloc+0x178/0x2b0 [bcache]
> [<ffffffffa02c737d>] bch_prio_write+0x18d/0x320 [bcache]
> [<ffffffffa02b0042>] bch_allocator_thread+0x432/0x440 [bcache]
> [<ffffffff810a1430>] kthread+0xc0/0xd0
> [<ffffffff8173def7>] ret_from_fork+0x77/0xb0
> [<ffffffffffffffff>] 0xffffffffffffffff
>
> There is a race between register and allocator thread:
> register thread allocator thread
> run_cache_set
> =>bch_initial_gc_finish
> alloc prio buckets
> =>bch_cache_allocator_start
> start allocator thread bch_allocator_thread
> =>bch_prio_write =>invalidate_buckets
> write prio using prio buckets fill bucket into ca->free_inc
> =>SET_CACHE_SYNC
> set cache sync mode =>bch_prio_write
> since cache sync mode is set,
> write prio to bucket, and the
> prio bucket has been used in
> register thread, no bucket can
> used. so the allocator thread
> stuck here.
> In this patch, register thread wait for the allocator thread to finish
> work, then write prio to buckets and set cache to sync mode.
>
> Signed-off-by: Tang Junhui <tang.junhui.linux@xxxxxxxxx>
> ---
> drivers/md/bcache/super.c | 25 ++++++++++++++++++++-----
> 1 file changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index fa4058e..818d2f1 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -1852,13 +1852,28 @@ static void run_cache_set(struct cache_set *c)
> bch_initial_gc_finish(c);
>
> err = "error starting allocator thread";
> - for_each_cache(ca, c, i)
> - if (bch_cache_allocator_start(ca))
> - goto err;
> -
> mutex_lock(&c->bucket_lock);
> - for_each_cache(ca, c, i)
> + for_each_cache(ca, c, i) {
> + DEFINE_WAIT(wait);
> +
> + if (bch_cache_allocator_start(ca)) {
> + mutex_unlock(&c->bucket_lock);
> + goto err;
> + }
> +
> + for (;;) {
> + prepare_to_wait(&c->bucket_wait, &wait,
> + TASK_UNINTERRUPTIBLE);
> + if (!fifo_empty(&ca->free_inc))
> + break;
> + mutex_unlock(&c->bucket_lock);
> + schedule();
> + mutex_lock(&c->bucket_lock);
> + }
> +
> + finish_wait(&c->bucket_wait, &wait);
> bch_prio_write(ca);
> + }
> mutex_unlock(&c->bucket_lock);
>
> err = "cannot allocate new UUID bucket";
>
Hi Junhui,
It seems your patch losts all indent format. Could you please to handle
it and resend the peroper format again ?
Thanks.
--
Coly Li
