Thanks, I staged this patch for 6.15.
Mikulas
On Thu, 17 Apr 2025, LongPing Wei wrote:
> A BUG was reported as below when CONFIG_DEBUG_ATOMIC_SLEEP and
> try_verify_in_tasklet are enabled.
> [ 129.444685][ T934] BUG: sleeping function called from invalid context at
> drivers/md/dm-bufio.c:2421
> [ 129.444723][ T934] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid:
> 934, name: kworker/1:4
> [ 129.444740][ T934] preempt_count: 201, expected: 0
> [ 129.444756][ T934] RCU nest depth: 0, expected: 0
> [ 129.444781][ T934] Preemption disabled at:
> [ 129.444789][ T934] [<ffffffd816231900>] shrink_work+0x21c/0x248
> [ 129.445167][ T934] kernel BUG at kernel/sched/walt/walt_debug.c:16!
> [ 129.445183][ T934] Internal error: Oops - BUG: 00000000f2000800 [#1]
> PREEMPT SMP
> [ 129.445204][ T934] Skip md ftrace buffer dump for: 0x1609e0
> [ 129.447348][ T934] CPU: 1 PID: 934 Comm: kworker/1:4 Tainted: G W
> OE 6.6.56-android15-8-o-g6f82312b30b9-debug #1
> 1400000003000000474e5500b3187743670464e8
> [ 129.447362][ T934] Hardware name: Qualcomm Technologies, Inc. Parrot QRD,
> Alpha-M (DT)
> [ 129.447373][ T934] Workqueue: dm_bufio_cache shrink_work
> [ 129.447394][ T934] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS
> BTYPE=--)
> [ 129.447406][ T934] pc : android_rvh_schedule_bug+0x0/0x8
> [sched_walt_debug]
> [ 129.447435][ T934] lr : __traceiter_android_rvh_schedule_bug+0x44/0x6c
> [ 129.447451][ T934] sp : ffffffc0843dbc90
> [ 129.447459][ T934] x29: ffffffc0843dbc90 x28: ffffffffffffffff x27:
> 0000000000000c8b
> [ 129.447479][ T934] x26: 0000000000000040 x25: ffffff804b3d6260 x24:
> ffffffd816232b68
> [ 129.447497][ T934] x23: ffffff805171c5b4 x22: 0000000000000000 x21:
> ffffffd816231900
> [ 129.447517][ T934] x20: ffffff80306ba898 x19: 0000000000000000 x18:
> ffffffc084159030
> [ 129.447535][ T934] x17: 00000000d2b5dd1f x16: 00000000d2b5dd1f x15:
> ffffffd816720358
> [ 129.447554][ T934] x14: 0000000000000004 x13: ffffff89ef978000 x12:
> 0000000000000003
> [ 129.447572][ T934] x11: ffffffd817a823c4 x10: 0000000000000202 x9 :
> 7e779c5735de9400
> [ 129.447591][ T934] x8 : ffffffd81560d004 x7 : 205b5d3938373434 x6 :
> ffffffd8167397c8
> [ 129.447610][ T934] x5 : 0000000000000000 x4 : 0000000000000001 x3 :
> ffffffc0843db9e0
> [ 129.447629][ T934] x2 : 0000000000002f15 x1 : 0000000000000000 x0 :
> 0000000000000000
> [ 129.447647][ T934] Call trace:
> [ 129.447655][ T934] android_rvh_schedule_bug+0x0/0x8 [sched_walt_debug
> 1400000003000000474e550080cce8a8a78606b6]
> [ 129.447681][ T934] __might_resched+0x190/0x1a8
> [ 129.447694][ T934] shrink_work+0x180/0x248
> [ 129.447706][ T934] process_one_work+0x260/0x624
> [ 129.447718][ T934] worker_thread+0x28c/0x454
> [ 129.447729][ T934] kthread+0x118/0x158
> [ 129.447742][ T934] ret_from_fork+0x10/0x20
> [ 129.447761][ T934] Code: ???????? ???????? ???????? d2b5dd1f (d4210000)
> [ 129.447772][ T934] ---[ end trace 0000000000000000 ]---
>
> dm_bufio_lock will call spin_lock_bh when try_verify_in_tasklet
> is enabled, and __scan will be called in atomic context.
>
> Fixes: 7cd326747f46 ("dm bufio: remove dm_bufio_cond_resched()")
> Signed-off-by: LongPing Wei <[email protected]>
> Cc: [email protected]
> ---
> v3: Always drops the lock after every 16 iterations and
> calls cond_resched() with the lock dropped;
> Change the judgment condition to a more understandable way.
> v2: When no_sleep is enabled, drops the lock after every 16 iterations and
> calls
> cond_resched() with the lock dropped.
> v1: skip cond_resched when no_sleep is enabled
> ---
> drivers/md/dm-bufio.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
> index 9c8ed65cd87e..3088f9f9169a 100644
> --- a/drivers/md/dm-bufio.c
> +++ b/drivers/md/dm-bufio.c
> @@ -68,6 +68,8 @@
> #define LIST_DIRTY 1
> #define LIST_SIZE 2
>
> +#define SCAN_RESCHED_CYCLE 16
> +
> /*--------------------------------------------------------------*/
>
> /*
> @@ -2424,8 +2426,13 @@ static void __scan(struct dm_bufio_client *c)
>
> atomic_long_dec(&c->need_shrink);
> freed++;
> - cond_resched();
> - }
> +
> + if (unlikely(freed % SCAN_RESCHED_CYCLE == 0)) {
> + dm_bufio_unlock(c);
> + cond_resched();
> + dm_bufio_lock(c);
> + }
> + }
> }
> }
>
> --
> 2.34.1
>
