dm-bufio: don't schedule in atomic context

LongPing Wei · Mikulas Patocka · commit a3d8f0a7f5e8 · 2025-04-23T13:09:10.000+02:00
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: 7cd3267 ("dm bufio: remove dm_bufio_cond_resched()") Signed-off-by: LongPing Wei <weilongping@oppo.com> Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
diff --git 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
+
 /*--------------------------------------------------------------*/
 
 /*
@@ -2424,7 +2426,12 @@ 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);
+			}
 		}
 	}
 }

Original file line number	Diff line number	Diff line change
`@@ -68,6 +68,8 @@`
`68`	`68`	`#define LIST_DIRTY 1`
`69`	`69`	`#define LIST_SIZE 2`
`70`	`70`
	`71`	`+#define SCAN_RESCHED_CYCLE 16`
	`72`	`+`
`71`	`73`	`/--------------------------------------------------------------/`
`72`	`74`
`73`	`75`	`/*`
`@@ -2424,7 +2426,12 @@ static void __scan(struct dm_bufio_client *c)`
`2424`	`2426`
`2425`	`2427`	`atomic_long_dec(&c->need_shrink);`
`2426`	`2428`	`freed++;`
`2427`		`- cond_resched();`
	`2429`	`+`
	`2430`	`+ if (unlikely(freed % SCAN_RESCHED_CYCLE == 0)) {`
	`2431`	`+ dm_bufio_unlock(c);`
	`2432`	`+ cond_resched();`
	`2433`	`+ dm_bufio_lock(c);`
	`2434`	`+ }`
`2428`	`2435`	`}`
`2429`	`2436`	`}`
`2430`	`2437`	`}`