Hi,
On 12/08/2017 08:34 AM, Holger Hoffstätte wrote:
So plugging in a device on USB with BFQ as scheduler now works without
hiccup (probably thanks to Ming Lei's last patch), but of course I found
another problem. Unmounting the device after use, changing the scheduler
back to deadline or kyber and rmmod'ing the BFQ module reproducibly gives me:
kernel:
=============================================================================
kernel: BUG bfq_queue (Tainted: G B ): Objects remaining in
bfq_queue on __kmem_cache_shutdown()
kernel:
-----------------------------------------------------------------------------
kernel:
kernel: INFO: Slab 0xffffea001601fc00 objects=37 used=3 fp=0xffff8805807f0360
flags=0x8000000000008100
kernel: CPU: 0 PID: 9967 Comm: rmmod Tainted: G B 4.14.5 #1
kernel: Hardware name: Gigabyte Technology Co., Ltd. P67-DS3-B3/P67-DS3-B3,
BIOS F1 05/06/2011
kernel: Call Trace:
kernel: dump_stack+0x46/0x5e
kernel: slab_err+0x9e/0xb0
kernel: ? on_each_cpu_mask+0x35/0x40
kernel: ? ksm_migrate_page+0x60/0x60
kernel: ? __kmalloc+0x1c9/0x1d0
kernel: __kmem_cache_shutdown+0x177/0x350
kernel: shutdown_cache+0xf/0x130
kernel: kmem_cache_destroy+0x19e/0x1b0
kernel: SyS_delete_module+0x168/0x230
kernel: ? exit_to_usermode_loop+0x39/0x80
kernel: entry_SYSCALL_64_fastpath+0x13/0x94
kernel: RIP: 0033:0x7f53e4136b97
kernel: RSP: 002b:00007ffd660061d8 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
kernel: RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f53e4136b97
kernel: RDX: 000000000000000a RSI: 0000000000000800 RDI: 00000000006247f8
kernel: RBP: 0000000000000000 R08: 00007ffd66005171 R09: 0000000000000000
kernel: R10: 00007f53e41acbc0 R11: 0000000000000206 R12: 0000000000624790
kernel: R13: 00007ffd660051d0 R14: 0000000000624790 R15: 0000000000623260
kernel: INFO: Object 0xffff8805807f0000 @offset=0
kernel: INFO: Object 0xffff8805807f01b0 @offset=432
kernel: INFO: Object 0xffff8805807f3cc0 @offset=15552
kernel: kmem_cache_destroy bfq_queue: Slab cache still has objects
kernel: CPU: 0 PID: 9967 Comm: rmmod Tainted: G B 4.14.5 #1
kernel: Hardware name: Gigabyte Technology Co., Ltd. P67-DS3-B3/P67-DS3-B3,
BIOS F1 05/06/2011
kernel: Call Trace:
kernel: dump_stack+0x46/0x5e
kernel: kmem_cache_destroy+0x191/0x1b0
kernel: SyS_delete_module+0x168/0x230
kernel: ? exit_to_usermode_loop+0x39/0x80
kernel: entry_SYSCALL_64_fastpath+0x13/0x94
kernel: RIP: 0033:0x7f53e4136b97
kernel: RSP: 002b:00007ffd660061d8 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
kernel: RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f53e4136b97
kernel: RDX: 000000000000000a RSI: 0000000000000800 RDI: 00000000006247f8
kernel: RBP: 0000000000000000 R08: 00007ffd66005171 R09: 0000000000000000
kernel: R10: 00007f53e41acbc0 R11: 0000000000000206 R12: 0000000000624790
kernel: R13: 00007ffd660051d0 R14: 0000000000624790 R15: 0000000000623260
I also encountered the similar bug, seems there are some async objects
which are not freed with
BFQ_GROUP_IOSCHED build as "Y".
If revert part of commit e21b7a0b988772e82e7147e1c659a5afe2ae003c
("block, bfq: add full hierarchical
scheduling and cgroups support")like below, then I can't see the bug
again with simple test.
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 889a8549d97f..c640e64e042f 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4710,6 +4710,7 @@ static void bfq_exit_queue(struct elevator_queue *e)
spin_lock_irq(&bfqd->lock);
list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list)
bfq_deactivate_bfqq(bfqd, bfqq, false, false);
+ bfq_put_async_queues(bfqd, bfqd->root_group);
spin_unlock_irq(&bfqd->lock);
hrtimer_cancel(&bfqd->idle_slice_timer);
@@ -4718,7 +4719,6 @@ static void bfq_exit_queue(struct elevator_queue *e)
blkcg_deactivate_policy(bfqd->queue, &blkcg_policy_bfq);
#else
spin_lock_irq(&bfqd->lock);
- bfq_put_async_queues(bfqd, bfqd->root_group);
kfree(bfqd->root_group);
spin_unlock_irq(&bfqd->lock);
But perhaps we should do it inside blkcg_deactivate_policy, right?
Thanks,
Guoqing
