On 2023/12/3 9:23, Sergey Senozhatsky wrote:
On (23/12/02 23:50), Dongyun Liu wrote:
On 2023/12/1 23:39, Sergey Senozhatsky wrote:
On (23/11/30 23:20), Dongyun Liu wrote:
INFO: task init:331 blocked for more than 120 seconds. "echo 0 >
/proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:init state:D stack: 0 pid: 1 ppid: 0 flags:0x04000000
Call trace:
__switch_to+0x244/0x4e4
__schedule+0x5bc/0xc48
schedule+0x80/0x164
rwsem_down_read_slowpath+0x4fc/0xf9c
__down_read+0x140/0x188
down_read+0x14/0x24
try_wakeup_wbd_thread+0x78/0x1ec [zram]
__zram_bvec_write+0x720/0x878 [zram]
zram_bvec_rw+0xa8/0x234 [zram]
zram_submit_bio+0x16c/0x268 [zram]
submit_bio_noacct+0x128/0x3c8
submit_bio+0x1cc/0x3d0
__swap_writepage+0x5c4/0xd4c
swap_writepage+0x130/0x158
pageout+0x1f4/0x478
shrink_page_list+0x9b4/0x1eb8
shrink_inactive_list+0x2f4/0xaa8
shrink_lruvec+0x184/0x340
shrink_node_memcgs+0x84/0x3a0
shrink_node+0x2c4/0x6c4
shrink_zones+0x16c/0x29c
do_try_to_free_pages+0xe4/0x2b4
try_to_free_pages+0x388/0x7b4
__alloc_pages_direct_reclaim+0x88/0x278
__alloc_pages_slowpath+0x4ec/0xf6c
__alloc_pages_nodemask+0x1f4/0x3dc
kmalloc_order+0x54/0x338
kmalloc_order_trace+0x34/0x1bc
__kmalloc+0x5e8/0x9c0
kvmalloc_node+0xa8/0x264
backing_dev_store+0x1a4/0x818 [zram]
dev_attr_store+0x38/0x8c
sysfs_kf_write+0x64/0xc4
Hmm, I'm not really following this backtrace. Backing device
configuration is only possible on un-initialized zram device.
If it's uninitialized, then why is it being used for swapout
later in the call stack?
Uh, at this moment, zram has finished initializing and is
working. The backing device is an optional zram-based feature.
I think it can be created later.
backing_dev_store() can't be called on an initialized device,
that's what init_done() at the very beginning of backing_dev_store()
is supposed to ensure:
We have modified the logic here to allow backing_dev_store() to be
called multiple times. That's why the call trace comes in. On the other
hand, I realized that I should show the upstream's call stack instead
of my custom feature next time. Thank you for your toleration.
...
down_write(&zram->init_lock);
if (init_done(zram)) {
pr_info("Can't setup backing device for initialized device\n");
err = -EBUSY;
goto out;
}
...
