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#1 2024-03-29 16:04:27

andreymal
Wiki Maintainer
Registered: 2014-02-02
Posts: 10

[SOLVED] Linux 6.8 hangs when using encrypted swap

After upgrading to Linux 6.8 (including the most recent 6.8.2.arch2-1), I noticed that the system hangs when swap is actively used.

My swap partition is encrypted with a random password as described in the wiki: https://wiki.archlinux.org/title/Dm-cry … sk_support

* I tried to use an unencrypted swap file on the same disk — the system does NOT hang (i.e. my disk is healthy and is probably not the cause of the hang).
* I tried to downgrade to linux 6.6.23-1-lts — the system does NOT hang.

Given these two facts, I suspect there is a bug in the 6.8 kernel, but I don't know how to properly describe and report it, so I decided to whine on this forum instead. Maybe people more knowledgeable than me can figure it out.

dmesg:

Mar 29 18:16:19 home kernel: INFO: task kswapd0:62 blocked for more than 122 seconds.
Mar 29 18:16:20 home kernel:       Tainted: P           OE      6.8.2-arch2-1 #1
Mar 29 18:16:38 home kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Mar 29 18:16:38 home kernel: task:kswapd0         state:D stack:0     pid:62    tgid:62    ppid:2      flags:0x00004000
Mar 29 18:16:38 home kernel: Call Trace:
Mar 29 18:16:38 home kernel:  <TASK>
Mar 29 18:16:39 home kernel:  __schedule+0x3e6/0x1520
Mar 29 18:16:39 home kernel:  schedule+0x32/0xd0
Mar 29 18:16:39 home kernel:  schedule_timeout+0x151/0x160
Mar 29 18:16:39 home kernel:  __down_common+0x14e/0x270
Mar 29 18:16:39 home kernel:  down+0x47/0x60
Mar 29 18:16:39 home kernel:  __map_bio+0xb6/0x1e0 [dm_mod 3b1a0d62406cfe5a1c5b69746e4723d34150ba76]
Mar 29 18:16:40 home kernel:  dm_submit_bio+0x1c3/0x580 [dm_mod 3b1a0d62406cfe5a1c5b69746e4723d34150ba76]
Mar 29 18:16:40 home kernel:  __submit_bio+0xb0/0x170
Mar 29 18:16:41 home kernel:  submit_bio_noacct_nocheck+0x159/0x370
Mar 29 18:16:41 home kernel:  ? submit_bio_noacct+0x49/0x580
Mar 29 18:16:41 home kernel:  zswap_writeback_entry+0xf2/0x180
Mar 29 18:16:42 home kernel:  shrink_memcg_cb+0xe7/0x2f0
Mar 29 18:16:42 home kernel:  ? xa_load+0x8c/0xe0
Mar 29 18:16:42 home kernel:  ? __pfx_shrink_memcg_cb+0x10/0x10
Mar 29 18:16:43 home kernel:  __list_lru_walk_one+0xb9/0x1d0
Mar 29 18:16:43 home kernel:  ? __pfx_shrink_memcg_cb+0x10/0x10
Mar 29 18:16:43 home kernel:  list_lru_walk_one+0x5d/0x90
Mar 29 18:16:44 home kernel:  zswap_shrinker_scan+0xc4/0x130
Mar 29 18:16:44 home kernel:  do_shrink_slab+0x13f/0x360
Mar 29 18:16:45 home kernel:  shrink_slab+0x28e/0x3c0
Mar 29 18:16:45 home kernel:  shrink_one+0x123/0x1b0
Mar 29 18:16:45 home kernel:  shrink_node+0x97e/0xbc0
Mar 29 18:16:46 home kernel:  balance_pgdat+0x523/0x960
Mar 29 18:16:46 home kernel:  ? __schedule+0x3ee/0x1520
Mar 29 18:16:47 home kernel:  ? __switch_to_asm+0x3e/0x70
Mar 29 18:16:47 home kernel:  kswapd+0x20d/0x400
Mar 29 18:16:48 home kernel:  ? __pfx_autoremove_wake_function+0x10/0x10
Mar 29 18:16:48 home kernel:  ? __pfx_kswapd+0x10/0x10
Mar 29 18:16:48 home kernel:  kthread+0xe5/0x120
Mar 29 18:16:49 home kernel:  ? __pfx_kthread+0x10/0x10
Mar 29 18:16:49 home kernel:  ret_from_fork+0x31/0x50
Mar 29 18:16:50 home kernel:  ? __pfx_kthread+0x10/0x10
Mar 29 18:16:50 home kernel:  ret_from_fork_asm+0x1b/0x30
Mar 29 18:16:51 home kernel:  </TASK>
Mar 29 18:16:51 home kernel: INFO: task kworker/u8:5:20255 blocked for more than 122 seconds.
Mar 29 18:16:51 home kernel:       Tainted: P           OE      6.8.2-arch2-1 #1
Mar 29 18:16:52 home kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Mar 29 18:16:52 home kernel: task:kworker/u8:5    state:D stack:0     pid:20255 tgid:20255 ppid:2      flags:0x00004000
Mar 29 18:16:52 home kernel: Workqueue: kcryptd/254:0 kcryptd_crypt [dm_crypt]
Mar 29 18:16:53 home kernel: Call Trace:
Mar 29 18:16:53 home kernel:  <TASK>
Mar 29 18:16:54 home kernel:  __schedule+0x3e6/0x1520
Mar 29 18:16:54 home kernel:  ? sysvec_apic_timer_interrupt+0xe/0x90
Mar 29 18:16:54 home kernel:  schedule+0x32/0xd0
Mar 29 18:16:55 home kernel:  schedule_preempt_disabled+0x15/0x30
Mar 29 18:16:55 home kernel:  __mutex_lock.constprop.0+0x39a/0x6a0
Mar 29 18:16:55 home kernel:  crypt_alloc_buffer+0x228/0x240 [dm_crypt 6f52c98e1f968012bd75812a29a17dce7ea3edc1]
Mar 29 18:16:56 home kernel:  kcryptd_crypt_write_convert+0x91/0x1e0 [dm_crypt 6f52c98e1f968012bd75812a29a17dce7ea3edc1]
Mar 29 18:16:56 home kernel:  process_one_work+0x183/0x370
Mar 29 18:16:56 home kernel:  worker_thread+0x3ab/0x4f0
Mar 29 18:16:57 home kernel:  ? __pfx_worker_thread+0x10/0x10
Mar 29 18:16:57 home kernel:  kthread+0xe5/0x120
Mar 29 18:16:57 home kernel:  ? __pfx_kthread+0x10/0x10
Mar 29 18:16:58 home kernel:  ret_from_fork+0x31/0x50
Mar 29 18:16:58 home kernel:  ? __pfx_kthread+0x10/0x10
Mar 29 18:16:58 home kernel:  ret_from_fork_asm+0x1b/0x30
Mar 29 18:16:58 home kernel:  </TASK>
Mar 29 18:16:58 home kernel: INFO: task kworker/u8:3:23688 blocked for more than 122 seconds.
Mar 29 18:16:59 home kernel:       Tainted: P           OE      6.8.2-arch2-1 #1
Mar 29 18:16:59 home kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Mar 29 18:16:59 home kernel: task:kworker/u8:3    state:D stack:0     pid:23688 tgid:23688 ppid:2      flags:0x00004000
Mar 29 18:17:00 home kernel: Workqueue: kcryptd/254:0 kcryptd_crypt [dm_crypt]
Mar 29 18:17:00 home kernel: Call Trace:
Mar 29 18:17:00 home kernel:  <TASK>
Mar 29 18:17:08 home kernel:  __schedule+0x3e6/0x1520
Mar 29 18:17:08 home kernel:  schedule+0x32/0xd0
Mar 29 18:17:08 home kernel:  schedule_preempt_disabled+0x15/0x30
Mar 29 18:17:08 home kernel:  __mutex_lock.constprop.0+0x39a/0x6a0
Mar 29 18:17:08 home kernel:  crypt_alloc_buffer+0x228/0x240 [dm_crypt 6f52c98e1f968012bd75812a29a17dce7ea3edc1]
Mar 29 18:17:08 home kernel:  kcryptd_crypt_write_convert+0x91/0x1e0 [dm_crypt 6f52c98e1f968012bd75812a29a17dce7ea3edc1]
Mar 29 18:17:08 home kernel:  process_one_work+0x183/0x370
Mar 29 18:17:08 home kernel:  worker_thread+0x3ab/0x4f0
Mar 29 18:17:08 home kernel:  ? __pfx_worker_thread+0x10/0x10
Mar 29 18:17:08 home kernel:  kthread+0xe5/0x120
Mar 29 18:17:08 home kernel:  ? __pfx_kthread+0x10/0x10
Mar 29 18:17:08 home kernel:  ret_from_fork+0x31/0x50
Mar 29 18:17:08 home kernel:  ? __pfx_kthread+0x10/0x10
Mar 29 18:17:08 home kernel:  ret_from_fork_asm+0x1b/0x30
Mar 29 18:17:08 home kernel:  </TASK>
Mar 29 18:17:08 home kernel: INFO: task kworker/u8:0:25663 blocked for more than 122 seconds.
Mar 29 18:17:08 home kernel:       Tainted: P           OE      6.8.2-arch2-1 #1
Mar 29 18:17:08 home kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Mar 29 18:17:08 home kernel: task:kworker/u8:0    state:D stack:0     pid:25663 tgid:25663 ppid:2      flags:0x00004000
Mar 29 18:17:08 home kernel: Workqueue: kcryptd/254:0 kcryptd_crypt [dm_crypt]
Mar 29 18:17:08 home kernel: Call Trace:
Mar 29 18:17:08 home kernel:  <TASK>
Mar 29 18:17:08 home kernel:  __schedule+0x3e6/0x1520
Mar 29 18:17:08 home kernel:  schedule+0x32/0xd0
Mar 29 18:17:08 home kernel:  schedule_timeout+0x151/0x160
Mar 29 18:17:08 home kernel:  __down_common+0x14e/0x270
Mar 29 18:17:08 home kernel:  down+0x47/0x60
Mar 29 18:17:08 home kernel:  __map_bio+0xb6/0x1e0 [dm_mod 3b1a0d62406cfe5a1c5b69746e4723d34150ba76]
Mar 29 18:17:09 home kernel:  dm_submit_bio+0x1c3/0x580 [dm_mod 3b1a0d62406cfe5a1c5b69746e4723d34150ba76]
Mar 29 18:17:09 home kernel:  __submit_bio+0xb0/0x170
Mar 29 18:17:09 home kernel:  submit_bio_noacct_nocheck+0x159/0x370
Mar 29 18:17:09 home kernel:  ? submit_bio_noacct+0x49/0x580
Mar 29 18:17:09 home kernel:  zswap_writeback_entry+0xf2/0x180
Mar 29 18:17:09 home kernel:  shrink_memcg_cb+0xe7/0x2f0
Mar 29 18:17:10 home kernel:  ? xa_load+0x8c/0xe0
Mar 29 18:17:10 home kernel:  ? __pfx_shrink_memcg_cb+0x10/0x10
Mar 29 18:17:10 home kernel:  __list_lru_walk_one+0xb9/0x1d0
Mar 29 18:17:10 home kernel:  ? __pfx_shrink_memcg_cb+0x10/0x10
Mar 29 18:17:10 home kernel:  list_lru_walk_one+0x5d/0x90
Mar 29 18:17:11 home kernel:  zswap_shrinker_scan+0xc4/0x130
Mar 29 18:17:11 home kernel:  do_shrink_slab+0x13f/0x360
Mar 29 18:17:11 home kernel:  shrink_slab+0x28e/0x3c0
Mar 29 18:17:11 home kernel:  shrink_one+0x123/0x1b0
Mar 29 18:17:11 home kernel:  shrink_node+0x97e/0xbc0
Mar 29 18:17:12 home kernel:  do_try_to_free_pages+0xe7/0x5b0
Mar 29 18:17:12 home kernel:  try_to_free_pages+0xe1/0x200
Mar 29 18:17:12 home kernel:  __alloc_pages_slowpath.constprop.0+0x343/0xde0
Mar 29 18:17:13 home kernel:  ? cbc_encrypt+0x97/0xd0 [aesni_intel 085fbf7cf52ecbd3eb6480274b7e7c625cd6073a]
Mar 29 18:17:13 home kernel:  __alloc_pages+0x32d/0x350
Mar 29 18:17:13 home kernel:  alloc_pages_mpol+0x95/0x1f0
Mar 29 18:17:14 home kernel:  ? bio_associate_blkg_from_css+0xf8/0x340
Mar 29 18:17:14 home kernel:  crypt_page_alloc+0x2e/0x60 [dm_crypt 6f52c98e1f968012bd75812a29a17dce7ea3edc1]
Mar 29 18:17:14 home kernel:  mempool_alloc+0x86/0x1b0
Mar 29 18:17:15 home kernel:  crypt_alloc_buffer+0x168/0x240 [dm_crypt 6f52c98e1f968012bd75812a29a17dce7ea3edc1]
Mar 29 18:17:15 home kernel:  kcryptd_crypt_write_convert+0x91/0x1e0 [dm_crypt 6f52c98e1f968012bd75812a29a17dce7ea3edc1]
Mar 29 18:17:15 home kernel:  process_one_work+0x183/0x370
Mar 29 18:17:16 home kernel:  worker_thread+0x3ab/0x4f0
Mar 29 18:17:16 home kernel:  ? __pfx_worker_thread+0x10/0x10
Mar 29 18:17:16 home kernel:  kthread+0xe5/0x120
Mar 29 18:17:16 home kernel:  ? __pfx_kthread+0x10/0x10
Mar 29 18:17:16 home kernel:  ret_from_fork+0x31/0x50
Mar 29 18:17:17 home kernel:  ? __pfx_kthread+0x10/0x10
Mar 29 18:17:17 home kernel:  ret_from_fork_asm+0x1b/0x30
Mar 29 18:17:17 home kernel:  </TASK>
Mar 29 18:17:17 home kernel: INFO: task kworker/u8:1:27614 blocked for more than 122 seconds.
Mar 29 18:17:18 home kernel:       Tainted: P           OE      6.8.2-arch2-1 #1
Mar 29 18:17:18 home kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
Mar 29 18:17:18 home kernel: task:kworker/u8:1    state:D stack:0     pid:27614 tgid:27614 ppid:2      flags:0x00004000
Mar 29 18:17:18 home kernel: Workqueue: kcryptd/254:0 kcryptd_crypt [dm_crypt]
Mar 29 18:17:19 home kernel: Call Trace:
Mar 29 18:17:19 home kernel:  <TASK>
Mar 29 18:17:19 home kernel:  __schedule+0x3e6/0x1520
Mar 29 18:17:19 home kernel:  schedule+0x32/0xd0
Mar 29 18:17:20 home kernel:  schedule_preempt_disabled+0x15/0x30
Mar 29 18:17:20 home kernel:  __mutex_lock.constprop.0+0x39a/0x6a0
Mar 29 18:17:20 home kernel:  crypt_alloc_buffer+0x228/0x240 [dm_crypt 6f52c98e1f968012bd75812a29a17dce7ea3edc1]
Mar 29 18:17:20 home kernel:  kcryptd_crypt_write_convert+0x91/0x1e0 [dm_crypt 6f52c98e1f968012bd75812a29a17dce7ea3edc1]
Mar 29 18:17:20 home kernel:  process_one_work+0x183/0x370
Mar 29 18:17:21 home kernel:  worker_thread+0x3ab/0x4f0
Mar 29 18:17:21 home kernel:  ? __pfx_worker_thread+0x10/0x10
Mar 29 18:17:21 home kernel:  kthread+0xe5/0x120
Mar 29 18:17:21 home kernel:  ? __pfx_kthread+0x10/0x10
Mar 29 18:17:22 home kernel:  ret_from_fork+0x31/0x50
Mar 29 18:17:22 home kernel:  ? __pfx_kthread+0x10/0x10
Mar 29 18:17:22 home kernel:  ret_from_fork_asm+0x1b/0x30
Mar 29 18:17:22 home kernel:  </TASK>

Last edited by andreymal (2024-04-14 20:17:18)

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#2 2024-03-29 22:08:04

seth
Member
Registered: 2012-09-03
Posts: 52,570

Re: [SOLVED] Linux 6.8 hangs when using encrypted swap

It starts w/ zswap writebacks, so you might want the check whether that's the issue, https://wiki.archlinux.org/title/Zswap#Toggling_zswap
Did you check whether an unencrypted swap /partition/ still works?

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#3 2024-03-29 23:24:03

andreymal
Wiki Maintainer
Registered: 2014-02-02
Posts: 10

Re: [SOLVED] Linux 6.8 hangs when using encrypted swap

With zswap disabled, it doesn't hang.
With an unencrypted swap partition, it doesn't hang (I just reused the same partition I use for encrypted swap).

So it seems that only the combination of zswap + encrypted swap causes it to hang

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#4 2024-04-01 21:00:05

seth
Member
Registered: 2012-09-03
Posts: 52,570

Re: [SOLVED] Linux 6.8 hangs when using encrypted swap

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#5 2024-04-05 01:11:57

andreymal
Wiki Maintainer
Registered: 2014-02-02
Posts: 10

Re: [SOLVED] Linux 6.8 hangs when using encrypted swap

Probably fixed in 6.8.3-arch1-1 (at least I can't manually trigger the hang). If it doesn't hang again, I'll mark this thread as solved

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#6 2024-04-14 20:17:27

andreymal
Wiki Maintainer
Registered: 2014-02-02
Posts: 10

Re: [SOLVED] Linux 6.8 hangs when using encrypted swap

6.8.5-arch1-1 doesn't hang, nice

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