On 15/12/2020 11:42, Germano Massullo wrote: > Good day. I am investigating about a weird behavior of my system that > leads to frequent freezes. > The main components of my system are: Fedora 33 (kernel > 5.9.13-200.fc33.x86_64), cryptsetup 2.3.4, an AMD Ryzen 5 3600, 16 GB > RAM 3200 MHz, a Samsung 860 PRO used for 32 GB swap and LVM Cache, that > is encrypted with following criteria: > > # cryptsetup status ssd_cache > /dev/mapper/ssd_cache is active and is in use. > type: LUKS2 > cipher: aes-xts-plain64 > keysize: 512 bits > key location: keyring > device: /dev/sdc > sector size: 512 > offset: 32768 sectors > size: 500085424 sectors > mode: read/write > flags: discards > > During write bursts of swap (for example when booting some virtual > machines), the system completely freezes, I cannot even move the mouse > pointer. The system may remain in stuck state even for 10 minutes. When > the (host) system turns back to normal, I can see for example in virtual > machines, the following error in console > ======== > Message from syslogd@localhost at Dec 15 01:14:32 ... > kernel:watchdog: BUG: soft lockup - CPU#0 stuck for 124s! > [0x564a0d4baad0-:1924] > ======== > > To check if the complete stuck of the system was caused by encryption, I > tried to disable SSD swap, and create a unencrypted swap on a regular > HDD, and then when I had write bursts, the system slowed, but it did not > freeze. > How could I proceed in my investigation to find out if it is a matter of > system configuration, a bug, etc.? First, this is kernel issue, not a cryptsetup userspace issue (cryptsetup only configures kernel dm-crypt). With some encryption drivers that allocates memory during encryption there was a possible deadlock if swap is encrypted and system is out of memory. There should be a workaround in latest stable kernel that does not allow to use such crypto drivers in dm-crypt. For dm-crypt it is commit https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/md/dm-crypt.c?id=cd74693870fb748d812867ba49af733d689a3604 (but it requires also patches for crypto subsystem for setting this flag in drivers.) The long-term solution is to fix crypto drivers... Anyway, please try the latest stable kernel (ideally 5.10.x) - if you still see the problem, please report it to dm-devel@xxxxxxxxxx mailing list. (There is another patch that limits IOs in flight in dm-crypt, but this was not yet merged upstream - that could help too). Thanks, Milan _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx https://www.saout.de/mailman/listinfo/dm-crypt
