** Description changed: [Impact] There is a long-standing upstream bug with the ARM64 specific implementation of RW locks. The implementation can starve writers under lock contention leading to RCU stalls, driver timeouts and general system instability. [Test Case] $ stress-ng --kill 0 -t 300 -v You'll see the console fill with messages like: [ 2534.423119] INFO: rcu_sched detected stalls on CPUs/tasks: [ 2534.428606] 192-...: (1 ticks this GP) idle=b6e/140000000000000/0 softirq=578/578 fqs=6770 [ 2534.437029] (detected by 0, t=15005 jiffies, g=1479, c=1478, q=473) [ 2714.623691] INFO: rcu_sched detected stalls on CPUs/tasks: [ 2714.629181] 192-...: (1 ticks this GP) idle=b6e/140000000000000/0 softirq=578/578 fqs=12819 [ 2714.637692] (detected by 116, t=60058 jiffies, g=1479, c=1478, q=1736) [ 2747.216955] watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [kworker/0:5:1464] [ 2775.399061] watchdog: BUG: soft lockup - CPU#13 stuck for 123s! [systemd-network:2936] [Regression Risk] - TBD + The proposed fix for this comprises clean cherry-picks from the v4.15 merge window. The code modified for this fix is restricted to x86 & arm64, as they are the only Ubuntu architectures that define ARCH_USE_QUEUED_LOCKS. Fix verified on a 228 CPU arm64 (ThunderX2) server and regression tested on a 128-cpu x86 system using stress-ng and locktorture.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1732238 Title: arm64: Unfair rwlock can stall the system To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1732238/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
