Public bug reported:
[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 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
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1732238
Title:
arm64: Unfair rwlock can stall the system
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