This has been resolved with the following commits upstream:
commit d133166146333e1f13fc81c0e6c43c8d99290a8a
Author: Will Deacon <will.dea...@arm.com>
locking/qrwlock: Prevent slowpath writers getting held up by
fastpath
commit 087133ac90763cd339b6b67f2998f87dcc136c52
Author: Will Deacon <will.dea...@arm.com>
locking/qrwlock, arm64: Move rwlock implementation over to qrwlocks
commit b519b56e378ee82caf9b079b04f5db87dedc3251
Author: Will Deacon <will.dea...@arm.com>
locking/qrwlock: Use atomic_cond_read_acquire() when spinning in
qrwlock
commit 4df714be4dcf40bfb0d4af0f851a6e1977afa02e
Author: Will Deacon <will.dea...@arm.com>
locking/atomic: Add atomic_cond_read_acquire()
commit e0d02285f16e8d5810f3d5d5e8a5886ca0015d3b
Author: Will Deacon <will.dea...@arm.com>
locking/qrwlock: Use 'struct qrwlock' instead of 'struct __qrwlock
--
You received this bug notification because you are a member of Kernel
Packages, which is subscribed to linux in Ubuntu.
https://bugs.launchpad.net/bugs/1732238
Title:
arm64: Unfair rwlock can stall the system
Status in linux package in Ubuntu:
Confirmed
Status in linux source package in Artful:
Confirmed
Bug description:
[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
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