linux-kernel - [PATCH 0/4] Fix scalability problem in workqueue watchdog touch caused by stop

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date: Tue, 25 Jun 2024 21:42:43 +1000
From: Nicholas Piggin <npiggin@...il.com>
To: Tejun Heo <tj@...nel.org>
Cc: Nicholas Piggin <npiggin@...il.com>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 0/4] Fix scalability problem in workqueue watchdog touch caused by stop_machine

Here are a few patches to fix a lockup caused by very slow progress due
to a scalability problem in workqueue watchdog touch being hammered by
thousands of CPUs in multi_cpu_stop. Patch 2 is the fix.

I did notice when making a microbenchmark reproducer that the RCU call
was actually also causing slowdowns. Not nearly so bad as the workqueue
touch, but workqueue queueing of dummy jobs slowed down by a factor of
several times when lots of other CPUs were making
rcu_momentary_dyntick_idle() calls. So I did the stop_machine patches to
reduce that. So those patches 3,4 are independent of the first two and
can go in any order.

Thanks,
Nick

Nicholas Piggin (4):
  workqueue: wq_watchdog_touch is always called with valid CPU
  workqueue: Improve scalability of workqueue watchdog touch
  stop_machine: Rearrange multi_cpu_stop state machine loop
  stop_machine: Add a delay between multi_cpu_stop touching watchdogs

 kernel/stop_machine.c | 31 +++++++++++++++++++++++--------
 kernel/workqueue.c    | 12 ++++++++++--
 2 files changed, 33 insertions(+), 10 deletions(-)

-- 
2.45.1