[lttng-dev] urcu workqueue thread uses 99% of cpu while workqueue is empty

Minlan Wang wangminlan at szsandstone.com
Thu Jun 16 03:09:44 EDT 2022

Hi, Mathieu,
We updated our kernel as your guide, now it's 3.10.0-1160.66.1.el7.x86_64, and
the issue still exists.

On Wed, Jun 15, 2022 at 10:15:58AM -0400, Mathieu Desnoyers wrote:
> ----- On Jun 14, 2022, at 11:49 PM, Minlan Wang wangminlan at szsandstone.com wrote:
> One more thing: did you apply any changes on top of the v0.12.1 userspace rcu tag ?
We make no change into the userspace-rcu-latest-0.12.tar.bz2 tarball, we just
place the extracted directory into our code repository.

> Also, can you provide the output of "./configure" on your system ? I'm also interested
> in knowing the contents of include/urcu/config.h after building liburcu.
This is the Makefile we use to build urcu:
CUR_DIR = $(shell pwd)
TOP_DIR = $(abspath $(CUR_DIR)/../)
URCU_DIR = $(abspath $(TOP_DIR)/thirdparty/usr)

	cd $(TOP_DIR)/thirdparty &&	\
	cd userspace-rcu-0.12.1	&& \
	export CFLAGS="-fPIC -g -O0" && \
	./configure --prefix=$(URCU_DIR) && \
	make				&& \
	make install			&& \
	cp src/workqueue.h $(URCU_DIR)/include/urcu/

I put the these things into the attachment config.tar.gz:
1. configure: the configure script under userspace-rcu-0.12.1/
2. config.log: the configure log after urcu build
3. config.h: include/urcu/config.h after building
4. Makefile: the Makefile recipe we use to build urcu

Thanks for your help,
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