mirror of https://gitee.com/openkylin/linux.git
955dbdf4ce
Per-cpu workqueues have been tripping CPU affinity sanity checks while a CPU is being offlined. A per-cpu kworker ends up running on a CPU which isn't its target CPU while the CPU is online but inactive. While the scheduler allows kthreads to wake up on an online but inactive CPU, it doesn't allow a running kthread to be migrated to such a CPU, which leads to an odd situation where setting affinity on a sleeping and running kthread leads to different results. Each mem-reclaim workqueue has one rescuer which guarantees forward progress and the rescuer needs to bind itself to the CPU which needs help in making forward progress; however, due to the above issue, while set_cpus_allowed_ptr() succeeds, the rescuer doesn't end up on the correct CPU if the CPU is in the process of going offline, tripping the sanity check and executing the work item on the wrong CPU. This patch updates __migrate_task() so that kthreads can be migrated into an inactive but online CPU. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Reported-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> |
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README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.