# US 11,029,968 B1 · Operating system with a single kernel stack per processor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,029,968 B1 - Document ID: US11029968B1 - Status: Granted - Kind: B1 - Application number: 16/528,221 - Filed: 2019-07-31 - Granted: 2021-06-08 - Earliest claimed: 2019-07-31 - Assignees: Facebook Technologies, LLC - Applicants: Facebook Technologies, LLC - Inventors: Christoph Klee; Bernhard Poess - Web page: https://patentgrep.com/patent/US11029968B1 ## CPC - G06F 9/4406: {Loading of operating system} - G06F 9/4881: {Scheduling strategies for dispatcher, e.g. round robin, multi-level priority queues} - G06F 9/4812: {by interrupt, e.g. masked} - G06F 9/5027: {the resource being a machine, e.g. CPUs, Servers, Terminals} - G06F 9/545: {where tasks reside in different layers, e.g. user- and kernel-space} - G06F 12/0875: with dedicated cache, e.g. instruction or stack - G06F 2212/1021: Hit rate improvement - G06F 2212/1028: Power efficiency - Y02D 10/00: Energy efficient computing, e.g. low power processors, power management or thermal management - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) - Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE ## Abstract In one embodiment, a method includes storing thread state information associated with the first user-mode thread into a memory space associated with the first user-mode thread when executing in kernel space in response to a first system call by a first-user mode thread, executing first operations corresponding to the first system call on a processor, where data associated with executing the first operations are stored on a kernel stack associated with the processor, determining to pause the execution of the first operations, enqueuing a workload on a schedule queue for resuming execution of the first operations in a future, where the workload comprises data associated with executing a remainder of the first operations, and executing second operations corresponding to a second system call from a second user-mode thread on the processor, where data associated with executing the second operations are stored on the kernel stack associated with the processor. ## Claims ### Claim 1 A method comprising, by a kernel-mode thread of an operating system of a computing device: storing, in response to a first system call by a first-user mode thread, thread state information associated with the first user-mode thread into a memory space associated with the first user-mode thread when executing in kernel space; executing, on a processor of the computing device, first operations corresponding to the first system call, wherein data associated with executing the first operations are stored on a kernel stack associated with the processor; determining to pause the execution of the first operations; enqueuing a workload on a schedule queue for resuming the execution of the first operations in a future, wherein the workload comprises data associated with executing a remainder of the first operations; and executing, on the processor, second operations corresponding to a second system call from a second user-mode thread, wherein data associated with executing the second operations are stored on the kernel stack associated with the processor. ### Claim 2 (depends on 1) The method of claim 1, wherein the thread state information associated with the first user-mode thread is a snapshot of register values associated with the processor when the first user-mode thread makes the first system call. ### Claim 3 (depends on 1) The method of claim 1, wherein the processor is associated with only one kernel-mode thread. ### Claim 4 (depends on 1) The method of claim 1, wherein the memory space associated with the first user-mode thread is a Thread-Local Storage (TLS) associated with the first user-mode thread. ### Claim 5 (depends on 1) The method of claim 1, wherein the memory space associated with the first user-mode thread is a Thread Control Block (TCB) associated with the first user-mode thread. ### Claim 6 (depends on 1) The method of claim 1, wherein determining to pause the execution of the first operations comprises calling a scheduler function, wherein the scheduler function makes a schedule decision among a plurality of workloads in the schedule queue. ### Claim 7 (depends on 6) The method of claim 6, wherein the schedule decision is made based on one or more scheduling policies. ### Claim 8 (depends on 1) The method of claim 1, wherein the second operations comprise returning to the second user-mode thread. ### Claim 9 (depends on 8) The method of claim 8, wherein returning to the second user-mode thread comprises: retrieving thread state information associated with the second user-mode thread from a memory space associated with the second user-mode thread; returning results of the second operations to the second system call; and restoring registers of the processor with the retrieved thread state information. ### Claim 10 (depends on 1) The method of claim 1, wherein the operating system is a microkernel-based operating system, wherein user-mode threads in the operating system comprise user application threads and service-providing threads. ### Claim 11 (depends on 10) The method of claim 10, wherein a first service-providing thread provides a particular service to second threads, wherein the second threads comprise other service-providing threads or user application threads. ### Claim 12 (depends on 11) The method of claim 11, wherein a request for the particular service from one of the second threads to the first service-providing thread is communicated through one of available Inter-Process Communication (IPC) mechanisms. ### Claim 13 (depends on 11) The method of claim 11, wherein a result of the particular service from the first service-providing thread to one of the second threads is communicated through one of available IPC mechanisms or a shared memory. ### Claim 14 (depends on 10) The method of claim 10, wherein the service-providing threads comprise device drivers. ### Claim 15 (depends on 10) The method of claim 10, wherein the user application threads are implemented with an event-driven architecture. ### Claim 16 One or more computer-readable non-transitory storage media embodying software that is operable by a kernel-mode thread of an operating system of a computing device when executed to: store, in response to a first system call by a first user-mode thread, thread state information associated with the first user-mode thread into a memory space associated with the first user-mode thread when executing in kernel space; execute, on a processor of the computing device, first operations corresponding to the first system call, wherein data associated with executing the first operations are stored on a kernel stack associated with the processor; determine to pause the execution of the first operations; enqueue a workload on a schedule queue for resuming the execution of the first operations in a future, wherein the workload comprises data associated with executing a remainder of the first operations; and execute, on the processor, second operations corresponding to a second system call from a second user-mode thread, wherein data associated with executing the second operations are stored on the kernel stack associated with the processor. ### Claim 17 (depends on 16) The media of claim 16, wherein the thread state information associated with the first user-mode thread is a snapshot of register values associated with the processor when the first user-mode thread makes the first system call. ### Claim 18 (depends on 16) The media of claim 16, wherein the processor is associated with only one kernel-mode thread. ### Claim 19 (depends on 16) The media of claim 16, wherein the memory space associated with the first user-mode thread is a Thread-Local Storage (TLS) associated with the first user-mode thread. ### Claim 20 A system comprising: one or more processors; and one or more computer-readable non-transitory storage media coupled to one or more of the processors and comprising instructions operable when executed by one of the processors to cause a kernel-mode thread of an operating system of the system to: store, in response to a first system call by a first user-mode thread, thread state information associated with the first user-mode thread into a memory space associated with the first user-mode thread when executing in kernel space; execute, on a processor among the one or more processors, first operations corresponding to the first system call, wherein data associated with executing the first operations are stored on a kernel stack associated with the processor; determine to pause the execution of the first operations; enqueue a workload on a schedule queue for resuming the execution of the first operations in a future, wherein the workload comprises data associated with executing a remainder of the first operations; and execute, on the processor, second operations corresponding to a second system call from a second user-mode thread, wherein data associated with executing the second operations are stored on the kernel stack associated with the processor.