This series introduces threads and uses them to improve the performance of the USB bus scanning code and to implement background jobs in the shell via two new commands: 'spawn' and 'wait'.
The threading framework is called 'uthread' and is inspired from the barebox threads [2]. setjmp() and longjmp() are used to save and restore contexts, as well as a non-standard extension called initjmp(). This new function is added in several patches, one for each architecture that supports HAVE_SETJMP. A new symbol is defined: HAVE_INITJMP. Two tests, one for initjmp() and one for the uthread scheduling, are added to the lib suite. After introducing threads and making schedule() and udelay() a thread re-scheduling point, the USB stack initialization is modified to benefit from concurrency when UTHREAD is enabled, where uthreads are used in usb_init() to initialize and scan multiple busses at the same time. The code was tested on arm64 and arm QEMU with 4 simulated XHCI buses and some devices. On this platform the USB scan takes 2.2 s instead of 5.6 s. Tested on i.MX93 EVK with two USB hubs, one ethernet adapter and one webcam on each, "usb start" takes 2.4 s instead of 4.6 s. Finally, the spawn and wait commands are introduced, allowing the use of threads from the shell. Tested on the i.MX93 EVK with a spinning HDD connected to USB1 and the network connected to ENET1. The USB plus DHCP init sequence "spawn usb start; spawn dhcp; wait" takes 4.5 seconds instead of 8 seconds for "usb start; dhcp". [1] https://patchwork.ozlabs.org/project/uboot/list/?series=446674 [2] https://github.com/barebox/barebox/blob/master/common/bthread.c Changes in v4: - Rebase on top of next (at 0e1fc465fea "Merge tag 'dm-pull-15mar25' of git://git.denx.de/u-boot-dm into next") - Add a stack_sz parameter to initjmp(). This is made necessary by the sandbox implementation which relies on sigaltstack(), which need both the stack base address and its size in its stack_t argument. In any case it is cleaner to provide the exact stack boundaries. With that, a crash was fixed on sandbox in the lib_initjmp unit test. @Ilias: I kept your R-b on the two patches with a trivial change (passing one more parameter), but I removed it from "arm: add initjmp()" since there's one more line of assembly code and who knows what I might have done wrong ;) - Remove symbol UTHREAD_GRANULARITY and use a tight scheduling loop in delay() instead. Tests on an i.MX93 board have shown that setting UTHREAD_GRANULARITY as low as 10 microseconds (or higher) can have a negative impact on the console input (some key presses do not register) while 0 makes the console fully responsive. The test consist in running "spawn sleep 10" and typing a command. I suspect other platforms may behave similarly, therefore do not bother with the added complexity of a configurable delay. - Apply review tags Changes in v3: - Rebase on top of Heinrich's series "common: cleanup usage of structure jmp_buf_data": https://patchwork.ozlabs.org/project/uboot/list/?series=446674 https://lists.denx.de/pipermail/u-boot/2025-March/582221.html - HAVE_INITJMP now depends on HAVE_SETJMP. Provide proper Sphinx-like documentaion for initjmp(). - test/lib/initjmp.c: change SPDX license tag from GPL2.0+ to GPL-2.0-or-later - Add doc/api/setjmp.rst. The initjmp() test is used as an example in the documentation. - uthread_create() now accepts an optional user-allocated struct uthread - Remove the list_empty() test from uthread_schedule() (not needed) - Add Sphinx doc to all functions in uthread.h (moved from uthread.c). - Add doc/api/uthread.rst. The uthread test is used as an example in the documentation. - Document struct uthread and its components - Provide numbers to justify the scheduling loop in udelay() in commit "lib: time: hook uthread_schedule() into udelay()". - Do not insert uthread_schedule() in common/console.c:fgetc() since it is already in schedule() - The wait command can be interrupted with Ctrl-C - Switch spawn and wait tests from DM_TEST() to CMD_TEST() - Add MAINTAINERS entry - Apply review tags Changes in v2: - Rewrite the cover letter, do not mention the older coroutines series - Rebased onto next - UTHREAD_STACK_SIZE is set to 32768 (32 KiB) instead of 32178 - Remove uthread_free_all() and let threads be freed as they terminate by uthread_schedule() - Add function descriptions - Add documentation (doc/develop/uthread.rst) - Explain initjmp() in the description of "arch: introduce symbol HAVE_INITJMP". - Add thread groups (uthread_grp_new_id() and uthread_grp_done()) - Add the spawn and wait commands Jerome Forissier (14): arch: introduce initjmp() and Kconfig symbol HAVE_INITJMP arm: add initjmp() riscv: add initjmp() sandbox: add initjmp() test: lib: add initjmp() test uthread: add cooperative multi-tasking interface cyclic: invoke uthread_schedule() from schedule() lib: time: hook uthread_schedule() into udelay() test: lib: add uthread test dm: usb: move bus initialization into new static function usb_init_bus() dm: usb: initialize and scan multiple buses simultaneously with uthread cmd: add spawn and wait commands test: cmd: add test for spawn and wait commands MAINTAINERS: add UTHREAD MAINTAINERS | 9 ++ arch/Kconfig | 9 ++ arch/arm/lib/setjmp.S | 12 +++ arch/arm/lib/setjmp_aarch64.S | 10 ++ arch/riscv/lib/setjmp.S | 11 ++ arch/sandbox/cpu/Makefile | 11 +- arch/sandbox/cpu/initjmp.c | 175 +++++++++++++++++++++++++++++++ cmd/Kconfig | 17 +++ cmd/Makefile | 2 + cmd/spawn.c | 188 ++++++++++++++++++++++++++++++++++ common/cyclic.c | 3 + doc/api/index.rst | 2 + doc/api/setjmp.rst | 20 ++++ doc/api/uthread.rst | 19 ++++ drivers/usb/host/usb-uclass.c | 168 +++++++++++++++++++++--------- include/setjmp.h | 32 ++++++ include/u-boot/schedule.h | 3 + include/uthread.h | 123 ++++++++++++++++++++++ lib/Kconfig | 21 ++++ lib/Makefile | 2 + lib/time.c | 9 +- lib/uthread.c | 139 +++++++++++++++++++++++++ test/boot/bootdev.c | 14 +-- test/boot/bootflow.c | 2 +- test/cmd/Makefile | 1 + test/cmd/spawn.c | 32 ++++++ test/lib/Makefile | 2 + test/lib/initjmp.c | 73 +++++++++++++ test/lib/uthread.c | 80 +++++++++++++++ 29 files changed, 1128 insertions(+), 61 deletions(-) create mode 100644 arch/sandbox/cpu/initjmp.c create mode 100644 cmd/spawn.c create mode 100644 doc/api/setjmp.rst create mode 100644 doc/api/uthread.rst create mode 100644 include/uthread.h create mode 100644 lib/uthread.c create mode 100644 test/cmd/spawn.c create mode 100644 test/lib/initjmp.c create mode 100644 test/lib/uthread.c -- 2.43.0
