[PATCH v5 00/16] Uthreads

[Tom Rini]

On Mon, Mar 31, 2025 at 02:30:54PM +0200, Jerome Forissier wrote:

> This series introduces threads and uses them for two things:
> - Improve the performance of the USB bus scanning code (scan multiple
> busses simultaneously),
> - 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.
> 
> The schedule() and udelay() function are updated to become thread
> re-scheduling points, and mutex objects are introduced. With that 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

So, we're nearly there. But there's some CI problems. First, CI isn't
testing this because nothing enables UTHREADS. I don't know if we should
enable it by default on qemu_arm64 for example or not. But for testing,
I added this to .gitlab-ci.yml (and something similar would work for
Azure):
qemu_arm64_uthread test.py:
  variables:
    TEST_PY_BD: "qemu_arm64"
    TEST_PY_TEST_SPEC: "not sleep"
    OVERRIDE: "-a CONFIG_UTHREAD=y -a CONFIG_CMD_SPAWN=y -a CONFIG_UNIT_TEST=y"
  <<: *buildman_and_testpy_dfn

This however leads first to unrelated tests failing:
https://source.denx.de/u-boot/u-boot/-/jobs/1099921

And I didn't see if the new tests ran either.

-- 
Tom
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