mainlining shenanigans
777570d9ef
The synchronous RCU-tasks grace-period-wait primitives invoke schedule_timeout_idle() to give readers a chance to exit their read-side critical sections. Unfortunately, this fails during early boot on PREEMPT_RT because PREEMPT_RT relies solely on ksoftirqd to run timer handlers. Because ksoftirqd cannot operate until its kthreads are spawned, there is a brief period of time following scheduler initialization where PREEMPT_RT cannot run the timer handlers that schedule_timeout_idle() relies on, resulting in a hang. To avoid this boot-time hang, this commit replaces schedule_timeout_idle() with schedule_hrtimeout(), so that the timer expires in hardirq context. This is ensures that the timer fires even on PREEMPT_RT throughout the irqs-enabled portions of boot as well as during runtime. The timer is set to expire between fract and fract + HZ / 2 jiffies in order to align with any other timers that might expire during that time, thus reducing the number of wakeups. Note that RCU-tasks grace periods are infrequent, so the use of hrtimer should be fine. In contrast, in common-case code, user of hrtimer could result in performance issues. Cc: Martin KaFai Lau <kafai@fb.com> Cc: Andrii Nakryiko <andrii@kernel.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> |
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| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.