| commit | 3d8ee5c555e4930f876b8629ea82112672a28883 | [log] [tgz] |
|---|---|---|
| author | Nick Maniscalco <maniscalco@google.com> | Fri Sep 14 11:09:07 2018 -0700 |
| committer | CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org> | Thu Sep 20 15:11:56 2018 +0000 |
| tree | f5906be97197a7a625c35509a002ffe317d027ad | |
| parent | 0bfcef81e3fed72809411f084a088618bf322d78 [diff] |
[kernel][arm64][mp][timer] Make arch_spinloop_pause a no-op on arm64 This change removes arch_spinloop_signal and changes arm64's arch_spinloop_pause to issue YIELD rather than WFE. The purpose of this change is to eliminate potential bugs that may arise from WFE with no corresponding SEV. In two places (timer.cpp and mp.cpp) arch_spinloop_pause, in conjunction with arch_spinloop_signal, is used to create a kind of condition variable, suspending execution until another CPU calls arch_spinloop_signal. Elsewhere (like some UART drivers), it is simply used as a hinting no-op in busy loops. On x64, arch_spinloop_pause is PAUSE and arch_spinloop_signal is empty. On arm64, arch_spinloop_pause is WFE (Wait For Event) and arch_spinloop_signal is SEV (Send Event). WFE suspends execution until an event is signaled (via SEV, global monitor transition, etc.). This means that any use of WFE without a corresponding SEV (or other mechanism like Load-Exclusive) could potentially suspend the CPU for an indefinite period of time. Test: On VIM2 and Eve, ran the following: - k ut sync_ipi_tests - k ut timer - k timer_stress 60 ZX-2562 #comment followup Change-Id: If2b8facef4845865d5bfe7a4d0089cd5aef791a6
Zircon is the core platform that powers the Fuchsia OS. Zircon is composed of a microkernel (source in kernel/...) as well as a small set of userspace services, drivers, and libraries (source in system/...) necessary for the system to boot, talk to hardware, load userspace processes and run them, etc. Fuchsia builds a much larger OS on top of this foundation.
The canonical Zircon Git repository is located at: https://fuchsia.googlesource.com/zircon
A read-only mirror of the code is present at: https://github.com/fuchsia-mirror/zircon
The Zircon Kernel provides syscalls to manage processes, threads, virtual memory, inter-process communication, waiting on object state changes, and locking (via futexes).
Currently there are some temporary syscalls that have been used for early bringup work, which will be going away in the future as the long term syscall API/ABI surface is finalized. The expectation is that there will be about 100 syscalls.
Zircon syscalls are generally non-blocking. The wait_one, wait_many port_wait and thread sleep being the notable exceptions.
This page is a non-comprehensive index of the zircon documentation.