0f444c84e5
Qemu doesn't like tickless. By default[1] it tries to be realtime as vied by the host CPU -- presenting read values from hardware cycle counters and interrupt timings at the appropriate real world clock times according to whatever the simulated counter frequency is. But when the host system is loaded, there is always the problem that the qemu process might not see physical CPU time for large chunks of time (i.e. a host OS scheduling quantum -- generally about the same size as guest ticks!) leading to lost cycles. When those timer interrupts are delivered by the emulated hardware at fixed frequencies without software intervention, that's not so bad: the work the guest has to do after the interrupt generally happens synchronously (because the qemu process has just started running) and nothing notices the dropout. But with tickless, the interrupts need to be explicitly programmed by guest software! That means the driver needs to be sure it's going to get some real CPU time within some small fraction of a Zephyr tick of the right time, otherwise the computations get wonky. The end result is that qemu tends to work with tickless well on an unloaded/idle run, but not in situations (like sanitycheck) where it needs to content with other processes for host CPU. So, add a flag that drivers can use to "fake" tickless behavior when run under qemu (only), and enable it (only!) for the small handful of tests that are having trouble. [1] There is an -icount feature to implement proper cycle counting at the expense of real-world-time correspondence. Maybe someday we might get it to work for us. Signed-off-by: Andy Ross <andrew.j.ross@intel.com> |
||
|---|---|---|
| .. | ||
| src | ||
| CMakeLists.txt | ||
| README.txt | ||
| prj.conf | ||
| testcase.yaml | ||
README.txt
Title: cooperative thread Sleep and Wakeup APIs
Description:
This test verifies that cooperative sleep and wakeup APIs operate as
expected.
---------------------------------------------------------------------------
Building and Running Project:
This project outputs to the console. It can be built and executed
on QEMU as follows:
make run
---------------------------------------------------------------------------
Troubleshooting:
Problems caused by out-dated project information can be addressed by
issuing one of the following commands then rebuilding the project:
make clean # discard results of previous builds
# but keep existing configuration info
or
make pristine # discard results of previous builds
# and restore pre-defined configuration info
---------------------------------------------------------------------------
Sample Output:
tc_start() - Test kernel Sleep and Wakeup APIs
Kernel objects initialized
Test thread started: id = 0x00103044
Helper thread started: id = 0x00102f44
Testing normal expiration of k_sleep()
Testing: test thread sleep + helper thread wakeup test
Testing: test thread sleep + isr offload wakeup test
Testing: test thread sleep + main wakeup test thread
Testing kernel k_sleep()
===================================================================
PROJECT EXECUTION SUCCESSFUL