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kernel/idle: Fix !SCHED_IPI_SUPPORTED

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The requirement for k_yield() to handle "yielding" in the idle thread
was removed a while back, but it missed a spot where we'd try to yield
in the fallback loop on bringup platforms that lack an IPI.  This now
crashes, because yield now unconditionally tries to reschedule the
current thread, which doesn't work for idle threads that don't live in
the run queue.

Just make it a busy loop calling swap(), even simpler.

Fixes #50119

Signed-off-by: Andy Ross <andyross@google.com>
This commit is contained in:
Andy Ross 2022-09-13 10:13:40 -07:00 committed by Carles Cufí
parent d9206aa29b
commit 0ca7150f90
1 changed files with 10 additions and 10 deletions
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20
kernel/idle.c
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@ -39,19 +39,19 @@ void idle(void *unused1, void *unused2, void *unused3)
__ASSERT_NO_MSG(_current->base.prio >= 0);
while (true) {
/* SMP systems without a working IPI can't
* actual enter an idle state, because they
* can't be notified of scheduler changes
* (i.e. threads they should run). They just
* spin in a yield loop. This is intended as
* a fallback configuration for new platform
* bringup.
/* SMP systems without a working IPI can't actual
* enter an idle state, because they can't be notified
* of scheduler changes (i.e. threads they should
* run). They just spin instead, with a minimal
* relaxation loop to prevent hammering the scheduler
* lock and/or timer driver. This is intended as a
* fallback configuration for new platform bringup.
*/
if (IS_ENABLED(CONFIG_SMP) &&
!IS_ENABLED(CONFIG_SCHED_IPI_SUPPORTED)) {
k_busy_wait(100);
k_yield();
continue;
for (volatile int i = 0; i < 100000; i++)
;
z_swap_unlocked();
}
/* Note weird API: k_cpu_idle() is called with local