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arch: riscv: disable interrupts before wfi

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According to RISC-V Instruction Set Manual Chapter 3.3.2:
"The operation of WFI must be unaffected by the global interrupt
bits in mstatus
[...]
WFI is also required to resume execution for locally enabled
interrupts pending at any privilege level,
regardless of the global interrupt enable at each privilege level."

Disabling interrupts before executing `wfi` prevents a corner case
where an IRQ is presented just before executing `wfi`,
which would cause it to return directly into `wfi` and potentially
get stuck in sleep, instead of continuing to background processing.

When execution is resumed, interrupts are reenabled
and appropriate IRQ Handlers should be executed.

Signed-off-by: Marcin Szymczyk <marcin.szymczyk@nordicsemi.no>
This commit is contained in:
Marcin Szymczyk 2024-03-14 16:57:42 +01:00 • committed by Carles Cufí
commit 292aafef5a
1 changed files with 2 additions and 2 deletions
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4
arch/riscv/core/cpu_idle.c
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@ -10,13 +10,13 @@
void __weak arch_cpu_idle(void)
{
sys_trace_idle();
irq_unlock(MSTATUS_IEN);
__asm__ volatile("wfi");
irq_unlock(MSTATUS_IEN);
}
void __weak arch_cpu_atomic_idle(unsigned int key)
{
sys_trace_idle();
irq_unlock(key);
__asm__ volatile("wfi");
irq_unlock(key);
}