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kernel/sched: correct k_sleep() return value calculation

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Fix the issue: https://github.com/zephyrproject-rtos/zephyr/issues/79863

The expected_wakeup_ticks and sys_clock_tick_get_32() are uint32_t values,
and may wrap around individually.
If the expected_wakeup_ticks has a wraparound and sys_clock_tick_get_32()
doesn't, so expected_wakeup_ticks < sys_clock_tick_get_32(), the API return
value will be corrupted.

The API return value, that is the remaining time, should be calculated in
32bit-unsigned-integer manner, and any wraparound will be treated properly.

Signed-off-by: Akaiwa Wataru <akaiwa@sonas.co.jp>
This commit is contained in:
Akaiwa Wataru 2024-11-28 23:23:37 +09:00 • committed by Benjamin Cabé
commit feefb7dd35
1 changed files with 5 additions and 1 deletions
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6
kernel/sched.c
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@ -1117,7 +1117,11 @@ static int32_t z_tick_sleep(k_ticks_t ticks)
__ASSERT(!z_is_thread_state_set(arch_current_thread(), _THREAD_SUSPENDED), "");
ticks = (k_ticks_t)expected_wakeup_ticks - sys_clock_tick_get_32();
/* We require a 32 bit unsigned subtraction to care a wraparound */
uint32_t left_ticks = expected_wakeup_ticks - sys_clock_tick_get_32();
/* To handle a negative value correctly, once type-cast it to signed 32 bit */
ticks = (k_ticks_t)(int32_t)left_ticks;
if (ticks > 0) {
return ticks;
}