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kernel: fix timeout bugs

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When CONFIG_TIMEOUT_64BIT is y, positive values are relative/delta
timeouts and negative values are absolute timeouts, except
for two special values. -1 is K_WAIT_FOREVER and 0 is K_NO_WAIT.
The reserved value of -1 means INT64_MAX is not a valid argument
to K_TIMEOUT_ABS_TICKS(), but there was no check. If a literal
was passed, a preprocessor/compiler warning would be generated
for overflow, but if a variable was passed as the argument,
then the code would compile but not work correctly since the
absolute timeout would be changed to a relative one. One
example of this is task_wdt_init() if no channels are enabled.

Rather than just fixing task_wdt, and trying to find other cases
in an adhoc way, this CL changes K_TIMEOUT_ABS_TICKS() to
limit the larges value to (INT64_MAX-1). It does so silently,
but given the range of int64_t, there should be no practical
difference.

Also, change the implementation for Z_IS_TIMEOUT_RELATIVE() to
fix the case where INT64_MAX relative timeout was being
improperly reported as being not a relative timeout. This was
again due to the -1 reserved value.

Add some tests for these changes to the timer_api test.

Signed-off-by: Mike J. Chen <mjchen@google.com>
This commit is contained in:
Mike J. Chen 2025-03-13 15:40:53 -07:00 • committed by Benjamin Cabé
commit 9075d53355
3 changed files with 64 additions and 3 deletions
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4
include/zephyr/kernel.h
View file

@ -1488,13 +1488,13 @@ const char *k_thread_state_str(k_tid_t thread_id, char *buf, size_t buf_size);
* This macro generates a timeout delay that represents an expiration
* at the absolute uptime value specified, in system ticks. That is, the
* timeout will expire immediately after the system uptime reaches the
* specified tick count.
* specified tick count. Value is clamped to the range 0 to INT64_MAX-1.
*
* @param t Tick uptime value
* @return Timeout delay value
*/
#define K_TIMEOUT_ABS_TICKS(t) \
Z_TIMEOUT_TICKS(Z_TICK_ABS((k_ticks_t)MAX(t, 0)))
Z_TIMEOUT_TICKS(Z_TICK_ABS((k_ticks_t)CLAMP(t, 0, (INT64_MAX - 1))))
/**
* @brief Generates an absolute/uptime timeout value from seconds

9
include/zephyr/sys_clock.h
View file

@ -151,7 +151,14 @@ typedef struct {
/* Test for relative timeout */
#if CONFIG_TIMEOUT_64BIT
#define Z_IS_TIMEOUT_RELATIVE(timeout) (Z_TICK_ABS((timeout).ticks) < 0)
/* Positive values are relative/delta timeouts and negative values are absolute
* timeouts, except -1 which is reserved for K_TIMEOUT_FOREVER. 0 is K_NO_WAIT,
* which is historically considered a relative timeout.
* K_TIMEOUT_FOREVER is not considered a relative timeout and neither is it
* considerd an absolute timeouts (so !Z_IS_TIMEOUT_RELATIVE() does not
* necessarily mean it is an absolute timeout if ticks == -1);
*/
#define Z_IS_TIMEOUT_RELATIVE(timeout) (((timeout).ticks) >= 0)
#else
#define Z_IS_TIMEOUT_RELATIVE(timeout) true
#endif

54
tests/kernel/timer/timer_api/src/main.c
View file

@ -752,6 +752,33 @@ ZTEST_USER(timer_api, test_timeout_abs)
/* Ensure second alignment for K_TIMEOUT_ABS_SEC */
zassert_true(exp_ms % MSEC_PER_SEC == 0);
/* Check K_TIMEOUT_ABS_TICKS() and Z_IS_TIMEOUT_RELATIVE macros */
t2 = K_NO_WAIT;
zassert_true(Z_IS_TIMEOUT_RELATIVE(t2));
t2 = K_TICKS(1);
zassert_true(Z_IS_TIMEOUT_RELATIVE(t2));
t2 = K_TICKS(INT64_MAX-1);
zassert_true(Z_IS_TIMEOUT_RELATIVE(t2));
t2 = K_TICKS(INT64_MAX);
zassert_true(Z_IS_TIMEOUT_RELATIVE(t2));
zassert_false(Z_IS_TIMEOUT_RELATIVE(t));
t2 = K_TIMEOUT_ABS_TICKS(1);
zassert_false(Z_IS_TIMEOUT_RELATIVE(t2));
t2 = K_TIMEOUT_ABS_TICKS(INT64_MAX-1);
zassert_false(Z_IS_TIMEOUT_RELATIVE(t2));
/* Check when INT64_MAX passed to K_TIMEOUT_ABS_TICKS(), with
* both a literal and variable argument.
*/
t2 = K_TIMEOUT_ABS_TICKS(INT64_MAX);
zassert_false(Z_IS_TIMEOUT_RELATIVE(t2));
uint64_t max_int64 = INT64_MAX;
t2 = K_TIMEOUT_ABS_TICKS(max_int64);
zassert_false(Z_IS_TIMEOUT_RELATIVE(t2));
/* Check the other generator macros to make sure they produce
* the same (whiteboxed) converted values
*/
@ -796,6 +823,33 @@ ZTEST_USER(timer_api, test_timeout_abs)
t0+rem_ticks-exp_ticks);
k_timer_stop(&remain_timer);
/* Rerun test with t set to INT64_MAX. K_TIMEOUT_ABS_TICKS()
* should adjust the abs timeout to INT64_MAX-1 because the negative
* range used for absolute timeouts needs to reserve -1 for
* K_TIMEOUT_FOREVER.
*/
init_timer_data();
exp_ticks = INT64_MAX - 1;
k_timer_start(&remain_timer, K_TIMEOUT_ABS_TICKS(INT64_MAX), K_FOREVER);
if (IS_ENABLED(CONFIG_MULTITHREADING)) {
k_usleep(1);
}
do {
t0 = k_uptime_ticks();
rem_ticks = k_timer_remaining_ticks(&remain_timer);
t1 = k_uptime_ticks();
} while (t0 != t1);
zassert_true(t0 + rem_ticks == exp_ticks,
"Wrong remaining: now %lld rem %lld expires %lld (%lld)",
(uint64_t)t0, (uint64_t)rem_ticks, (uint64_t)exp_ticks,
t0+rem_ticks-exp_ticks);
k_timer_stop(&remain_timer);
#endif
}