On Tue, Sep 16 2025 at 03:19, Wake Liu wrote:
The timespec_sub function, as implemented in several timer
timespec_sub()
https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#function-...
selftests, is prone to integer overflow on 32-bit systems.
The calculation `NSEC_PER_SEC * b.tv_sec` is performed using 32-bit arithmetic, and the result overflows before being stored in the 64-bit `ret` variable. This leads to incorrect time delta calculations and test failures.
As suggested by tglx, this patch fixes the issue by:
s/this patch fixes/fix/
Creating a new `static inline` helper function, `timespec_to_ns`, which safely converts a `timespec` to nanoseconds by casting `tv_sec` to `long long` before multiplying with `NSEC_PER_SEC`.
Placing the new helper and a rewritten `timespec_sub` into a common header: tools/testing/selftests/timers/helpers.h.
Removing the duplicated, buggy implementations from all timer selftests and replacing them with an #include of the new header.
This consolidates the code and ensures the calculation is correctly performed using 64-bit arithmetic across all tests.
This lacks a Signed-off-by.
Changes in v2:
- Per tglx's feedback, instead of changing NSEC_PER_SEC globally, this version consolidates the buggy timespec_sub() implementations into a new 32-bit safe inline function in a shared header.
- Amended the commit message to be more descriptive.
change logs go behind the '---' separator as they are not part of the commit message. It's documented how to format a change log properly.
-#define UNREASONABLE_LAT (NSEC_PER_SEC * 5) /* hopefully we resume in 5 secs */ +#define UNREASONABLE_LAT (NSEC_PER_SEC * 5LL) /* hopefully we resume in 5 secs */
How is this change and the pile of similar ones related to $subject and why are they required in the first place?
index 000000000000..652f20247091 --- /dev/null +++ b/tools/testing/selftests/timers/helpers.h @@ -0,0 +1,31 @@
Lacks a SPDX identifier.
scripts/checkpatch.pl exists for a reason.
Thanks,
tglx