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-references-in-changelogs > 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/ > 1. 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`. > > 2. Placing the new helper and a rewritten `timespec_sub` into > a common header: tools/testing/selftests/timers/helpers.h. > > 3. 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
