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| author | Hungyu Lin <dennylin0707@gmail.com> | 2026-10-20 21:01:57 +0000 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-10-24 00:46:49 -0700 |
| commit | 6b30c39a5e333cfb1475acf0f73de6ef954eea8a (patch) | |
| tree | d9345dd0d9b8a790d6ab36be4788e6b7dad0121a /scripts/Makefile.thinlto | |
| parent | 26d7e34b4226709084461a07bf28d9066fa96d8c (diff) | |
| download | linux-next-6b30c39a5e333cfb1475acf0f73de6ef954eea8a.tar.gz linux-next-6b30c39a5e333cfb1475acf0f73de6ef954eea8a.zip | |
compat: avoid double rounding in times()
do_sys_times() already converts CPU time to USER_HZ ticks. The compat
path converts each value back to jiffies before converting it to
COMPAT_USER_HZ. This round trip can lose precision even when the two
userspace rates match.
With HZ=250 and USER_HZ=COMPAT_USER_HZ=100, one user tick becomes two
jiffies and then zero compat ticks. Every odd tick count loses one tick,
so any of the four tms fields can underreport CPU time by an additional 10
ms.
Return the value directly when the native and compat units match. Keep
the existing conversion for differing rates.
Link: https://lore.kernel.org/20261020210157.52057-1-dennylin0707@gmail.com
Fixes: f06febc96ba8 ("timers: fix itimer/many thread hang")
Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: <stable@vger.kernel.org>
Diffstat (limited to 'scripts/Makefile.thinlto')
0 files changed, 0 insertions, 0 deletions