- When stime is larger than rtime due to accounting imprecision, then
utime = rtime - stime becomes negative. As this is unsigned math, the
result becomes a huge positive number. Cure it by resetting stime to
rtime in that case, so utime becomes 0.
- Restore consistent state when sched_cpu_deactivate() fails.
When offlining a CPU fails in sched_cpu_deactivate() after the SMT
present counter has been decremented, then the function aborts but
fails to increment the SMT present counter and leaves it imbalanced.
Consecutive operations cause it to underflow. Add the missing fixup
for the error path.
As SMT accounting the runqueue needs to marked online again in the
error exit path to restore consistent state.
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Merge tag 'sched-urgent-2024-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Thomas Gleixner:
- When stime is larger than rtime due to accounting imprecision, then
utime = rtime - stime becomes negative. As this is unsigned math, the
result becomes a huge positive number.
Cure it by resetting stime to rtime in that case, so utime becomes 0.
- Restore consistent state when sched_cpu_deactivate() fails.
When offlining a CPU fails in sched_cpu_deactivate() after the SMT
present counter has been decremented, then the function aborts but
fails to increment the SMT present counter and leaves it imbalanced.
Consecutive operations cause it to underflow. Add the missing fixup
for the error path.
For SMT accounting the runqueue needs to marked online again in the
error exit path to restore consistent state.
* tag 'sched-urgent-2024-08-04' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/core: Fix unbalance set_rq_online/offline() in sched_cpu_deactivate()
sched/core: Introduce sched_set_rq_on/offline() helper
sched/smt: Fix unbalance sched_smt_present dec/inc
sched/smt: Introduce sched_smt_present_inc/dec() helper
sched/cputime: Fix mul_u64_u64_div_u64() precision for cputime
6cc82dc2bd