From: Joseph Salisbury Date: Fri, 3 Apr 2026 21:00:14 +0000 (-0400) Subject: sched: Use u64 for bandwidth ratio calculations X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c6e80201e057dfb7253385e60bf541121bf5dc33;p=thirdparty%2Fkernel%2Flinux.git sched: Use u64 for bandwidth ratio calculations to_ratio() computes BW_SHIFT-scaled bandwidth ratios from u64 period and runtime values, but it returns unsigned long. tg_rt_schedulable() also stores the current group limit and the accumulated child sum in unsigned long. On 32-bit builds, large bandwidth ratios can be truncated and the RT group sum can wrap when enough siblings are present. That can let an overcommitted RT hierarchy pass the schedulability check, and it also narrows the helper result for other callers. Return u64 from to_ratio() and use u64 for the RT group totals so bandwidth ratios are preserved and compared at full width on both 32-bit and 64-bit builds. Fixes: b40b2e8eb521 ("sched: rt: multi level group constraints") Assisted-by: Codex:GPT-5 Signed-off-by: Joseph Salisbury Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260403210014.2713404-1-joseph.salisbury@oracle.com --- diff --git a/kernel/sched/core.c b/kernel/sched/core.c index c15c9865299e7..49cd5d2171613 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4735,7 +4735,7 @@ void sched_post_fork(struct task_struct *p) scx_post_fork(p); } -unsigned long to_ratio(u64 period, u64 runtime) +u64 to_ratio(u64 period, u64 runtime) { if (runtime == RUNTIME_INF) return BW_UNIT; diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 4e5f1957b91b1..a48e867949136 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2666,7 +2666,7 @@ static int tg_rt_schedulable(struct task_group *tg, void *data) { struct rt_schedulable_data *d = data; struct task_group *child; - unsigned long total, sum = 0; + u64 total, sum = 0; u64 period, runtime; period = ktime_to_ns(tg->rt_bandwidth.rt_period); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 9594355a36811..c95584191d58f 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2907,7 +2907,7 @@ extern void init_cfs_throttle_work(struct task_struct *p); #define MAX_BW_BITS (64 - BW_SHIFT) #define MAX_BW ((1ULL << MAX_BW_BITS) - 1) -extern unsigned long to_ratio(u64 period, u64 runtime); +extern u64 to_ratio(u64 period, u64 runtime); extern void init_entity_runnable_average(struct sched_entity *se); extern void post_init_entity_util_avg(struct task_struct *p);