kernel.git/kernel/sched, branch linux-rolling-lts

sched_ext: Fix enqueue_task_scx() truncation of upper enqueue flags

2026-03-19T15:08:43Z

commit 57ccf5ccdc56954f2a91a7f66684fd31c566bde5 upstream. enqueue_task_scx() takes int enq_flags from the sched_class interface. SCX enqueue flags starting at bit 32 (SCX_ENQ_PREEMPT and above) are silently truncated when passed through activate_task(). extra_enq_flags was added as a workaround - storing high bits in rq->scx.extra_enq_flags and OR-ing them back in enqueue_task_scx(). However, the OR target is still the int parameter, so the high bits are lost anyway. The current impact is limited as the only affected flag is SCX_ENQ_PREEMPT which is informational to the BPF scheduler - its loss means the scheduler doesn't know about preemption but doesn't cause incorrect behavior. Fix by renaming the int parameter to core_enq_flags and introducing a u64 enq_flags local that merges both sources. All downstream functions already take u64 enq_flags. Fixes: f0e1a0643a59 ("sched_ext: Implement BPF extensible scheduler class") Cc: stable@vger.kernel.org # v6.12+ Acked-by: Andrea Righi Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

sched_ext: Remove redundant css_put() in scx_cgroup_init()

2026-03-19T15:08:22Z

commit 1336b579f6079fb8520be03624fcd9ba443c930b upstream. The iterator css_for_each_descendant_pre() walks the cgroup hierarchy under cgroup_lock(). It does not increment the reference counts on yielded css structs. According to the cgroup documentation, css_put() should only be used to release a reference obtained via css_get() or css_tryget_online(). Since the iterator does not use either of these to acquire a reference, calling css_put() in the error path of scx_cgroup_init() causes a refcount underflow. Remove the unbalanced css_put() to prevent a potential Use-After-Free (UAF) vulnerability. Fixes: 819513666966 ("sched_ext: Add cgroup support") Cc: stable@vger.kernel.org # v6.12+ Signed-off-by: Cheng-Yang Chou Reviewed-by: Andrea Righi Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

sched: idle: Make skipping governor callbacks more consistent

2026-03-19T15:08:19Z

[ Upstream commit d557640e4ce589a24dca5ca7ce3b9680f471325f ] If the cpuidle governor .select() callback is skipped because there is only one idle state in the cpuidle driver, the .reflect() callback should be skipped as well, at least for consistency (if not for correctness), so do it. Fixes: e5c9ffc6ae1b ("cpuidle: Skip governor when only one idle state is available") Signed-off-by: Rafael J. Wysocki Reviewed-by: Christian Loehle Reviewed-by: Aboorva Devarajan Reviewed-by: Frederic Weisbecker Link: https://patch.msgid.link/12857700.O9o76ZdvQC@rafael.j.wysocki Signed-off-by: Sasha Levin

sched_ext: Fix SCX_EFLAG_INITIALIZED being a no-op flag

2026-03-12T11:09:22Z

[ Upstream commit 749989b2d90ddc7dd253ad3b11a77cf882721acf ] SCX_EFLAG_INITIALIZED is the sole member of enum scx_exit_flags with no explicit value, so the compiler assigns it 0. This makes the bitwise OR in scx_ops_init() a no-op: sch->exit_info->flags |= SCX_EFLAG_INITIALIZED; /* |= 0 */ As a result, BPF schedulers cannot distinguish whether ops.init() completed successfully by inspecting exit_info->flags. Assign the value 1LLU << 0 so the flag is actually set. Fixes: f3aec2adce8d ("sched_ext: Add SCX_EFLAG_INITIALIZED to indicate successful ops.init()") Signed-off-by: David Carlier Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin

sched/fair: Fix lag clamp

2026-03-12T11:09:13Z

[ Upstream commit 6e3c0a4e1ad1e0455b7880fad02b3ee179f56c09 ] Vincent reported that he was seeing undue lag clamping in a mixed slice workload. Implement the max_slice tracking as per the todo comment. Fixes: 147f3efaa241 ("sched/fair: Implement an EEVDF-like scheduling policy") Reported-off-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Tested-by: Vincent Guittot Tested-by: K Prateek Nayak Tested-by: Shubhang Kaushik Link: https://patch.msgid.link/20250422101628.GA33555@noisy.programming.kicks-ass.net Signed-off-by: Sasha Levin

sched/eevdf: Update se->vprot in reweight_entity()

2026-03-12T11:09:13Z

[ Upstream commit ff38424030f98976150e42ca35f4b00e6ab8fa23 ] In the EEVDF framework with Run-to-Parity protection, `se->vprot` is an independent variable defining the virtual protection timestamp. When `reweight_entity()` is called (e.g., via nice/renice), it performs the following actions to preserve Lag consistency: 1. Scales `se->vlag` based on the new weight. 2. Calls `place_entity()`, which recalculates `se->vruntime` based on the new weight and scaled lag. However, the current implementation fails to update `se->vprot`, leading to mismatches between the task's actual runtime and its expected duration. Fixes: 63304558ba5d ("sched/eevdf: Curb wakeup-preemption") Suggested-by: Zhang Qiao Signed-off-by: Wang Tao Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Tested-by: K Prateek Nayak Tested-by: Shubhang Kaushik Link: https://patch.msgid.link/20260120123113.3518950-1-wangtao554@huawei.com Signed-off-by: Sasha Levin

sched/fair: Only set slice protection at pick time

2026-03-12T11:09:12Z

[ Upstream commit bcd74b2ffdd0a2233adbf26b65c62fc69a809c8e ] We should not (re)set slice protection in the sched_change pattern which calls put_prev_task() / set_next_task(). Fixes: 63304558ba5d ("sched/eevdf: Curb wakeup-preemption") Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Vincent Guittot Tested-by: K Prateek Nayak Tested-by: Shubhang Kaushik Link: https://patch.msgid.link/20260219080624.561421378%40infradead.org Signed-off-by: Sasha Levin

sched/fair: Fix zero_vruntime tracking

2026-03-12T11:09:12Z

[ Upstream commit b3d99f43c72b56cf7a104a364e7fb34b0702828b ] It turns out that zero_vruntime tracking is broken when there is but a single task running. Current update paths are through __{en,de}queue_entity(), and when there is but a single task, pick_next_task() will always return that one task, and put_prev_set_next_task() will end up in neither function. This can cause entity_key() to grow indefinitely large and cause overflows, leading to much pain and suffering. Furtermore, doing update_zero_vruntime() from __{de,en}queue_entity(), which are called from {set_next,put_prev}_entity() has problems because: - set_next_entity() calls __dequeue_entity() before it does cfs_rq->curr = se. This means the avg_vruntime() will see the removal but not current, missing the entity for accounting. - put_prev_entity() calls __enqueue_entity() before it does cfs_rq->curr = NULL. This means the avg_vruntime() will see the addition *and* current, leading to double accounting. Both cases are incorrect/inconsistent. Noting that avg_vruntime is already called on each {en,de}queue, remove the explicit avg_vruntime() calls (which removes an extra 64bit division for each {en,de}queue) and have avg_vruntime() update zero_vruntime itself. Additionally, have the tick call avg_vruntime() -- discarding the result, but for the side-effect of updating zero_vruntime. While there, optimize avg_vruntime() by noting that the average of one value is rather trivial to compute. Test case: # taskset -c -p 1 $$ # taskset -c 2 bash -c 'while :; do :; done&' # cat /sys/kernel/debug/sched/debug | awk '/^cpu#/ {P=0} /^cpu#2,/ {P=1} {if (P) print $0}' | grep -e zero_vruntime -e "^>" PRE: .zero_vruntime : 31316.407903 >R bash 487 50787.345112 E 50789.145972 2.800000 50780.298364 16 120 0.000000 0.000000 0.000000 / .zero_vruntime : 382548.253179 >R bash 487 427275.204288 E 427276.003584 2.800000 427268.157540 23 120 0.000000 0.000000 0.000000 / POST: .zero_vruntime : 17259.709467 >R bash 526 17259.709467 E 17262.509467 2.800000 16915.031624 9 120 0.000000 0.000000 0.000000 / .zero_vruntime : 18702.723356 >R bash 526 18702.723356 E 18705.523356 2.800000 18358.045513 9 120 0.000000 0.000000 0.000000 / Fixes: 79f3f9bedd14 ("sched/eevdf: Fix min_vruntime vs avg_vruntime") Reported-by: K Prateek Nayak Signed-off-by: Peter Zijlstra (Intel) Tested-by: K Prateek Nayak Tested-by: Shubhang Kaushik Link: https://patch.msgid.link/20260219080624.438854780%40infradead.org Signed-off-by: Sasha Levin

sched/fair: Introduce and use the vruntime_cmp() and vruntime_op() wrappers for wrapped-signed aritmetics

2026-03-12T11:09:12Z

[ Upstream commit 5758e48eefaf111d7764d8f1c8b666140fe5fa27 ] We have to be careful with vruntime comparisons and subtraction, due to the possibility of wrapping, so we have macros like: #define vruntime_gt(field, lse, rse) ({ (s64)((lse)->field - (rse)->field) > 0; }) Which is used like this: if (vruntime_gt(min_vruntime, se, rse)) se->min_vruntime = rse->min_vruntime; Replace this with an easier to read pattern that uses the regular arithmetics operators: if (vruntime_cmp(se->min_vruntime, ">", rse->min_vruntime)) se->min_vruntime = rse->min_vruntime; Also replace vruntime subtractions with vruntime_op(): - delta = (s64)(sea->vruntime - seb->vruntime) + - (s64)(cfs_rqb->zero_vruntime_fi - cfs_rqa->zero_vruntime_fi); + delta = vruntime_op(sea->vruntime, "-", seb->vruntime) + + vruntime_op(cfs_rqb->zero_vruntime_fi, "-", cfs_rqa->zero_vruntime_fi); In the vruntime_cmp() and vruntime_op() macros use Use __builtin_strcmp(), because of __HAVE_ARCH_STRCMP might turn off the compiler optimizations we rely on here to catch usage bugs. No change in functionality. Signed-off-by: Ingo Molnar Stable-dep-of: b3d99f43c72b ("sched/fair: Fix zero_vruntime tracking") Signed-off-by: Sasha Levin

sched/fair: Rename cfs_rq::avg_vruntime to ::sum_w_vruntime, and helper functions

2026-03-12T11:09:12Z

[ Upstream commit dcbc9d3f0e594223275a18f7016001889ad35eff ] The ::avg_vruntime field is a misnomer: it says it's an 'average vruntime', but in reality it's the momentary sum of the weighted vruntimes of all queued tasks, which is at least a division away from being an average. This is clear from comments about the math of fair scheduling: * \Sum (v_i - v0) * w_i := cfs_rq->avg_vruntime This confusion is increased by the cfs_avg_vruntime() function, which does perform the division and returns a true average. The sum of all weighted vruntimes should be named thusly, so rename the field to ::sum_w_vruntime. (As arguably ::sum_weighted_vruntime would be a bit of a mouthful.) Understanding the scheduler is hard enough already, without extra layers of obfuscated naming. ;-) Also rename related helper functions: sum_vruntime_add() => sum_w_vruntime_add() sum_vruntime_sub() => sum_w_vruntime_sub() sum_vruntime_update() => sum_w_vruntime_update() With the notable exception of cfs_avg_vruntime(), which was named accurately. Signed-off-by: Ingo Molnar Link: https://patch.msgid.link/20251201064647.1851919-7-mingo@kernel.org Stable-dep-of: b3d99f43c72b ("sched/fair: Fix zero_vruntime tracking") Signed-off-by: Sasha Levin