linux/kernel/sched/ext.c, branch v6.16

sched/ext: Prevent update_locked_rq() calls with NULL rq

2025-07-17T01:02:12Z

Avoid invoking update_locked_rq() when the runqueue (rq) pointer is NULL in the SCX_CALL_OP and SCX_CALL_OP_RET macros. Previously, calling update_locked_rq(NULL) with preemption enabled could trigger the following warning: BUG: using __this_cpu_write() in preemptible [00000000] This happens because __this_cpu_write() is unsafe to use in preemptible context. rq is NULL when an ops invoked from an unlocked context. In such cases, we don't need to store any rq, since the value should already be NULL (unlocked). Ensure that update_locked_rq() is only called when rq is non-NULL, preventing calling __this_cpu_write() on preemptible context. Suggested-by: Peter Zijlstra Fixes: 18853ba782bef ("sched_ext: Track currently locked rq") Signed-off-by: Breno Leitao Acked-by: Andrea Righi Signed-off-by: Tejun Heo Cc: stable@vger.kernel.org # v6.15

sched_ext, sched/core: Don't call scx_group_set_weight() prematurely from sched_create_group()

2025-06-17T18:19:55Z

During task_group creation, sched_create_group() calls scx_group_set_weight() with CGROUP_WEIGHT_DFL to initialize the sched_ext portion. This is premature and ends up calling ops.cgroup_set_weight() with an incorrect @cgrp before ops.cgroup_init() is called. sched_create_group() should just initialize SCX related fields in the new task_group. Fix it by factoring out scx_tg_init() from sched_init() and making sched_create_group() call that function instead of scx_group_set_weight(). v2: Retain CONFIG_EXT_GROUP_SCHED ifdef in sched_init() as removing it leads to build failures on !CONFIG_GROUP_SCHED configs. Signed-off-by: Tejun Heo Fixes: 819513666966 ("sched_ext: Add cgroup support") Cc: stable@vger.kernel.org # v6.12+

sched_ext: Make scx_group_set_weight() always update tg->scx.weight

2025-06-17T18:19:43Z

Otherwise, tg->scx.weight can go out of sync while scx_cgroup is not enabled and ops.cgroup_init() may be called with a stale weight value. Signed-off-by: Tejun Heo Fixes: 819513666966 ("sched_ext: Add cgroup support") Cc: stable@vger.kernel.org # v6.12+

Merge tag 'bpf-next-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

2025-05-28T22:52:42Z

Pull bpf updates from Alexei Starovoitov: - Fix and improve BTF deduplication of identical BTF types (Alan Maguire and Andrii Nakryiko) - Support up to 12 arguments in BPF trampoline on arm64 (Xu Kuohai and Alexis Lothoré) - Support load-acquire and store-release instructions in BPF JIT on riscv64 (Andrea Parri) - Fix uninitialized values in BPF_{CORE,PROBE}_READ macros (Anton Protopopov) - Streamline allowed helpers across program types (Feng Yang) - Support atomic update for hashtab of BPF maps (Hou Tao) - Implement json output for BPF helpers (Ihor Solodrai) - Several s390 JIT fixes (Ilya Leoshkevich) - Various sockmap fixes (Jiayuan Chen) - Support mmap of vmlinux BTF data (Lorenz Bauer) - Support BPF rbtree traversal and list peeking (Martin KaFai Lau) - Tests for sockmap/sockhash redirection (Michal Luczaj) - Introduce kfuncs for memory reads into dynptrs (Mykyta Yatsenko) - Add support for dma-buf iterators in BPF (T.J. Mercier) - The verifier support for __bpf_trap() (Yonghong Song) * tag 'bpf-next-6.16' of git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (135 commits) bpf, arm64: Remove unused-but-set function and variable. selftests/bpf: Add tests with stack ptr register in conditional jmp bpf: Do not include stack ptr register in precision backtracking bookkeeping selftests/bpf: enable many-args tests for arm64 bpf, arm64: Support up to 12 function arguments bpf: Check rcu_read_lock_trace_held() in bpf_map_lookup_percpu_elem() bpf: Avoid __bpf_prog_ret0_warn when jit fails bpftool: Add support for custom BTF path in prog load/loadall selftests/bpf: Add unit tests with __bpf_trap() kfunc bpf: Warn with __bpf_trap() kfunc maybe due to uninitialized variable bpf: Remove special_kfunc_set from verifier selftests/bpf: Add test for open coded dmabuf_iter selftests/bpf: Add test for dmabuf_iter bpf: Add open coded dmabuf iterator bpf: Add dmabuf iterator dma-buf: Rename debugfs symbols bpf: Fix error return value in bpf_copy_from_user_dynptr libbpf: Use mmap to parse vmlinux BTF from sysfs selftests: bpf: Add a test for mmapable vmlinux BTF btf: Allow mmap of vmlinux btf ...

sched_ext: Make scx_kf_allowed_if_unlocked() available outside ext.c

2025-05-20T20:23:50Z

Relocate the scx_kf_allowed_if_unlocked(), so it can be used from other source files (e.g., ext_idle.c). No functional change. Signed-off-by: Andrea Righi Signed-off-by: Tejun Heo

sched_ext: Explain the temporary situation around scx_root dereferences

2025-05-14T16:37:18Z

Naked scx_root dereferences are being used as temporary markers to indicate that they need to be updated to point to the right scheduler instance. Explain the situation. Signed-off-by: Tejun Heo Acked-by: Andrea Righi

sched_ext: Add @sch to SCX_CALL_OP*()

2025-05-14T15:11:48Z

In preparation of hierarchical scheduling support, add @sch to scx_exit() and friends: - scx_exit/error() updated to take explicit @sch instead of assuming scx_root. - scx_kf_exit/error() added. These are to be used from kfuncs, don't take @sch and internally determine the scx_sched instance to abort. Currently, it's always scx_root but once multiple scheduler support is in place, it will be the scx_sched instance that invoked the kfunc. This simplifies many callsites and defers scx_sched lookup until error is triggered. - @sch is propagated to ops_cpu_valid() and ops_sanitize_err(). The CPU validity conditions in ops_cpu_valid() are factored into __cpu_valid() to implement kf_cpu_valid() which is the counterpart to scx_kf_exit/error(). - All users are converted. Most conversions are straightforward. check_rq_for_timeouts() and scx_softlockup() are updated to use explicit rcu_dereference*(scx_root) for safety as they may execute asynchronous to the exit path. scx_tick() is also updated to use rcu_dereference(). While not strictly necessary due to the preceding scx_enabled() test and IRQ disabled context, this removes the subtlety at no noticeable cost. No behavior changes intended. Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi

sched_ext: Cleanup [__]scx_exit/error*()

2025-05-14T15:11:48Z

__scx_exit() is the base exit implementation and there are three wrappers on top of it - scx_exit(), __scx_error() and scx_error(). This is more confusing than helpful especially given that there are only a couple users of scx_exit() and __scx_error(). To simplify the situation: - Make __scx_exit() take va_list and rename it to scx_vexit(). This is to ease implementing more complex extensions on top. - Make scx_exit() a varargs wrapper around __scx_exit(). scx_exit() now takes both @kind and @exit_code. - Convert existing scx_exit() and __scx_error() users to use the new scx_exit(). - scx_error() remains unchanged. Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi

sched_ext: Add @sch to SCX_CALL_OP*()

2025-05-14T15:11:48Z

In preparation of hierarchical scheduling support, make SCX_CALL_OP*() take explicit @sch instead of assuming scx_root. As scx_root is still the only scheduler instance, this patch doesn't make any functional changes. Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi

sched_ext: Clean up scx_root usages

2025-05-14T15:11:48Z

- Always cache scx_root into local variable sch before using. - Don't use scx_root if cached sch is available. - Wrap !sch test with unlikely(). - Pass @scx into scx_cgroup_init/exit(). No behavior changes intended. Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi