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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?IUPzvlBrYrJc8RCZFZdGayxVehSJpZmHezAzlV4UMY6X5IMCpeqjEo+Z4umr?= =?us-ascii?Q?2lDm8f129XO4CMrlSvtciGOm6B9bZW+wtdEqF8OAq6fCNfBTsOqUtqYkwuhc?= =?us-ascii?Q?mqEzRBWAKtVQXbCq1PVeZKASDJglMbH05RZeJIwNYK0hrMhK+6QXZF6CVq0+?= =?us-ascii?Q?iVr/zvxCGziZfgJ1280r8AcUTFgARWQ1LbIusT9rQ3xoxC3k69vK6f4h+4LT?= =?us-ascii?Q?l6D8fVMayJAbAxeCEGvpf2CsIoLE7PNSjyvLtklbQaAhJl2EtZgMjlmQSHl/?= =?us-ascii?Q?VX/+OpZoiQvIjIlG0OVIsbkRqPQzvyzaNXvZJws+n9grfN+AL2Bjo5VXa+ys?= =?us-ascii?Q?u6jsyjgx8Mwk8EKCkvRS8hJyI4/LJEYxcFYbSaNQbY+Bs03esQ9bvhuas9Ad?= =?us-ascii?Q?L4PivgVkcEmVkhQ/oOy2evA99JDK2ln9hL8u4TKY2MQn7TE77KEeNWfOGd2E?= =?us-ascii?Q?cIyS8j28O4drN8l67lmnINWweLFEAe5+Pkg6ARUCsssEKEcpz6bF1Egoggl5?= =?us-ascii?Q?1sZkU13CygFGGJyJSYyrBZeEnESUvrJJHHhK4pU24Kxvb4TjQ+5IEXhGEnIJ?= =?us-ascii?Q?vKHPxng5wQqnBj71ebb74L15N4rVSQ0TxbjuIcquDKDEaCNFWlDIpWAY9/kW?= =?us-ascii?Q?7+wY+WzYbtoiHW4D3TC83gkwQtqWz5G9yDFzwb+D+Za1hgGu+oR8NmaA//sz?= =?us-ascii?Q?84Ota85g6eseLVoiWnZL/b+TuUmOXZB7xHF9G7YvQPU2NivbnF5zKdVBJagK?= =?us-ascii?Q?d3n0IUonSEMwDRG/U9Z09wkXaAXv6l5Ta00+S9n17fiKzsso1NftDGQF+WWy?= =?us-ascii?Q?npp010tWNefiUkyp7EAXkrhrnwdprFnBRIW5xcZ3tnY91caOYKzrIKSVE11P?= =?us-ascii?Q?nK7mJYNZN//NDPpVPUCT6wS6E4TaeDuQcxZkhfDTJbrAYyGOp4sKl+ZssqsV?= =?us-ascii?Q?UH9RFJ69T9l/lSG9jclLhS+4uf9rvGa6H7AxuiifYc9Xs12BlQjMg/u0hSfb?= =?us-ascii?Q?DMbYsTMEuYcE70zI4bOBUr4HeKYbJ829b/5giD9ke+0hjp3P1vLwNKP3NFqE?= =?us-ascii?Q?3Ku5JIGhl91FuS/AZoCar505d+6hMn5kolmerbWNpuX5DxHNzxo15kte1KAY?= =?us-ascii?Q?VulgHmanETKgvp9PxBui1M8c2SMY8ONZVXE7uFqnuY+6vjCj/WWBoMKV7dv3?= =?us-ascii?Q?t46Uvf++aMhadzQUv6BwrprzVG7bAtL+GjPxwXHXv/HciyIU0TOCTBqUYHeS?= =?us-ascii?Q?DUch8rgpmkYvu15OJQkMHQy6I7PkRsUTz/oItzC2hzSTT7+AxrSddZ7Lu8w6?= =?us-ascii?Q?6rdfDKuSFcPh4EPmff4P4kNLL63uIfvqqhZCoGfxk9zqzNQJXaiYLKAhSRAO?= =?us-ascii?Q?uhBcNtwfrelbJCLAO0E0I/58PeKy+fk+HGHnAk8aWGq7aiX8InGBYIT+/BDR?= =?us-ascii?Q?D0mV8p5kZV1GEaC0VjsSro8nvxhMkcxLGokkZK1PNvlpDZtPfXpuCIA4cOf7?= =?us-ascii?Q?heUT/0gMq1xLWbZYnnxKfADeRtn2VGS5d5YGrr3LROWP+s9bHXAymtiYoDA6?= =?us-ascii?Q?fFg7f8GxwCKnrCEjcXtBfnKiy0mi0aGLxVsfjofxlIfhxGj6FRbuI8hUKIZ1?= =?us-ascii?Q?vDW4bClA23bIda/i7DBa7WxWC0N2UfIhGH+QNG801i3RnxAEaE840EU4cPTa?= =?us-ascii?Q?VHko6TaG3dIeK+neYIJ8WGXKLrAK5+9osatuPkTqYuqmrdbzRFlnJ1xuL3M2?= =?us-ascii?Q?4c4YCSV1zg=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: e036743e-e764-4416-53b4-08df126ef731 X-MS-Exchange-CrossTenant-AuthSource: DM6PR12MB4827.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Sep 2026 14:46:31.4460 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: j31tLQuXPye1hdarOwLyiVIkxdr0XqpIF12A9uv6K+sG7RX0rpzqCaS2iT4ZdPZV4mB2hcoeQLBxsjM9hnhSVg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA5PPFB9BA66B77 The fair scheduling class can defer a scheduling boundary through lazy rescheduling, but sched_ext currently exposes only immediate preemption to BPF schedulers. This series adds lazy variants of the enqueue and kick preemption flags. They expire the running sched_ext task's slice while allowing the scheduling boundary to be deferred until a return to user space or the next scheduler tick. SCX_OPS_LAZY_SLICE_EXPIRY selects lazy slice expiry by default. Schedulers can override that default in either direction for individual tasks through scx_bpf_task_set_slice_expiry(). The helper preserves sub-scheduler task ownership boundaries. Bypass continues to force immediate rescheduling. Lazy enqueue and kick requests also restore the scheduler tick when targeting an infinite-slice task on a NO_HZ_FULL CPU, ensuring forward progress even when the target's tick has stopped. The selftests cover immediate and lazy preemption, coalescing and precedence between kick modes, enqueue preemption, per-task slice-expiry overrides, invalid flags, and lazy preemption of infinite-slice tasks on NO_HZ_FULL CPUs. Tested in separate virtme-ng runs, covering preempt=lazy and nohz_full: $ vng -a "preempt=lazy" -- tools/testing/selftests/sched_ext/runner -t kick kick: PASSED: 6 SKIPPED: 0 FAILED: 0 $ vng -a "preempt=lazy nohz_full=8-15" -- tools/testing/selftests/sched_ext/runner -t nohz_tick nohz_tick: CPU 8 received 7 finite-slice ticks PASSED: 1 SKIPPED: 0 FAILED: 0 Changes in v3: - Avoid redundant rq clock updates when restoring the tick dependency and use the pinned rq lock helpers for lazy kick delivery (Sashiko). - Set PR_SET_PDEATHSIG for the indefinitely spinning kick test workers so they don't survive unexpected test-runner exit (Sashiko). - Wait for a delta in nr_lazy_victim_running instead of an absolute count that may include reschedules from the previous phase (Sashiko). - Increase the nohz_tick scheduler watchdog and phase timeouts to tolerate scheduling delays in oversubscribed test VMs. - Link to v2: https://lore.kernel.org/r/20260914084955.1798562-1-arighi@nvidia.com Changes in v2: - Make lazy slice expiry a per-task property (Tejun Heo). - Add scx_bpf_task_set_slice_expiry() for per-task overrides from any sched_ext callback (preserving sub-scheduler task ownership). - Restore the scheduler tick dependency for lazy enqueue and kick preemption of infinite-slice tasks on NO_HZ_FULL CPUs (Tejun Heo). - Accumulate immediate and lazy kick requests independently and resolve their precedence in kick_one_cpu() (Tejun Heo). - Allow PREEMPT|PREEMPT_LAZY and WAIT|PREEMPT_LAZY, immediate preemption, WAIT and plain kicks take precedence over lazy preemption (Tejun Heo). - Clear both preemption masks together when processing or skipping a preemption request (Tejun Heo). - Extend the kselftests with combined and ordered kick requests, per-task expiry overrides and NO_HZ_FULL coverage. - Link to v1: https://lore.kernel.org/r/20260911195800.974364-1-arighi@nvidia.com Andrea Righi (2): sched_ext: Add lazy preemption support selftests/sched_ext: Add lazy preemption tests include/linux/sched/ext.h | 8 + kernel/sched/ext/ext.c | 153 +++++-- kernel/sched/ext/internal.h | 39 +- kernel/sched/ext/sub.c | 15 +- tools/sched_ext/include/scx/compat.bpf.h | 13 + tools/sched_ext/include/scx/enum_defs.autogen.h | 3 + tools/sched_ext/include/scx/enums.autogen.bpf.h | 6 + tools/sched_ext/include/scx/enums.autogen.h | 2 + tools/sched_ext/include/scx/enums_abi.autogen.h | 5 +- tools/testing/selftests/sched_ext/Makefile | 1 + tools/testing/selftests/sched_ext/kick.bpf.c | 166 +++++++ tools/testing/selftests/sched_ext/kick.c | 530 ++++++++++++++++++++++ tools/testing/selftests/sched_ext/nohz_tick.bpf.c | 56 ++- tools/testing/selftests/sched_ext/nohz_tick.c | 195 +++++++- 14 files changed, 1143 insertions(+), 49 deletions(-) create mode 100644 tools/testing/selftests/sched_ext/kick.bpf.c create mode 100644 tools/testing/selftests/sched_ext/kick.c