Add an API for user threads to request scheduler to not delay
scheduling it when woken up to run. This is allowed only for RT threads.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Prakash Sangappa <prakash.sangappa@oracle.com>
---
include/linux/sched.h | 1 +
include/uapi/linux/prctl.h | 3 +++
kernel/sys.c | 18 ++++++++++++++++++
3 files changed, 22 insertions(+)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5c5868c555f0..3e8eb64658d1 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1062,6 +1062,7 @@ struct task_struct {
#endif
unsigned in_nf_duplicate:1;
unsigned rseq_delay_resched:2;
+ unsigned sched_nodelay:1;
#ifdef CONFIG_PREEMPT_RT
struct netdev_xmit net_xmit;
#endif
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 6f9912c65595..907300cd4469 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -379,4 +379,7 @@ struct prctl_mm_map {
# define PR_FUTEX_HASH_GET_SLOTS 2
# define PR_FUTEX_HASH_GET_IMMUTABLE 3
+/* TASK sched nodelay request */
+#define PR_SET_SCHED_NODELAY 79
+#define PR_GET_SCHED_NODELAY 80
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index a088a6b1ac23..2f8b4512c6e4 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2890,6 +2890,24 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
case PR_FUTEX_HASH:
error = futex_hash_prctl(arg2, arg3, arg4);
break;
+ case PR_SET_SCHED_NODELAY:
+ if (arg3 || arg4 || arg5)
+ return -EINVAL;
+ if (current->sched_class != &rt_sched_class)
+ return -EINVAL;
+ if (arg2)
+ current->sched_nodelay = 1;
+ else
+ current->sched_nodelay = 0;
+ break;
+ case PR_GET_SCHED_NODELAY:
+ if (arg2 || arg3 || arg4 || arg5)
+ return -EINVAL;
+ if (current->sched_class != &rt_sched_class)
+ return -EINVAL;
+ error = (current->sched_nodelay == 1);
+ break;
+
default:
trace_task_prctl_unknown(option, arg2, arg3, arg4, arg5);
error = -EINVAL;
--
2.43.5Hi Prakash,
kernel test robot noticed the following build errors:
[auto build test ERROR on tip/x86/core]
[also build test ERROR on linus/master v6.16-rc7]
[cannot apply to tip/sched/core tip/core/entry next-20250725]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Prakash-Sangappa/sched-Scheduler-time-slice-extension/20250725-002052
base: tip/x86/core
patch link: https://lore.kernel.org/r/20250724161625.2360309-8-prakash.sangappa%40oracle.com
patch subject: [PATCH V7 07/11] sched: Add API to indicate not to delay scheduling
config: riscv-randconfig-001-20250725 (https://download.01.org/0day-ci/archive/20250725/202507252250.gOKHNKiq-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 10.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250725/202507252250.gOKHNKiq-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202507252250.gOKHNKiq-lkp@intel.com/
All errors (new ones prefixed by >>):
kernel/sys.c: In function '__do_sys_prctl':
>> kernel/sys.c:2830:32: error: 'rt_sched_class' undeclared (first use in this function); did you mean 'sched_class'?
2830 | if (current->sched_class != &rt_sched_class)
| ^~~~~~~~~~~~~~
| sched_class
kernel/sys.c:2830:32: note: each undeclared identifier is reported only once for each function it appears in
vim +2830 kernel/sys.c
2473
2474 SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
2475 unsigned long, arg4, unsigned long, arg5)
2476 {
2477 struct task_struct *me = current;
2478 unsigned char comm[sizeof(me->comm)];
2479 long error;
2480
2481 error = security_task_prctl(option, arg2, arg3, arg4, arg5);
2482 if (error != -ENOSYS)
2483 return error;
2484
2485 error = 0;
2486 switch (option) {
2487 case PR_SET_PDEATHSIG:
2488 if (!valid_signal(arg2)) {
2489 error = -EINVAL;
2490 break;
2491 }
2492 me->pdeath_signal = arg2;
2493 break;
2494 case PR_GET_PDEATHSIG:
2495 error = put_user(me->pdeath_signal, (int __user *)arg2);
2496 break;
2497 case PR_GET_DUMPABLE:
2498 error = get_dumpable(me->mm);
2499 break;
2500 case PR_SET_DUMPABLE:
2501 if (arg2 != SUID_DUMP_DISABLE && arg2 != SUID_DUMP_USER) {
2502 error = -EINVAL;
2503 break;
2504 }
2505 set_dumpable(me->mm, arg2);
2506 break;
2507
2508 case PR_SET_UNALIGN:
2509 error = SET_UNALIGN_CTL(me, arg2);
2510 break;
2511 case PR_GET_UNALIGN:
2512 error = GET_UNALIGN_CTL(me, arg2);
2513 break;
2514 case PR_SET_FPEMU:
2515 error = SET_FPEMU_CTL(me, arg2);
2516 break;
2517 case PR_GET_FPEMU:
2518 error = GET_FPEMU_CTL(me, arg2);
2519 break;
2520 case PR_SET_FPEXC:
2521 error = SET_FPEXC_CTL(me, arg2);
2522 break;
2523 case PR_GET_FPEXC:
2524 error = GET_FPEXC_CTL(me, arg2);
2525 break;
2526 case PR_GET_TIMING:
2527 error = PR_TIMING_STATISTICAL;
2528 break;
2529 case PR_SET_TIMING:
2530 if (arg2 != PR_TIMING_STATISTICAL)
2531 error = -EINVAL;
2532 break;
2533 case PR_SET_NAME:
2534 comm[sizeof(me->comm) - 1] = 0;
2535 if (strncpy_from_user(comm, (char __user *)arg2,
2536 sizeof(me->comm) - 1) < 0)
2537 return -EFAULT;
2538 set_task_comm(me, comm);
2539 proc_comm_connector(me);
2540 break;
2541 case PR_GET_NAME:
2542 get_task_comm(comm, me);
2543 if (copy_to_user((char __user *)arg2, comm, sizeof(comm)))
2544 return -EFAULT;
2545 break;
2546 case PR_GET_ENDIAN:
2547 error = GET_ENDIAN(me, arg2);
2548 break;
2549 case PR_SET_ENDIAN:
2550 error = SET_ENDIAN(me, arg2);
2551 break;
2552 case PR_GET_SECCOMP:
2553 error = prctl_get_seccomp();
2554 break;
2555 case PR_SET_SECCOMP:
2556 error = prctl_set_seccomp(arg2, (char __user *)arg3);
2557 break;
2558 case PR_GET_TSC:
2559 error = GET_TSC_CTL(arg2);
2560 break;
2561 case PR_SET_TSC:
2562 error = SET_TSC_CTL(arg2);
2563 break;
2564 case PR_TASK_PERF_EVENTS_DISABLE:
2565 error = perf_event_task_disable();
2566 break;
2567 case PR_TASK_PERF_EVENTS_ENABLE:
2568 error = perf_event_task_enable();
2569 break;
2570 case PR_GET_TIMERSLACK:
2571 if (current->timer_slack_ns > ULONG_MAX)
2572 error = ULONG_MAX;
2573 else
2574 error = current->timer_slack_ns;
2575 break;
2576 case PR_SET_TIMERSLACK:
2577 if (rt_or_dl_task_policy(current))
2578 break;
2579 if (arg2 <= 0)
2580 current->timer_slack_ns =
2581 current->default_timer_slack_ns;
2582 else
2583 current->timer_slack_ns = arg2;
2584 break;
2585 case PR_MCE_KILL:
2586 if (arg4 | arg5)
2587 return -EINVAL;
2588 switch (arg2) {
2589 case PR_MCE_KILL_CLEAR:
2590 if (arg3 != 0)
2591 return -EINVAL;
2592 current->flags &= ~PF_MCE_PROCESS;
2593 break;
2594 case PR_MCE_KILL_SET:
2595 current->flags |= PF_MCE_PROCESS;
2596 if (arg3 == PR_MCE_KILL_EARLY)
2597 current->flags |= PF_MCE_EARLY;
2598 else if (arg3 == PR_MCE_KILL_LATE)
2599 current->flags &= ~PF_MCE_EARLY;
2600 else if (arg3 == PR_MCE_KILL_DEFAULT)
2601 current->flags &=
2602 ~(PF_MCE_EARLY|PF_MCE_PROCESS);
2603 else
2604 return -EINVAL;
2605 break;
2606 default:
2607 return -EINVAL;
2608 }
2609 break;
2610 case PR_MCE_KILL_GET:
2611 if (arg2 | arg3 | arg4 | arg5)
2612 return -EINVAL;
2613 if (current->flags & PF_MCE_PROCESS)
2614 error = (current->flags & PF_MCE_EARLY) ?
2615 PR_MCE_KILL_EARLY : PR_MCE_KILL_LATE;
2616 else
2617 error = PR_MCE_KILL_DEFAULT;
2618 break;
2619 case PR_SET_MM:
2620 error = prctl_set_mm(arg2, arg3, arg4, arg5);
2621 break;
2622 case PR_GET_TID_ADDRESS:
2623 error = prctl_get_tid_address(me, (int __user * __user *)arg2);
2624 break;
2625 case PR_SET_CHILD_SUBREAPER:
2626 me->signal->is_child_subreaper = !!arg2;
2627 if (!arg2)
2628 break;
2629
2630 walk_process_tree(me, propagate_has_child_subreaper, NULL);
2631 break;
2632 case PR_GET_CHILD_SUBREAPER:
2633 error = put_user(me->signal->is_child_subreaper,
2634 (int __user *)arg2);
2635 break;
2636 case PR_SET_NO_NEW_PRIVS:
2637 if (arg2 != 1 || arg3 || arg4 || arg5)
2638 return -EINVAL;
2639
2640 task_set_no_new_privs(current);
2641 break;
2642 case PR_GET_NO_NEW_PRIVS:
2643 if (arg2 || arg3 || arg4 || arg5)
2644 return -EINVAL;
2645 return task_no_new_privs(current) ? 1 : 0;
2646 case PR_GET_THP_DISABLE:
2647 if (arg2 || arg3 || arg4 || arg5)
2648 return -EINVAL;
2649 error = !!test_bit(MMF_DISABLE_THP, &me->mm->flags);
2650 break;
2651 case PR_SET_THP_DISABLE:
2652 if (arg3 || arg4 || arg5)
2653 return -EINVAL;
2654 if (mmap_write_lock_killable(me->mm))
2655 return -EINTR;
2656 if (arg2)
2657 set_bit(MMF_DISABLE_THP, &me->mm->flags);
2658 else
2659 clear_bit(MMF_DISABLE_THP, &me->mm->flags);
2660 mmap_write_unlock(me->mm);
2661 break;
2662 case PR_MPX_ENABLE_MANAGEMENT:
2663 case PR_MPX_DISABLE_MANAGEMENT:
2664 /* No longer implemented: */
2665 return -EINVAL;
2666 case PR_SET_FP_MODE:
2667 error = SET_FP_MODE(me, arg2);
2668 break;
2669 case PR_GET_FP_MODE:
2670 error = GET_FP_MODE(me);
2671 break;
2672 case PR_SVE_SET_VL:
2673 error = SVE_SET_VL(arg2);
2674 break;
2675 case PR_SVE_GET_VL:
2676 error = SVE_GET_VL();
2677 break;
2678 case PR_SME_SET_VL:
2679 error = SME_SET_VL(arg2);
2680 break;
2681 case PR_SME_GET_VL:
2682 error = SME_GET_VL();
2683 break;
2684 case PR_GET_SPECULATION_CTRL:
2685 if (arg3 || arg4 || arg5)
2686 return -EINVAL;
2687 error = arch_prctl_spec_ctrl_get(me, arg2);
2688 break;
2689 case PR_SET_SPECULATION_CTRL:
2690 if (arg4 || arg5)
2691 return -EINVAL;
2692 error = arch_prctl_spec_ctrl_set(me, arg2, arg3);
2693 break;
2694 case PR_PAC_RESET_KEYS:
2695 if (arg3 || arg4 || arg5)
2696 return -EINVAL;
2697 error = PAC_RESET_KEYS(me, arg2);
2698 break;
2699 case PR_PAC_SET_ENABLED_KEYS:
2700 if (arg4 || arg5)
2701 return -EINVAL;
2702 error = PAC_SET_ENABLED_KEYS(me, arg2, arg3);
2703 break;
2704 case PR_PAC_GET_ENABLED_KEYS:
2705 if (arg2 || arg3 || arg4 || arg5)
2706 return -EINVAL;
2707 error = PAC_GET_ENABLED_KEYS(me);
2708 break;
2709 case PR_SET_TAGGED_ADDR_CTRL:
2710 if (arg3 || arg4 || arg5)
2711 return -EINVAL;
2712 error = SET_TAGGED_ADDR_CTRL(arg2);
2713 break;
2714 case PR_GET_TAGGED_ADDR_CTRL:
2715 if (arg2 || arg3 || arg4 || arg5)
2716 return -EINVAL;
2717 error = GET_TAGGED_ADDR_CTRL();
2718 break;
2719 case PR_SET_IO_FLUSHER:
2720 if (!capable(CAP_SYS_RESOURCE))
2721 return -EPERM;
2722
2723 if (arg3 || arg4 || arg5)
2724 return -EINVAL;
2725
2726 if (arg2 == 1)
2727 current->flags |= PR_IO_FLUSHER;
2728 else if (!arg2)
2729 current->flags &= ~PR_IO_FLUSHER;
2730 else
2731 return -EINVAL;
2732 break;
2733 case PR_GET_IO_FLUSHER:
2734 if (!capable(CAP_SYS_RESOURCE))
2735 return -EPERM;
2736
2737 if (arg2 || arg3 || arg4 || arg5)
2738 return -EINVAL;
2739
2740 error = (current->flags & PR_IO_FLUSHER) == PR_IO_FLUSHER;
2741 break;
2742 case PR_SET_SYSCALL_USER_DISPATCH:
2743 error = set_syscall_user_dispatch(arg2, arg3, arg4,
2744 (char __user *) arg5);
2745 break;
2746 #ifdef CONFIG_SCHED_CORE
2747 case PR_SCHED_CORE:
2748 error = sched_core_share_pid(arg2, arg3, arg4, arg5);
2749 break;
2750 #endif
2751 case PR_SET_MDWE:
2752 error = prctl_set_mdwe(arg2, arg3, arg4, arg5);
2753 break;
2754 case PR_GET_MDWE:
2755 error = prctl_get_mdwe(arg2, arg3, arg4, arg5);
2756 break;
2757 case PR_PPC_GET_DEXCR:
2758 if (arg3 || arg4 || arg5)
2759 return -EINVAL;
2760 error = PPC_GET_DEXCR_ASPECT(me, arg2);
2761 break;
2762 case PR_PPC_SET_DEXCR:
2763 if (arg4 || arg5)
2764 return -EINVAL;
2765 error = PPC_SET_DEXCR_ASPECT(me, arg2, arg3);
2766 break;
2767 case PR_SET_VMA:
2768 error = prctl_set_vma(arg2, arg3, arg4, arg5);
2769 break;
2770 case PR_GET_AUXV:
2771 if (arg4 || arg5)
2772 return -EINVAL;
2773 error = prctl_get_auxv((void __user *)arg2, arg3);
2774 break;
2775 #ifdef CONFIG_KSM
2776 case PR_SET_MEMORY_MERGE:
2777 if (arg3 || arg4 || arg5)
2778 return -EINVAL;
2779 if (mmap_write_lock_killable(me->mm))
2780 return -EINTR;
2781
2782 if (arg2)
2783 error = ksm_enable_merge_any(me->mm);
2784 else
2785 error = ksm_disable_merge_any(me->mm);
2786 mmap_write_unlock(me->mm);
2787 break;
2788 case PR_GET_MEMORY_MERGE:
2789 if (arg2 || arg3 || arg4 || arg5)
2790 return -EINVAL;
2791
2792 error = !!test_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
2793 break;
2794 #endif
2795 case PR_RISCV_V_SET_CONTROL:
2796 error = RISCV_V_SET_CONTROL(arg2);
2797 break;
2798 case PR_RISCV_V_GET_CONTROL:
2799 error = RISCV_V_GET_CONTROL();
2800 break;
2801 case PR_RISCV_SET_ICACHE_FLUSH_CTX:
2802 error = RISCV_SET_ICACHE_FLUSH_CTX(arg2, arg3);
2803 break;
2804 case PR_GET_SHADOW_STACK_STATUS:
2805 if (arg3 || arg4 || arg5)
2806 return -EINVAL;
2807 error = arch_get_shadow_stack_status(me, (unsigned long __user *) arg2);
2808 break;
2809 case PR_SET_SHADOW_STACK_STATUS:
2810 if (arg3 || arg4 || arg5)
2811 return -EINVAL;
2812 error = arch_set_shadow_stack_status(me, arg2);
2813 break;
2814 case PR_LOCK_SHADOW_STACK_STATUS:
2815 if (arg3 || arg4 || arg5)
2816 return -EINVAL;
2817 error = arch_lock_shadow_stack_status(me, arg2);
2818 break;
2819 case PR_TIMER_CREATE_RESTORE_IDS:
2820 if (arg3 || arg4 || arg5)
2821 return -EINVAL;
2822 error = posixtimer_create_prctl(arg2);
2823 break;
2824 case PR_FUTEX_HASH:
2825 error = futex_hash_prctl(arg2, arg3, arg4);
2826 break;
2827 case PR_SET_SCHED_NODELAY:
2828 if (arg3 || arg4 || arg5)
2829 return -EINVAL;
> 2830 if (current->sched_class != &rt_sched_class)
2831 return -EINVAL;
2832 if (arg2)
2833 current->sched_nodelay = 1;
2834 else
2835 current->sched_nodelay = 0;
2836 break;
2837 case PR_GET_SCHED_NODELAY:
2838 if (arg2 || arg3 || arg4 || arg5)
2839 return -EINVAL;
2840 if (current->sched_class != &rt_sched_class)
2841 return -EINVAL;
2842 error = (current->sched_nodelay == 1);
2843 break;
2844
2845 default:
2846 trace_task_prctl_unknown(option, arg2, arg3, arg4, arg5);
2847 error = -EINVAL;
2848 break;
2849 }
2850 return error;
2851 }
2852
--
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