user/sven/linux.git/kernel/sched/idle.c, branch v6.10

Merge tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2024-03-12T02:53:15Z

Pull core x86 updates from Ingo Molnar: - The biggest change is the rework of the percpu code, to support the 'Named Address Spaces' GCC feature, by Uros Bizjak: - This allows C code to access GS and FS segment relative memory via variables declared with such attributes, which allows the compiler to better optimize those accesses than the previous inline assembly code. - The series also includes a number of micro-optimizations for various percpu access methods, plus a number of cleanups of %gs accesses in assembly code. - These changes have been exposed to linux-next testing for the last ~5 months, with no known regressions in this area. - Fix/clean up __switch_to()'s broken but accidentally working handling of FPU switching - which also generates better code - Propagate more RIP-relative addressing in assembly code, to generate slightly better code - Rework the CPU mitigations Kconfig space to be less idiosyncratic, to make it easier for distros to follow & maintain these options - Rework the x86 idle code to cure RCU violations and to clean up the logic - Clean up the vDSO Makefile logic - Misc cleanups and fixes * tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits) x86/idle: Select idle routine only once x86/idle: Let prefer_mwait_c1_over_halt() return bool x86/idle: Cleanup idle_setup() x86/idle: Clean up idle selection x86/idle: Sanitize X86_BUG_AMD_E400 handling sched/idle: Conditionally handle tick broadcast in default_idle_call() x86: Increase brk randomness entropy for 64-bit systems x86/vdso: Move vDSO to mmap region x86/vdso/kbuild: Group non-standard build attributes and primary object file rules together x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o x86/retpoline: Ensure default return thunk isn't used at runtime x86/vdso: Use CONFIG_COMPAT_32 to specify vdso32 x86/vdso: Use $(addprefix ) instead of $(foreach ) x86/vdso: Simplify obj-y addition x86/vdso: Consolidate targets and clean-files x86/bugs: Rename CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK x86/bugs: Rename CONFIG_CPU_SRSO => CONFIG_MITIGATION_SRSO x86/bugs: Rename CONFIG_CPU_IBRS_ENTRY => CONFIG_MITIGATION_IBRS_ENTRY x86/bugs: Rename CONFIG_CPU_UNRET_ENTRY => CONFIG_MITIGATION_UNRET_ENTRY x86/bugs: Rename CONFIG_SLS => CONFIG_MITIGATION_SLS ...

sched/idle: Conditionally handle tick broadcast in default_idle_call()

2024-03-01T20:04:27Z

The x86 architecture has an idle routine for AMD CPUs which are affected by erratum 400. On the affected CPUs the local APIC timer stops in the C1E halt state. It therefore requires tick broadcasting. The invocation of tick_broadcast_enter()/exit() from this function violates the RCU constraints because it can end up in lockdep or tracing, which rightfully triggers a warning. tick_broadcast_enter()/exit() must be invoked before ct_cpuidle_enter() and after ct_cpuidle_exit() in default_idle_call(). Add a static branch conditional invocation of tick_broadcast_enter()/exit() into this function to allow X86 to replace the AMD specific idle code. It's guarded by a config switch which will be selected by x86. Otherwise it's a NOOP. Reported-by: Borislav Petkov Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20240229142248.266708822@linutronix.de

tick: Assume timekeeping is correctly handed over upon last offline idle call

2024-02-26T10:37:32Z

The timekeeping duty is handed over from the outgoing CPU on stop machine, then the oneshot tick is stopped right after. Therefore it's guaranteed that the current CPU isn't the timekeeper upon its last call to idle. Besides, calling tick_nohz_idle_stop_tick() while the dying CPU goes into idle suggests that the tick is going to be stopped while it is actually stopped already from the appropriate CPU hotplug state. Remove the confusing call and the obsolete case handling and convert it to a sanity check that verifies the above assumption. Signed-off-by: Frederic Weisbecker Signed-off-by: Thomas Gleixner Reviewed-by: Thomas Gleixner Link: https://lore.kernel.org/r/20240225225508.11587-16-frederic@kernel.org

sched/cpuidle: Comment about timers requirements VS idle handler

2023-11-15T08:57:51Z

Add missing explanation concerning IRQs re-enablement constraints in the cpuidle path against timers. Signed-off-by: Frederic Weisbecker Signed-off-by: Peter Zijlstra (Intel) Acked-by: Rafael J. Wysocki Link: https://lkml.kernel.org/r/20231114193840.4041-2-frederic@kernel.org

Merge branch 'sched/urgent' into sched/core, to pick up fixes and refresh the branch

2023-10-07T09:32:24Z

Signed-off-by: Ingo Molnar

kernel/sched: Modify initial boot task idle setup

2023-09-19T08:48:04Z

Initial booting is setting the task flag to idle (PF_IDLE) by the call path sched_init() -> init_idle(). Having the task idle and calling call_rcu() in kernel/rcu/tiny.c means that TIF_NEED_RESCHED will be set. Subsequent calls to any cond_resched() will enable IRQs, potentially earlier than the IRQ setup has completed. Recent changes have caused just this scenario and IRQs have been enabled early. This causes a warning later in start_kernel() as interrupts are enabled before they are fully set up. Fix this issue by setting the PF_IDLE flag later in the boot sequence. Although the boot task was marked as idle since (at least) d80e4fda576d, I am not sure that it is wrong to do so. The forced context-switch on idle task was introduced in the tiny_rcu update, so I'm going to claim this fixes 5f6130fa52ee. Fixes: 5f6130fa52ee ("tiny_rcu: Directly force QS when call_rcu_[bh|sched]() on idle_task") Signed-off-by: Liam R. Howlett Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/linux-mm/CAMuHMdWpvpWoDa=Ox-do92czYRvkok6_x6pYUH+ZouMcJbXy+Q@mail.gmail.com/

sched/fair: Rename check_preempt_curr() to wakeup_preempt()

2023-09-19T08:40:10Z

The name is a bit opaque - make it clear that this is about wakeup preemption. Also rename the ->check_preempt_curr() methods similarly. Signed-off-by: Ingo Molnar Acked-by: Peter Zijlstra (Intel)

sched/idle: Mark arch_cpu_idle_dead() __noreturn

2023-03-08T16:44:28Z

Before commit 076cbf5d2163 ("x86/xen: don't let xen_pv_play_dead() return"), in Xen, when a previously offlined CPU was brought back online, it unexpectedly resumed execution where it left off in the middle of the idle loop. There were some hacks to make that work, but the behavior was surprising as do_idle() doesn't expect an offlined CPU to return from the dead (in arch_cpu_idle_dead()). Now that Xen has been fixed, and the arch-specific implementations of arch_cpu_idle_dead() also don't return, give it a __noreturn attribute. This will cause the compiler to complain if an arch-specific implementation might return. It also improves code generation for both caller and callee. Also fixes the following warning: vmlinux.o: warning: objtool: do_idle+0x25f: unreachable instruction Reported-by: Paul E. McKenney Tested-by: Paul E. McKenney Link: https://lore.kernel.org/r/60d527353da8c99d4cf13b6473131d46719ed16d.1676358308.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf

sched/idle: Make sure weak version of arch_cpu_idle_dead() doesn't return

2023-03-08T16:44:27Z

arch_cpu_idle_dead() should never return. Make it so. Link: https://lore.kernel.org/r/cf5ad95eef50f7704bb30e7770c59bfe23372af7.1676358308.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf

arch/idle: Change arch_cpu_idle() behavior: always exit with IRQs disabled

2023-01-13T10:48:15Z

Current arch_cpu_idle() is called with IRQs disabled, but will return with IRQs enabled. However, the very first thing the generic code does after calling arch_cpu_idle() is raw_local_irq_disable(). This means that architectures that can idle with IRQs disabled end up doing a pointless 'enable-disable' dance. Therefore, push this IRQ disabling into the idle function, meaning that those architectures can avoid the pointless IRQ state flipping. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Tested-by: Tony Lindgren Tested-by: Ulf Hansson Reviewed-by: Gautham R. Shenoy Acked-by: Mark Rutland [arm64] Acked-by: Rafael J. Wysocki Acked-by: Guo Ren Acked-by: Frederic Weisbecker Link: https://lore.kernel.org/r/20230112195540.618076436@infradead.org