user/sven/linux.git/kernel/smp.c, branch v6.1.57

Merge tag 'bitmap-6.1-rc1' of https://github.com/norov/linux

2022-10-10T19:49:34Z

Pull bitmap updates from Yury Norov: - Fix unsigned comparison to -1 in CPUMAP_FILE_MAX_BYTES (Phil Auld) - cleanup nr_cpu_ids vs nr_cpumask_bits mess (me) This series cleans that mess and adds new config FORCE_NR_CPUS that allows to optimize cpumask subsystem if the number of CPUs is known at compile-time. - optimize find_bit() functions (me) Reworks find_bit() functions based on new FIND_{FIRST,NEXT}_BIT() macros. - add find_nth_bit() (me) Adds find_nth_bit(), which is ~70 times faster than bitcounting with for_each() loop: for_each_set_bit(bit, mask, size) if (n-- == 0) return bit; Also adds bitmap_weight_and() to let people replace this pattern: tmp = bitmap_alloc(nbits); bitmap_and(tmp, map1, map2, nbits); weight = bitmap_weight(tmp, nbits); bitmap_free(tmp); with a single bitmap_weight_and() call. - repair cpumask_check() (me) After switching cpumask to use nr_cpu_ids, cpumask_check() started generating many false-positive warnings. This series fixes it. - Add for_each_cpu_andnot() and for_each_cpu_andnot() (Valentin Schneider) Extends the API with one more function and applies it in sched/core. * tag 'bitmap-6.1-rc1' of https://github.com/norov/linux: (28 commits) sched/core: Merge cpumask_andnot()+for_each_cpu() into for_each_cpu_andnot() lib/test_cpumask: Add for_each_cpu_and(not) tests cpumask: Introduce for_each_cpu_andnot() lib/find_bit: Introduce find_next_andnot_bit() cpumask: fix checking valid cpu range lib/bitmap: add tests for for_each() loops lib/find: optimize for_each() macros lib/bitmap: introduce for_each_set_bit_wrap() macro lib/find_bit: add find_next{,_and}_bit_wrap cpumask: switch for_each_cpu{,_not} to use for_each_bit() net: fix cpu_max_bits_warn() usage in netif_attrmask_next{,_and} cpumask: add cpumask_nth_{,and,andnot} lib/bitmap: remove bitmap_ord_to_pos lib/bitmap: add tests for find_nth_bit() lib: add find_nth{,_and,_andnot}_bit() lib/bitmap: add bitmap_weight_and() lib/bitmap: don't call __bitmap_weight() in kernel code tools: sync find_bit() implementation lib/find_bit: optimize find_next_bit() functions lib/find_bit: create find_first_zero_bit_le() ...

lib/cpumask: add FORCE_NR_CPUS config option

2022-09-20T23:11:44Z

The size of cpumasks is hard-limited by compile-time parameter NR_CPUS, but defined at boot-time when kernel parses ACPI/DT tables, and stored in nr_cpu_ids. In many practical cases, number of CPUs for a target is known at compile time, and can be provided with NR_CPUS. In that case, compiler may be instructed to rely on NR_CPUS as on actual number of CPUs, not an upper limit. It allows to optimize many cpumask routines and significantly shrink size of the kernel image. This patch adds FORCE_NR_CPUS option to teach the compiler to rely on NR_CPUS and enable corresponding optimizations. If FORCE_NR_CPUS=y, kernel will not set nr_cpu_ids at boot, but only check that the actual number of possible CPUs is equal to NR_CPUS, and WARN if that doesn't hold. The new option is especially useful in embedded applications because kernel configurations are unique for each SoC, the number of CPUs is constant and known well, and memory limitations are typically harder. For my 4-CPU ARM64 build with NR_CPUS=4, FORCE_NR_CPUS=y saves 46KB: add/remove: 3/4 grow/shrink: 46/729 up/down: 652/-46952 (-46300) Signed-off-by: Yury Norov

smp: add set_nr_cpu_ids()

2022-09-20T00:51:53Z

In preparation to support compile-time nr_cpu_ids, add a setter for the variable. This is a no-op for all arches. Signed-off-by: Yury Norov

smp: don't declare nr_cpu_ids if NR_CPUS == 1

2022-09-20T00:51:53Z

SMP and NR_CPUS are independent options, hence nr_cpu_ids may be declared even if NR_CPUS == 1, which is useless. Signed-off-by: Yury Norov

sched/debug: Try trigger_single_cpu_backtrace(cpu) in dump_cpu_task()

2022-08-31T12:03:14Z

The trigger_all_cpu_backtrace() function attempts to send an NMI to the target CPU, which usually provides much better stack traces than the dump_cpu_task() function's approach of dumping that stack from some other CPU. So much so that most calls to dump_cpu_task() only happen after a call to trigger_all_cpu_backtrace() has failed. And the exception to this rule really should attempt to use trigger_all_cpu_backtrace() first. Therefore, move the trigger_all_cpu_backtrace() invocation into dump_cpu_task(). Signed-off-by: Zhen Lei Signed-off-by: Paul E. McKenney Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Vincent Guittot Cc: Dietmar Eggemann Cc: Ben Segall Cc: Mel Gorman Cc: Daniel Bristot de Oliveira Cc: Valentin Schneider

locking/csd_lock: Change csdlock_debug from early_param to __setup

2022-07-19T18:40:00Z

The csdlock_debug kernel-boot parameter is parsed by the early_param() function csdlock_debug(). If set, csdlock_debug() invokes static_branch_enable() to enable csd_lock_wait feature, which triggers a panic on arm64 for kernels built with CONFIG_SPARSEMEM=y and CONFIG_SPARSEMEM_VMEMMAP=n. With CONFIG_SPARSEMEM_VMEMMAP=n, __nr_to_section is called in static_key_enable() and returns NULL, resulting in a NULL dereference because mem_section is initialized only later in sparse_init(). This is also a problem for powerpc because early_param() functions are invoked earlier than jump_label_init(), also resulting in static_key_enable() failures. These failures cause the warning "static key 'xxx' used before call to jump_label_init()". Thus, early_param is too early for csd_lock_wait to run static_branch_enable(), so changes it to __setup to fix these. Fixes: 8d0968cc6b8f ("locking/csd_lock: Add boot parameter for controlling CSD lock debugging") Cc: stable@vger.kernel.org Reported-by: Chen jingwen Signed-off-by: Chen Zhongjin Signed-off-by: Paul E. McKenney

Merge tag 'sched-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2022-05-24T18:11:13Z

Pull scheduler updates from Ingo Molnar: - Updates to scheduler metrics: - PELT fixes & enhancements - PSI fixes & enhancements - Refactor cpu_util_without() - Updates to instrumentation/debugging: - Remove sched_trace_*() helper functions - can be done via debug info - Fix double update_rq_clock() warnings - Introduce & use "preemption model accessors" to simplify some of the Kconfig complexity. - Make softirq handling RT-safe. - Misc smaller fixes & cleanups. * tag 'sched-core-2022-05-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: topology: Remove unused cpu_cluster_mask() sched: Reverse sched_class layout sched/deadline: Remove superfluous rq clock update in push_dl_task() sched/core: Avoid obvious double update_rq_clock warning smp: Make softirq handling RT safe in flush_smp_call_function_queue() smp: Rename flush_smp_call_function_from_idle() sched: Fix missing prototype warnings sched/fair: Remove cfs_rq_tg_path() sched/fair: Remove sched_trace_*() helper functions sched/fair: Refactor cpu_util_without() sched/fair: Revise comment about lb decision matrix sched/psi: report zeroes for CPU full at the system level sched/fair: Delete useless condition in tg_unthrottle_up() sched/fair: Fix cfs_rq_clock_pelt() for throttled cfs_rq sched/fair: Move calculate of avg_load to a better location mailmap: Update my email address to @redhat.com MAINTAINERS: Add myself as scheduler topology reviewer psi: Fix trigger being fired unexpectedly at initial ftrace: Use preemption model accessors for trace header printout kcsan: Use preemption model accessors

Merge tag 'rcu.2022.05.19a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

2022-05-23T18:46:51Z

Pull RCU update from Paul McKenney: - Documentation updates - Miscellaneous fixes - Callback-offloading updates, mainly simplifications - RCU-tasks updates, including some -rt fixups, handling of systems with sparse CPU numbering, and a fix for a boot-time race-condition failure - Put SRCU on a memory diet in order to reduce the size of the srcu_struct structure - Torture-test updates fixing some bugs in tests and closing some testing holes - Torture-test updates for the RCU tasks flavors, most notably ensuring that building rcutorture and friends does not change the RCU-tasks-related Kconfig options - Torture-test scripting updates - Expedited grace-period updates, most notably providing milliseconds-scale (not all that) soft real-time response from synchronize_rcu_expedited(). This is also the first time in almost 30 years of RCU that someone other than me has pushed for a reduction in the RCU CPU stall-warning timeout, in this case by more than three orders of magnitude from 21 seconds to 20 milliseconds. This tighter timeout applies only to expedited grace periods * tag 'rcu.2022.05.19a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (80 commits) rcu: Move expedited grace period (GP) work to RT kthread_worker rcu: Introduce CONFIG_RCU_EXP_CPU_STALL_TIMEOUT srcu: Drop needless initialization of sdp in srcu_gp_start() srcu: Prevent expedited GPs and blocking readers from consuming CPU srcu: Add contention check to call_srcu() srcu_data ->lock acquisition srcu: Automatically determine size-transition strategy at boot rcutorture: Make torture.sh allow for --kasan rcutorture: Make torture.sh refscale and rcuscale specify Tasks Trace RCU rcutorture: Make kvm.sh allow more memory for --kasan runs torture: Save "make allmodconfig" .config file scftorture: Remove extraneous "scf" from per_version_boot_params rcutorture: Adjust scenarios' Kconfig options for CONFIG_PREEMPT_DYNAMIC torture: Enable CSD-lock stall reports for scftorture torture: Skip vmlinux check for kvm-again.sh runs scftorture: Adjust for TASKS_RCU Kconfig option being selected rcuscale: Allow rcuscale without RCU Tasks Rude/Trace rcuscale: Allow rcuscale without RCU Tasks refscale: Allow refscale without RCU Tasks Rude/Trace refscale: Allow refscale without RCU Tasks rcutorture: Allow specifying per-scenario stat_interval ...

Merge tag 'v5.18-rc5' into sched/core to pull in fixes & to resolve a conflict

2022-05-06T08:21:46Z

- sched/core is on a pretty old -rc1 base - refresh it to include recent fixes. - this also allows up to resolve a (trivial) .mailmap conflict Conflicts: .mailmap Signed-off-by: Ingo Molnar

smp: Make softirq handling RT safe in flush_smp_call_function_queue()

2022-05-01T08:03:43Z

flush_smp_call_function_queue() invokes do_softirq() which is not available on PREEMPT_RT. flush_smp_call_function_queue() is invoked from the idle task and the migration task with preemption or interrupts disabled. So RT kernels cannot process soft interrupts in that context as that has to acquire 'sleeping spinlocks' which is not possible with preemption or interrupts disabled and forbidden from the idle task anyway. The currently known SMP function call which raises a soft interrupt is in the block layer, but this functionality is not enabled on RT kernels due to latency and performance reasons. RT could wake up ksoftirqd unconditionally, but this wants to be avoided if there were soft interrupts pending already when this is invoked in the context of the migration task. The migration task might have preempted a threaded interrupt handler which raised a soft interrupt, but did not reach the local_bh_enable() to process it. The "running" ksoftirqd might prevent the handling in the interrupt thread context which is causing latency issues. Add a new function which handles this case explicitely for RT and falls back to do_softirq() on !RT kernels. In the RT case this warns when one of the flushed SMP function calls raised a soft interrupt so this can be investigated. [ tglx: Moved the RT part out of SMP code ] Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/YgKgL6aPj8aBES6G@linutronix.de Link: https://lore.kernel.org/r/20220413133024.356509586@linutronix.de