From 16bf5a5e1ec56474ed2a19d72f272ed09a5d3ea1 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 13 Apr 2022 15:31:03 +0200 Subject: [PATCH] smp: Rename flush_smp_call_function_from_idle() This is invoked from the stopper thread too, which is definitely not idle. Rename it to flush_smp_call_function_queue() and fixup the callers. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20220413133024.305001096@linutronix.de --- kernel/sched/core.c | 2 +- kernel/sched/idle.c | 2 +- kernel/sched/smp.h | 4 ++-- kernel/smp.c | 27 ++++++++++++++++++++------- 4 files changed, 24 insertions(+), 11 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e644578bc871..07bacb050198 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2411,7 +2411,7 @@ static int migration_cpu_stop(void *data) * __migrate_task() such that we will not miss enforcing cpus_ptr * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test. */ - flush_smp_call_function_from_idle(); + flush_smp_call_function_queue(); raw_spin_lock(&p->pi_lock); rq_lock(rq, &rf); diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 8f8b5020e76a..60295dbe0d62 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -327,7 +327,7 @@ static void do_idle(void) * RCU relies on this call to be done outside of an RCU read-side * critical section. */ - flush_smp_call_function_from_idle(); + flush_smp_call_function_queue(); schedule_idle(); if (unlikely(klp_patch_pending(current))) diff --git a/kernel/sched/smp.h b/kernel/sched/smp.h index 5719bf9280e9..2eb23dd0f285 100644 --- a/kernel/sched/smp.h +++ b/kernel/sched/smp.h @@ -9,7 +9,7 @@ extern void sched_ttwu_pending(void *arg); extern void send_call_function_single_ipi(int cpu); #ifdef CONFIG_SMP -extern void flush_smp_call_function_from_idle(void); +extern void flush_smp_call_function_queue(void); #else -static inline void flush_smp_call_function_from_idle(void) { } +static inline void flush_smp_call_function_queue(void) { } #endif diff --git a/kernel/smp.c b/kernel/smp.c index 01a7c1706a58..8e85f22ed538 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -96,7 +96,7 @@ static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data); static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue); -static void flush_smp_call_function_queue(bool warn_cpu_offline); +static void __flush_smp_call_function_queue(bool warn_cpu_offline); int smpcfd_prepare_cpu(unsigned int cpu) { @@ -141,7 +141,7 @@ int smpcfd_dying_cpu(unsigned int cpu) * ensure that the outgoing CPU doesn't go offline with work * still pending. */ - flush_smp_call_function_queue(false); + __flush_smp_call_function_queue(false); irq_work_run(); return 0; } @@ -541,11 +541,11 @@ void generic_smp_call_function_single_interrupt(void) { cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->gotipi, CFD_SEQ_NOCPU, smp_processor_id(), CFD_SEQ_GOTIPI); - flush_smp_call_function_queue(true); + __flush_smp_call_function_queue(true); } /** - * flush_smp_call_function_queue - Flush pending smp-call-function callbacks + * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks * * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an * offline CPU. Skip this check if set to 'false'. @@ -558,7 +558,7 @@ void generic_smp_call_function_single_interrupt(void) * Loop through the call_single_queue and run all the queued callbacks. * Must be called with interrupts disabled. */ -static void flush_smp_call_function_queue(bool warn_cpu_offline) +static void __flush_smp_call_function_queue(bool warn_cpu_offline) { call_single_data_t *csd, *csd_next; struct llist_node *entry, *prev; @@ -681,7 +681,20 @@ static void flush_smp_call_function_queue(bool warn_cpu_offline) smp_processor_id(), CFD_SEQ_HDLEND); } -void flush_smp_call_function_from_idle(void) + +/** + * flush_smp_call_function_queue - Flush pending smp-call-function callbacks + * from task context (idle, migration thread) + * + * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it + * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by + * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to + * handle queued SMP function calls before scheduling. + * + * The migration thread has to ensure that an eventually pending wakeup has + * been handled before it migrates a task. + */ +void flush_smp_call_function_queue(void) { unsigned long flags; @@ -691,7 +704,7 @@ void flush_smp_call_function_from_idle(void) cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->idle, CFD_SEQ_NOCPU, smp_processor_id(), CFD_SEQ_IDLE); local_irq_save(flags); - flush_smp_call_function_queue(true); + __flush_smp_call_function_queue(true); if (local_softirq_pending()) do_softirq();