Re: [PATCH v3 1/1] powerpc: Enable dynamic preemption
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: 2025-01-30 14:54:11
Also in:
lkml
On 2025-01-06 10:49:19 [+0530], Shrikanth Hegde wrote:
quoted hunk ↗ jump to hunk
--- a/arch/powerpc/kernel/interrupt.c +++ b/arch/powerpc/kernel/interrupt.c@@ -25,6 +25,10 @@ unsigned long global_dbcr0[NR_CPUS]; #endif +#if defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) +DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); +#endif
I am uncertain here: Do you need to DEFINE it? It is set by the sched core which also defines it. It should be same thing after all, right?
quoted hunk ↗ jump to hunk
+ #ifdef CONFIG_PPC_BOOK3S_64 DEFINE_STATIC_KEY_FALSE(interrupt_exit_not_reentrant); static inline bool exit_must_hard_disable(void)@@ -396,7 +400,7 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs) /* Returning to a kernel context with local irqs enabled. */ WARN_ON_ONCE(!(regs->msr & MSR_EE)); again: - if (IS_ENABLED(CONFIG_PREEMPTION)) { + if (preempt_model_preemptible()) {
CONFIG_HAVE_PREEMPT_DYNAMIC_KEY is the only option, right? Wouldn't
| #DEFINE need_irq_preemption() \
| (static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched))
|
| if (need_irq_preemption()) {
be a bit smaller/ quicker? This could be a fast path ;)
quoted hunk ↗ jump to hunk
/* Return to preemptible kernel context */ if (unlikely(read_thread_flags() & _TIF_NEED_RESCHED)) { if (preempt_count() == 0)diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index edf5cabe5dfd..2556fa8ec019 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c@@ -266,7 +266,11 @@ static int __die(const char *str, struct pt_regs *regs, long err) printk("%s PAGE_SIZE=%luK%s%s%s%s%s%s %s\n", IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN) ? "LE" : "BE", PAGE_SIZE / 1024, get_mmu_str(), - IS_ENABLED(CONFIG_PREEMPT) ? " PREEMPT" : "", + preempt_model_none() ? "none" : + preempt_model_voluntary() ? "voluntary" : + preempt_model_full() ? "full" : + preempt_model_lazy() ? "lazy" : + "",
So intend to rework this part. I have patches stashed at https://git.kernel.org/pub/scm/linux/kernel/git/bigeasy/staging.git/log/?h=preemption_string which I didn't sent yet due to the merge window. Just a heads up ;)
IS_ENABLED(CONFIG_SMP) ? " SMP" : "",
IS_ENABLED(CONFIG_SMP) ? (" NR_CPUS=" __stringify(NR_CPUS)) : "",
debug_pagealloc_enabled() ? " DEBUG_PAGEALLOC" : "",Sebastian