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Tue, 14 Jun 2022 09:22:05 -0700 (PDT) Date: Tue, 14 Jun 2022 17:22:02 +0100 From: Mark Rutland To: Peter Zijlstra Cc: rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com, vgupta@kernel.org, linux@armlinux.org.uk, ulli.kroll@googlemail.com, linus.walleij@linaro.org, shawnguo@kernel.org, Sascha Hauer , kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, tony@atomide.com, khilman@kernel.org, catalin.marinas@arm.com, will@kernel.org, guoren@kernel.org, bcain@quicinc.com, chenhuacai@kernel.org, kernel@xen0n.name, geert@linux-m68k.org, sammy@sammy.net, monstr@monstr.eu, tsbogend@alpha.franken.de, dinguyen@kernel.org, jonas@southpole.se, stefan.kristiansson@saunalahti.fi, shorne@gmail.com, James.Bottomley@HansenPartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, acme@kernel.org, alexander.shishkin@linux.intel.com, jolsa@kernel.org, namhyung@kernel.org, jgross@suse.com, srivatsa@csail.mit.edu, amakhalov@vmware.com, pv-drivers@vmware.com, boris.ostrovsky@oracle.com, chris@zankel.net, jcmvbkbc@gmail.com, rafael@kernel.org, lenb@kernel.org, pavel@ucw.cz, gregkh@linuxfoundation.org, mturquette@baylibre.com, sboyd@kernel.org, daniel.lezcano@linaro.org, lpieralisi@kernel.org, sudeep.holla@arm.com, agross@kernel.org, bjorn.andersson@linaro.org, anup@brainfault.org, thierry.reding@gmail.com, jonathanh@nvidia.com, jacob.jun.pan@linux.intel.com, Arnd Bergmann , yury.norov@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk, rostedt@goodmis.org, pmladek@suse.com, senozhatsky@chromium.org, john.ogness@linutronix.de, paulmck@kernel.org, frederic@kernel.org, quic_neeraju@quicinc.com, josh@joshtriplett.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, jpoimboe@kernel.org, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-perf-users@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, linux-xtensa@linux-xtensa.org, linux-acpi@vger.kernel.org, linux-pm@vger.kernel.org, linux-clk@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-arch@vger.kernel.org, rcu@vger.kernel.org Subject: Re: [PATCH 20/36] arch/idle: Change arch_cpu_idle() IRQ behaviour Message-ID: References: <20220608142723.103523089@infradead.org> <20220608144517.188449351@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220608144517.188449351@infradead.org> Precedence: bulk List-ID: X-Mailing-List: linux-clk@vger.kernel.org On Wed, Jun 08, 2022 at 04:27:43PM +0200, Peter Zijlstra wrote: > 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) Nice! Acked-by: Mark Rutland [arm64] Mark. > --- > arch/alpha/kernel/process.c | 1 - > arch/arc/kernel/process.c | 3 +++ > arch/arm/kernel/process.c | 1 - > arch/arm/mach-gemini/board-dt.c | 3 ++- > arch/arm64/kernel/idle.c | 1 - > arch/csky/kernel/process.c | 1 - > arch/csky/kernel/smp.c | 2 +- > arch/hexagon/kernel/process.c | 1 - > arch/ia64/kernel/process.c | 1 + > arch/microblaze/kernel/process.c | 1 - > arch/mips/kernel/idle.c | 8 +++----- > arch/nios2/kernel/process.c | 1 - > arch/openrisc/kernel/process.c | 1 + > arch/parisc/kernel/process.c | 2 -- > arch/powerpc/kernel/idle.c | 5 ++--- > arch/riscv/kernel/process.c | 1 - > arch/s390/kernel/idle.c | 1 - > arch/sh/kernel/idle.c | 1 + > arch/sparc/kernel/leon_pmc.c | 4 ++++ > arch/sparc/kernel/process_32.c | 1 - > arch/sparc/kernel/process_64.c | 3 ++- > arch/um/kernel/process.c | 1 - > arch/x86/coco/tdx/tdx.c | 3 +++ > arch/x86/kernel/process.c | 15 ++++----------- > arch/xtensa/kernel/process.c | 1 + > kernel/sched/idle.c | 2 -- > 26 files changed, 28 insertions(+), 37 deletions(-) > > --- a/arch/alpha/kernel/process.c > +++ b/arch/alpha/kernel/process.c > @@ -57,7 +57,6 @@ EXPORT_SYMBOL(pm_power_off); > void arch_cpu_idle(void) > { > wtint(0); > - raw_local_irq_enable(); > } > > void arch_cpu_idle_dead(void) > --- a/arch/arc/kernel/process.c > +++ b/arch/arc/kernel/process.c > @@ -114,6 +114,8 @@ void arch_cpu_idle(void) > "sleep %0 \n" > : > :"I"(arg)); /* can't be "r" has to be embedded const */ > + > + raw_local_irq_disable(); > } > > #else /* ARC700 */ > @@ -122,6 +124,7 @@ void arch_cpu_idle(void) > { > /* sleep, but enable both set E1/E2 (levels of interrupts) before committing */ > __asm__ __volatile__("sleep 0x3 \n"); > + raw_local_irq_disable(); > } > > #endif > --- a/arch/arm/kernel/process.c > +++ b/arch/arm/kernel/process.c > @@ -78,7 +78,6 @@ void arch_cpu_idle(void) > arm_pm_idle(); > else > cpu_do_idle(); > - raw_local_irq_enable(); > } > > void arch_cpu_idle_prepare(void) > --- a/arch/arm/mach-gemini/board-dt.c > +++ b/arch/arm/mach-gemini/board-dt.c > @@ -42,8 +42,9 @@ static void gemini_idle(void) > */ > > /* FIXME: Enabling interrupts here is racy! */ > - local_irq_enable(); > + raw_local_irq_enable(); > cpu_do_idle(); > + raw_local_irq_disable(); > } > > static void __init gemini_init_machine(void) > --- a/arch/arm64/kernel/idle.c > +++ b/arch/arm64/kernel/idle.c > @@ -42,5 +42,4 @@ void noinstr arch_cpu_idle(void) > * tricks > */ > cpu_do_idle(); > - raw_local_irq_enable(); > } > --- a/arch/csky/kernel/process.c > +++ b/arch/csky/kernel/process.c > @@ -101,6 +101,5 @@ void arch_cpu_idle(void) > #ifdef CONFIG_CPU_PM_STOP > asm volatile("stop\n"); > #endif > - raw_local_irq_enable(); > } > #endif > --- a/arch/csky/kernel/smp.c > +++ b/arch/csky/kernel/smp.c > @@ -314,7 +314,7 @@ void arch_cpu_idle_dead(void) > while (!secondary_stack) > arch_cpu_idle(); > > - local_irq_disable(); > + raw_local_irq_disable(); > > asm volatile( > "mov sp, %0\n" > --- a/arch/hexagon/kernel/process.c > +++ b/arch/hexagon/kernel/process.c > @@ -44,7 +44,6 @@ void arch_cpu_idle(void) > { > __vmwait(); > /* interrupts wake us up, but irqs are still disabled */ > - raw_local_irq_enable(); > } > > /* > --- a/arch/ia64/kernel/process.c > +++ b/arch/ia64/kernel/process.c > @@ -241,6 +241,7 @@ void arch_cpu_idle(void) > (*mark_idle)(1); > > raw_safe_halt(); > + raw_local_irq_disable(); > > if (mark_idle) > (*mark_idle)(0); > --- a/arch/microblaze/kernel/process.c > +++ b/arch/microblaze/kernel/process.c > @@ -138,5 +138,4 @@ int dump_fpu(struct pt_regs *regs, elf_f > > void arch_cpu_idle(void) > { > - raw_local_irq_enable(); > } > --- a/arch/mips/kernel/idle.c > +++ b/arch/mips/kernel/idle.c > @@ -33,13 +33,13 @@ static void __cpuidle r3081_wait(void) > { > unsigned long cfg = read_c0_conf(); > write_c0_conf(cfg | R30XX_CONF_HALT); > - raw_local_irq_enable(); > } > > void __cpuidle r4k_wait(void) > { > raw_local_irq_enable(); > __r4k_wait(); > + raw_local_irq_disable(); > } > > /* > @@ -57,7 +57,6 @@ void __cpuidle r4k_wait_irqoff(void) > " .set arch=r4000 \n" > " wait \n" > " .set pop \n"); > - raw_local_irq_enable(); > } > > /* > @@ -77,7 +76,6 @@ static void __cpuidle rm7k_wait_irqoff(v > " wait \n" > " mtc0 $1, $12 # stalls until W stage \n" > " .set pop \n"); > - raw_local_irq_enable(); > } > > /* > @@ -103,6 +101,8 @@ static void __cpuidle au1k_wait(void) > " nop \n" > " .set pop \n" > : : "r" (au1k_wait), "r" (c0status)); > + > + raw_local_irq_disable(); > } > > static int __initdata nowait; > @@ -245,8 +245,6 @@ void arch_cpu_idle(void) > { > if (cpu_wait) > cpu_wait(); > - else > - raw_local_irq_enable(); > } > > #ifdef CONFIG_CPU_IDLE > --- a/arch/nios2/kernel/process.c > +++ b/arch/nios2/kernel/process.c > @@ -33,7 +33,6 @@ EXPORT_SYMBOL(pm_power_off); > > void arch_cpu_idle(void) > { > - raw_local_irq_enable(); > } > > /* > --- a/arch/openrisc/kernel/process.c > +++ b/arch/openrisc/kernel/process.c > @@ -102,6 +102,7 @@ void arch_cpu_idle(void) > raw_local_irq_enable(); > if (mfspr(SPR_UPR) & SPR_UPR_PMP) > mtspr(SPR_PMR, mfspr(SPR_PMR) | SPR_PMR_DME); > + raw_local_irq_disable(); > } > > void (*pm_power_off)(void) = NULL; > --- a/arch/parisc/kernel/process.c > +++ b/arch/parisc/kernel/process.c > @@ -187,8 +187,6 @@ void arch_cpu_idle_dead(void) > > void __cpuidle arch_cpu_idle(void) > { > - raw_local_irq_enable(); > - > /* nop on real hardware, qemu will idle sleep. */ > asm volatile("or %%r10,%%r10,%%r10\n":::); > } > --- a/arch/powerpc/kernel/idle.c > +++ b/arch/powerpc/kernel/idle.c > @@ -51,10 +51,9 @@ void arch_cpu_idle(void) > * Some power_save functions return with > * interrupts enabled, some don't. > */ > - if (irqs_disabled()) > - raw_local_irq_enable(); > + if (!irqs_disabled()) > + raw_local_irq_disable(); > } else { > - raw_local_irq_enable(); > /* > * Go into low thread priority and possibly > * low power mode. > --- a/arch/riscv/kernel/process.c > +++ b/arch/riscv/kernel/process.c > @@ -39,7 +39,6 @@ extern asmlinkage void ret_from_kernel_t > void arch_cpu_idle(void) > { > cpu_do_idle(); > - raw_local_irq_enable(); > } > > void __show_regs(struct pt_regs *regs) > --- a/arch/s390/kernel/idle.c > +++ b/arch/s390/kernel/idle.c > @@ -66,7 +66,6 @@ void arch_cpu_idle(void) > idle->idle_count++; > account_idle_time(cputime_to_nsecs(idle_time)); > raw_write_seqcount_end(&idle->seqcount); > - raw_local_irq_enable(); > } > > static ssize_t show_idle_count(struct device *dev, > --- a/arch/sh/kernel/idle.c > +++ b/arch/sh/kernel/idle.c > @@ -25,6 +25,7 @@ void default_idle(void) > raw_local_irq_enable(); > /* Isn't this racy ? */ > cpu_sleep(); > + raw_local_irq_disable(); > clear_bl_bit(); > } > > --- a/arch/sparc/kernel/leon_pmc.c > +++ b/arch/sparc/kernel/leon_pmc.c > @@ -57,6 +57,8 @@ static void pmc_leon_idle_fixup(void) > "lda [%0] %1, %%g0\n" > : > : "r"(address), "i"(ASI_LEON_BYPASS)); > + > + raw_local_irq_disable(); > } > > /* > @@ -70,6 +72,8 @@ static void pmc_leon_idle(void) > > /* For systems without power-down, this will be no-op */ > __asm__ __volatile__ ("wr %g0, %asr19\n\t"); > + > + raw_local_irq_disable(); > } > > /* Install LEON Power Down function */ > --- a/arch/sparc/kernel/process_32.c > +++ b/arch/sparc/kernel/process_32.c > @@ -71,7 +71,6 @@ void arch_cpu_idle(void) > { > if (sparc_idle) > (*sparc_idle)(); > - raw_local_irq_enable(); > } > > /* XXX cli/sti -> local_irq_xxx here, check this works once SMP is fixed. */ > --- a/arch/sparc/kernel/process_64.c > +++ b/arch/sparc/kernel/process_64.c > @@ -59,7 +59,6 @@ void arch_cpu_idle(void) > { > if (tlb_type != hypervisor) { > touch_nmi_watchdog(); > - raw_local_irq_enable(); > } else { > unsigned long pstate; > > @@ -90,6 +89,8 @@ void arch_cpu_idle(void) > "wrpr %0, %%g0, %%pstate" > : "=&r" (pstate) > : "i" (PSTATE_IE)); > + > + raw_local_irq_disable(); > } > } > > --- a/arch/um/kernel/process.c > +++ b/arch/um/kernel/process.c > @@ -216,7 +216,6 @@ void arch_cpu_idle(void) > { > cpu_tasks[current_thread_info()->cpu].pid = os_getpid(); > um_idle_sleep(); > - raw_local_irq_enable(); > } > > int __cant_sleep(void) { > --- a/arch/x86/coco/tdx/tdx.c > +++ b/arch/x86/coco/tdx/tdx.c > @@ -178,6 +178,9 @@ void __cpuidle tdx_safe_halt(void) > */ > if (__halt(irq_disabled, do_sti)) > WARN_ONCE(1, "HLT instruction emulation failed\n"); > + > + /* XXX I can't make sense of what @do_sti actually does */ > + raw_local_irq_disable(); > } > > static bool read_msr(struct pt_regs *regs) > --- a/arch/x86/kernel/process.c > +++ b/arch/x86/kernel/process.c > @@ -699,6 +699,7 @@ EXPORT_SYMBOL(boot_option_idle_override) > void __cpuidle default_idle(void) > { > raw_safe_halt(); > + raw_local_irq_disable(); > } > #if defined(CONFIG_APM_MODULE) || defined(CONFIG_HALTPOLL_CPUIDLE_MODULE) > EXPORT_SYMBOL(default_idle); > @@ -804,13 +805,7 @@ static void amd_e400_idle(void) > > default_idle(); > > - /* > - * The switch back from broadcast mode needs to be called with > - * interrupts disabled. > - */ > - raw_local_irq_disable(); > tick_broadcast_exit(); > - raw_local_irq_enable(); > } > > /* > @@ -849,12 +844,10 @@ static __cpuidle void mwait_idle(void) > } > > __monitor((void *)¤t_thread_info()->flags, 0, 0); > - if (!need_resched()) > + if (!need_resched()) { > __sti_mwait(0, 0); > - else > - raw_local_irq_enable(); > - } else { > - raw_local_irq_enable(); > + raw_local_irq_disable(); > + } > } > __current_clr_polling(); > } > --- a/arch/xtensa/kernel/process.c > +++ b/arch/xtensa/kernel/process.c > @@ -183,6 +183,7 @@ void coprocessor_flush_release_all(struc > void arch_cpu_idle(void) > { > platform_idle(); > + raw_local_irq_disable(); > } > > /* > --- a/kernel/sched/idle.c > +++ b/kernel/sched/idle.c > @@ -79,7 +79,6 @@ void __weak arch_cpu_idle_dead(void) { } > void __weak arch_cpu_idle(void) > { > cpu_idle_force_poll = 1; > - raw_local_irq_enable(); > } > > /** > @@ -96,7 +95,6 @@ void __cpuidle default_idle_call(void) > > cpuidle_rcu_enter(); > arch_cpu_idle(); > - raw_local_irq_disable(); > cpuidle_rcu_exit(); > > start_critical_timings(); > >