Re: [PATCH 1/2] sched/idle: Fix arch_cpu_idle() vs tracing

Guenter Roeck
2020-11-30T21:00:03Z

On Fri, Nov 20, 2020 at 12:41:46PM +0100, Peter Zijlstra wrote:
> We call arch_cpu_idle() with RCU disabled, but then use
> local_irq_{en,dis}able(), which invokes tracing, which relies on RCU.
>
> Switch all arch_cpu_idle() implementations to use
> raw_local_irq_{en,dis}able() and carefully manage the
> lockdep,rcu,tracing state like we do in entry.
>
> (XXX: we really should change arch_cpu_idle() to not return with
> interrupts enabled)
>

Has this patch been tested on s390 ? Reason for asking is that it causes
all my s390 emulations to crash. Reverting it fixes the problem.

Guenter

> Reported-by: Mark Rutland <mark.rutland@arm.com>
> Reported-by: Sven Schnelle <svens@linux.ibm.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> arch/alpha/kernel/process.c | 2 +-
> arch/arm/kernel/process.c | 2 +-
> arch/arm64/kernel/process.c | 2 +-
> arch/csky/kernel/process.c | 2 +-
> arch/h8300/kernel/process.c | 2 +-
> arch/hexagon/kernel/process.c | 2 +-
> arch/ia64/kernel/process.c | 2 +-
> arch/microblaze/kernel/process.c | 2 +-
> arch/mips/kernel/idle.c | 12 ++++++------
> arch/nios2/kernel/process.c | 2 +-
> arch/openrisc/kernel/process.c | 2 +-
> arch/parisc/kernel/process.c | 2 +-
> arch/powerpc/kernel/idle.c | 4 ++--
> arch/riscv/kernel/process.c | 2 +-
> arch/s390/kernel/idle.c | 2 +-
> arch/sh/kernel/idle.c | 2 +-
> arch/sparc/kernel/leon_pmc.c | 4 ++--
> arch/sparc/kernel/process_32.c | 2 +-
> arch/sparc/kernel/process_64.c | 4 ++--
> arch/um/kernel/process.c | 2 +-
> arch/x86/include/asm/mwait.h | 2 --
> arch/x86/kernel/process.c | 12 +++++++-----
> kernel/sched/idle.c | 28 +++++++++++++++++++++++++++-
> 23 files changed, 62 insertions(+), 36 deletions(-)
>
> --- a/arch/alpha/kernel/process.c
> +++ b/arch/alpha/kernel/process.c
> @@ -57,7 +57,7 @@ EXPORT_SYMBOL(pm_power_off);
> void arch_cpu_idle(void)
> {
> wtint(0);
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> void arch_cpu_idle_dead(void)
> --- a/arch/arm/kernel/process.c
> +++ b/arch/arm/kernel/process.c
> @@ -71,7 +71,7 @@ void arch_cpu_idle(void)
> arm_pm_idle();
> else
> cpu_do_idle();
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> void arch_cpu_idle_prepare(void)
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -126,7 +126,7 @@ void arch_cpu_idle(void)
> * tricks
> */
> cpu_do_idle();
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> #ifdef CONFIG_HOTPLUG_CPU
> --- a/arch/csky/kernel/process.c
> +++ b/arch/csky/kernel/process.c
> @@ -102,6 +102,6 @@ void arch_cpu_idle(void)
> #ifdef CONFIG_CPU_PM_STOP
> asm volatile("stop\n");
> #endif
> - local_irq_enable();
> + raw_local_irq_enable();
> }
> #endif
> --- a/arch/h8300/kernel/process.c
> +++ b/arch/h8300/kernel/process.c
> @@ -57,7 +57,7 @@ asmlinkage void ret_from_kernel_thread(v
> */
> void arch_cpu_idle(void)
> {
> - local_irq_enable();
> + raw_local_irq_enable();
> __asm__("sleep");
> }
>
> --- a/arch/hexagon/kernel/process.c
> +++ b/arch/hexagon/kernel/process.c
> @@ -44,7 +44,7 @@ void arch_cpu_idle(void)
> {
> __vmwait();
> /* interrupts wake us up, but irqs are still disabled */
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> /*
> --- a/arch/ia64/kernel/process.c
> +++ b/arch/ia64/kernel/process.c
> @@ -239,7 +239,7 @@ void arch_cpu_idle(void)
> if (mark_idle)
> (*mark_idle)(1);
>
> - safe_halt();
> + raw_safe_halt();
>
> if (mark_idle)
> (*mark_idle)(0);
> --- a/arch/microblaze/kernel/process.c
> +++ b/arch/microblaze/kernel/process.c
> @@ -149,5 +149,5 @@ int dump_fpu(struct pt_regs *regs, elf_f
>
> void arch_cpu_idle(void)
> {
> - local_irq_enable();
> + raw_local_irq_enable();
> }
> --- a/arch/mips/kernel/idle.c
> +++ b/arch/mips/kernel/idle.c
> @@ -33,19 +33,19 @@ static void __cpuidle r3081_wait(void)
> {
> unsigned long cfg = read_c0_conf();
> write_c0_conf(cfg | R30XX_CONF_HALT);
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> static void __cpuidle r39xx_wait(void)
> {
> if (!need_resched())
> write_c0_conf(read_c0_conf() | TX39_CONF_HALT);
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> void __cpuidle r4k_wait(void)
> {
> - local_irq_enable();
> + raw_local_irq_enable();
> __r4k_wait();
> }
>
> @@ -64,7 +64,7 @@ void __cpuidle r4k_wait_irqoff(void)
> " .set arch=r4000 \n"
> " wait \n"
> " .set pop \n");
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> /*
> @@ -84,7 +84,7 @@ static void __cpuidle rm7k_wait_irqoff(v
> " wait \n"
> " mtc0 $1, $12 # stalls until W stage \n"
> " .set pop \n");
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> /*
> @@ -257,7 +257,7 @@ void arch_cpu_idle(void)
> if (cpu_wait)
> cpu_wait();
> else
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> #ifdef CONFIG_CPU_IDLE
> --- a/arch/nios2/kernel/process.c
> +++ b/arch/nios2/kernel/process.c
> @@ -33,7 +33,7 @@ EXPORT_SYMBOL(pm_power_off);
>
> void arch_cpu_idle(void)
> {
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> /*
> --- a/arch/openrisc/kernel/process.c
> +++ b/arch/openrisc/kernel/process.c
> @@ -79,7 +79,7 @@ void machine_power_off(void)
> */
> void arch_cpu_idle(void)
> {
> - local_irq_enable();
> + raw_local_irq_enable();
> if (mfspr(SPR_UPR) & SPR_UPR_PMP)
> mtspr(SPR_PMR, mfspr(SPR_PMR) | SPR_PMR_DME);
> }
> --- a/arch/parisc/kernel/process.c
> +++ b/arch/parisc/kernel/process.c
> @@ -169,7 +169,7 @@ void __cpuidle arch_cpu_idle_dead(void)
>
> void __cpuidle arch_cpu_idle(void)
> {
> - local_irq_enable();
> + 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
> @@ -52,9 +52,9 @@ void arch_cpu_idle(void)
> * interrupts enabled, some don't.
> */
> if (irqs_disabled())
> - local_irq_enable();
> + raw_local_irq_enable();
> } else {
> - local_irq_enable();
> + 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
> @@ -36,7 +36,7 @@ extern asmlinkage void ret_from_kernel_t
> void arch_cpu_idle(void)
> {
> wait_for_interrupt();
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> void show_regs(struct pt_regs *regs)
> --- a/arch/s390/kernel/idle.c
> +++ b/arch/s390/kernel/idle.c
> @@ -123,7 +123,7 @@ void arch_cpu_idle_enter(void)
> void arch_cpu_idle(void)
> {
> enabled_wait();
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> void arch_cpu_idle_exit(void)
> --- a/arch/sh/kernel/idle.c
> +++ b/arch/sh/kernel/idle.c
> @@ -22,7 +22,7 @@ static void (*sh_idle)(void);
> void default_idle(void)
> {
> set_bl_bit();
> - local_irq_enable();
> + raw_local_irq_enable();
> /* Isn't this racy ? */
> cpu_sleep();
> clear_bl_bit();
> --- a/arch/sparc/kernel/leon_pmc.c
> +++ b/arch/sparc/kernel/leon_pmc.c
> @@ -50,7 +50,7 @@ static void pmc_leon_idle_fixup(void)
> register unsigned int address = (unsigned int)leon3_irqctrl_regs;
>
> /* Interrupts need to be enabled to not hang the CPU */
> - local_irq_enable();
> + raw_local_irq_enable();
>
> __asm__ __volatile__ (
> "wr %%g0, %%asr19\n"
> @@ -66,7 +66,7 @@ static void pmc_leon_idle_fixup(void)
> static void pmc_leon_idle(void)
> {
> /* Interrupts need to be enabled to not hang the CPU */
> - local_irq_enable();
> + raw_local_irq_enable();
>
> /* For systems without power-down, this will be no-op */
> __asm__ __volatile__ ("wr %g0, %asr19\n\t");
> --- a/arch/sparc/kernel/process_32.c
> +++ b/arch/sparc/kernel/process_32.c
> @@ -74,7 +74,7 @@ void arch_cpu_idle(void)
> {
> if (sparc_idle)
> (*sparc_idle)();
> - local_irq_enable();
> + 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
> @@ -62,11 +62,11 @@ void arch_cpu_idle(void)
> {
> if (tlb_type != hypervisor) {
> touch_nmi_watchdog();
> - local_irq_enable();
> + raw_local_irq_enable();
> } else {
> unsigned long pstate;
>
> - local_irq_enable();
> + raw_local_irq_enable();
>
> /* The sun4v sleeping code requires that we have PSTATE.IE cleared over
> * the cpu sleep hypervisor call.
> --- a/arch/um/kernel/process.c
> +++ b/arch/um/kernel/process.c
> @@ -217,7 +217,7 @@ void arch_cpu_idle(void)
> {
> cpu_tasks[current_thread_info()->cpu].pid = os_getpid();
> um_idle_sleep();
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> int __cant_sleep(void) {
> --- a/arch/x86/include/asm/mwait.h
> +++ b/arch/x86/include/asm/mwait.h
> @@ -88,8 +88,6 @@ static inline void __mwaitx(unsigned lon
>
> static inline void __sti_mwait(unsigned long eax, unsigned long ecx)
> {
> - trace_hardirqs_on();
> -
> mds_idle_clear_cpu_buffers();
> /* "mwait %eax, %ecx;" */
> asm volatile("sti; .byte 0x0f, 0x01, 0xc9;"
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -685,7 +685,7 @@ void arch_cpu_idle(void)
> */
> void __cpuidle default_idle(void)
> {
> - safe_halt();
> + raw_safe_halt();
> }
> #if defined(CONFIG_APM_MODULE) || defined(CONFIG_HALTPOLL_CPUIDLE_MODULE)
> EXPORT_SYMBOL(default_idle);
> @@ -736,6 +736,8 @@ void stop_this_cpu(void *dummy)
> /*
> * AMD Erratum 400 aware idle routine. We handle it the same way as C3 power
> * states (local apic timer and TSC stop).
> + *
> + * XXX this function is completely buggered vs RCU and tracing.
> */
> static void amd_e400_idle(void)
> {
> @@ -757,9 +759,9 @@ static void amd_e400_idle(void)
> * The switch back from broadcast mode needs to be called with
> * interrupts disabled.
> */
> - local_irq_disable();
> + raw_local_irq_disable();
> tick_broadcast_exit();
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> /*
> @@ -801,9 +803,9 @@ static __cpuidle void mwait_idle(void)
> if (!need_resched())
> __sti_mwait(0, 0);
> else
> - local_irq_enable();
> + raw_local_irq_enable();
> } else {
> - local_irq_enable();
> + raw_local_irq_enable();
> }
> __current_clr_polling();
> }
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -78,7 +78,7 @@ void __weak arch_cpu_idle_dead(void) { }
> void __weak arch_cpu_idle(void)
> {
> cpu_idle_force_poll = 1;
> - local_irq_enable();
> + raw_local_irq_enable();
> }
>
> /**
> @@ -94,9 +94,35 @@ void __cpuidle default_idle_call(void)
>
> trace_cpu_idle(1, smp_processor_id());
> stop_critical_timings();
> +
> + /*
> + * arch_cpu_idle() is supposed to enable IRQs, however
> + * we can't do that because of RCU and tracing.
> + *
> + * Trace IRQs enable here, then switch off RCU, and have
> + * arch_cpu_idle() use raw_local_irq_enable(). Note that
> + * rcu_idle_enter() relies on lockdep IRQ state, so switch that
> + * last -- this is very similar to the entry code.
> + */
> + trace_hardirqs_on_prepare();
> + lockdep_hardirqs_on_prepare(_THIS_IP_);
> rcu_idle_enter();
> + lockdep_hardirqs_on(_THIS_IP_);
> +
> arch_cpu_idle();
> +
> + /*
> + * OK, so IRQs are enabled here, but RCU needs them disabled to
> + * turn itself back on.. funny thing is that disabling IRQs
> + * will cause tracing, which needs RCU. Jump through hoops to
> + * make it 'work'.
> + */
> + raw_local_irq_disable();
> + lockdep_hardirqs_off(_THIS_IP_);
> rcu_idle_exit();
> + lockdep_hardirqs_on(_THIS_IP_);
> + raw_local_irq_enable();
> +
> start_critical_timings();
> trace_cpu_idle(PWR_EVENT_EXIT, smp_processor_id());
> }
>
>