From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 928F7C41513 for ; Fri, 4 Aug 2023 07:50:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233169AbjHDHuj (ORCPT ); Fri, 4 Aug 2023 03:50:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42738 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229882AbjHDHuh (ORCPT ); Fri, 4 Aug 2023 03:50:37 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [IPv6:2001:67c:2178:6::1c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4DAFD421E; Fri, 4 Aug 2023 00:50:35 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 186B221866; Fri, 4 Aug 2023 07:50:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1691135433; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=TWMlbWBIl4ADD8tbSvSsJ/OHirnRKZ3VuNE+1LXNH6g=; b=eTMPwB7TVSeyowJOlx6AWLStHvNNNeX2IbpExdSA9nuPuJkwgAutxAWnQxtBnjM61In5Lk MaIc1IVCxhaNTo17Gnt4Sw9kixBuYpsfxhkT1wQYdfGsLtqOkn8i3K+zwh8QSjrfE43b7G xk5t03O1wqVhCM/AGzhjxUdgNnIWUcM= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id E06CE13904; Fri, 4 Aug 2023 07:50:32 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 2NQ0NsitzGQ5ZQAAMHmgww (envelope-from ); Fri, 04 Aug 2023 07:50:32 +0000 Date: Fri, 4 Aug 2023 09:50:32 +0200 From: Michal Hocko To: Douglas Anderson Cc: Andrew Morton , Petr Mladek , Arnd Bergmann , Borislav Petkov , Christophe Leroy , "Darrick J. Wong" , Dave Hansen , "David S. Miller" , Gaosheng Cui , "Gautham R. Shenoy" , Greg Kroah-Hartman , "Guilherme G. Piccoli" , Guo Ren , "H. Peter Anvin" , Huacai Chen , Ingo Molnar , "Jason A. Donenfeld" , Jianmin Lv , Jinyang He , Josh Poimboeuf , Kees Cook , Lecopzer Chen , Marc Zyngier , Mark Rutland , Michael Ellerman , Nicholas Piggin , "Paul E. McKenney" , Peter Zijlstra , Pingfan Liu , Qing Zhang , "Rafael J. Wysocki" , Russell King , Stephen Rothwell , Thomas Bogendoerfer , Thomas Gleixner , Tom Rix , Ulf Hansson , Valentin Schneider , WANG Xuerui , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, loongarch@lists.linux.dev, sparclinux@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v3 1/2] nmi_backtrace: Allow excluding an arbitrary CPU Message-ID: References: <20230803160649.v3.1.Ia35521b91fc781368945161d7b28538f9996c182@changeid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230803160649.v3.1.Ia35521b91fc781368945161d7b28538f9996c182@changeid> Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Thu 03-08-23 16:07:57, Douglas Anderson wrote: > The APIs that allow backtracing across CPUs have always had a way to > exclude the current CPU. This convenience means callers didn't need to > find a place to allocate a CPU mask just to handle the common case. > > Let's extend the API to take a CPU ID to exclude instead of just a > boolean. This isn't any more complex for the API to handle and allows > the hardlockup detector to exclude a different CPU (the one it already > did a trace for) without needing to find space for a CPU mask. > > Arguably, this new API also encourages safer behavior. Specifically if > the caller wants to avoid tracing the current CPU (maybe because they > already traced the current CPU) this makes it more obvious to the > caller that they need to make sure that the current CPU ID can't > change. Yes, this looks like the best way forward. It would have been slightly safer to modify arch_trigger_cpumask_backtrace by switching arguments so that some leftovers are captured easier. You also have this leftover diff --git a/include/linux/nmi.h b/include/linux/nmi.h index 00982b133dc1..9f1743ee2b28 100644 --- a/include/linux/nmi.h +++ b/include/linux/nmi.h @@ -190,10 +190,6 @@ static inline bool trigger_all_cpu_backtrace(void) { return false; } -static inline bool trigger_allbutself_cpu_backtrace(void) -{ - return false; -} static inline bool trigger_cpumask_backtrace(struct cpumask *mask) { return false; > Signed-off-by: Douglas Anderson Anyway Acked-by: Michal Hocko > --- > > Changes in v3: > - ("nmi_backtrace: Allow excluding an arbitrary CPU") new for v3. > > arch/arm/include/asm/irq.h | 2 +- > arch/arm/kernel/smp.c | 4 ++-- > arch/loongarch/include/asm/irq.h | 2 +- > arch/loongarch/kernel/process.c | 4 ++-- > arch/mips/include/asm/irq.h | 2 +- > arch/mips/kernel/process.c | 4 ++-- > arch/powerpc/include/asm/irq.h | 2 +- > arch/powerpc/kernel/stacktrace.c | 4 ++-- > arch/powerpc/kernel/watchdog.c | 4 ++-- > arch/sparc/include/asm/irq_64.h | 2 +- > arch/sparc/kernel/process_64.c | 6 +++--- > arch/x86/include/asm/irq.h | 2 +- > arch/x86/kernel/apic/hw_nmi.c | 4 ++-- > include/linux/nmi.h | 12 ++++++------ > kernel/watchdog.c | 2 +- > lib/nmi_backtrace.c | 6 +++--- > 16 files changed, 31 insertions(+), 31 deletions(-) > > diff --git a/arch/arm/include/asm/irq.h b/arch/arm/include/asm/irq.h > index 18605f1b3580..26c1d2ced4ce 100644 > --- a/arch/arm/include/asm/irq.h > +++ b/arch/arm/include/asm/irq.h > @@ -32,7 +32,7 @@ void handle_IRQ(unsigned int, struct pt_regs *); > #include > > extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask, > - bool exclude_self); > + int exclude_cpu); > #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace > #endif > > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c > index 6756203e45f3..3431c0553f45 100644 > --- a/arch/arm/kernel/smp.c > +++ b/arch/arm/kernel/smp.c > @@ -846,7 +846,7 @@ static void raise_nmi(cpumask_t *mask) > __ipi_send_mask(ipi_desc[IPI_CPU_BACKTRACE], mask); > } > > -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) > +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) > { > - nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_nmi); > + nmi_trigger_cpumask_backtrace(mask, exclude_cpu, raise_nmi); > } > diff --git a/arch/loongarch/include/asm/irq.h b/arch/loongarch/include/asm/irq.h > index a115e8999c69..218b4da0ea90 100644 > --- a/arch/loongarch/include/asm/irq.h > +++ b/arch/loongarch/include/asm/irq.h > @@ -40,7 +40,7 @@ void spurious_interrupt(void); > #define NR_IRQS_LEGACY 16 > > #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace > -void arch_trigger_cpumask_backtrace(const struct cpumask *mask, bool exclude_self); > +void arch_trigger_cpumask_backtrace(const struct cpumask *mask, int exclude_cpu); > > #define MAX_IO_PICS 2 > #define NR_IRQS (64 + (256 * MAX_IO_PICS)) > diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c > index 2e04eb07abb6..778e8d09953e 100644 > --- a/arch/loongarch/kernel/process.c > +++ b/arch/loongarch/kernel/process.c > @@ -345,9 +345,9 @@ static void raise_backtrace(cpumask_t *mask) > } > } > > -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) > +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) > { > - nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace); > + nmi_trigger_cpumask_backtrace(mask, exclude_cpu, raise_backtrace); > } > > #ifdef CONFIG_64BIT > diff --git a/arch/mips/include/asm/irq.h b/arch/mips/include/asm/irq.h > index 75abfa834ab7..3a848e7e69f7 100644 > --- a/arch/mips/include/asm/irq.h > +++ b/arch/mips/include/asm/irq.h > @@ -77,7 +77,7 @@ extern int cp0_fdc_irq; > extern int get_c0_fdc_int(void); > > void arch_trigger_cpumask_backtrace(const struct cpumask *mask, > - bool exclude_self); > + int exclude_cpu); > #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace > > #endif /* _ASM_IRQ_H */ > diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c > index a3225912c862..5387ed0a5186 100644 > --- a/arch/mips/kernel/process.c > +++ b/arch/mips/kernel/process.c > @@ -750,9 +750,9 @@ static void raise_backtrace(cpumask_t *mask) > } > } > > -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) > +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) > { > - nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace); > + nmi_trigger_cpumask_backtrace(mask, exclude_cpu, raise_backtrace); > } > > int mips_get_process_fp_mode(struct task_struct *task) > diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h > index f257cacb49a9..ba1a5974e714 100644 > --- a/arch/powerpc/include/asm/irq.h > +++ b/arch/powerpc/include/asm/irq.h > @@ -55,7 +55,7 @@ int irq_choose_cpu(const struct cpumask *mask); > > #if defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) > extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask, > - bool exclude_self); > + int exclude_cpu); > #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace > #endif > > diff --git a/arch/powerpc/kernel/stacktrace.c b/arch/powerpc/kernel/stacktrace.c > index 5de8597eaab8..b15f15dcacb5 100644 > --- a/arch/powerpc/kernel/stacktrace.c > +++ b/arch/powerpc/kernel/stacktrace.c > @@ -221,8 +221,8 @@ static void raise_backtrace_ipi(cpumask_t *mask) > } > } > > -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) > +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) > { > - nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi); > + nmi_trigger_cpumask_backtrace(mask, exclude_cpu, raise_backtrace_ipi); > } > #endif /* defined(CONFIG_PPC_BOOK3S_64) && defined(CONFIG_NMI_IPI) */ > diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c > index edb2dd1f53eb..8c464a5d8246 100644 > --- a/arch/powerpc/kernel/watchdog.c > +++ b/arch/powerpc/kernel/watchdog.c > @@ -245,7 +245,7 @@ static void watchdog_smp_panic(int cpu) > __cpumask_clear_cpu(c, &wd_smp_cpus_ipi); > } > } else { > - trigger_allbutself_cpu_backtrace(); > + trigger_allbutcpu_cpu_backtrace(cpu); > cpumask_clear(&wd_smp_cpus_ipi); > } > > @@ -416,7 +416,7 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt) > xchg(&__wd_nmi_output, 1); // see wd_lockup_ipi > > if (sysctl_hardlockup_all_cpu_backtrace) > - trigger_allbutself_cpu_backtrace(); > + trigger_allbutcpu_cpu_backtrace(cpu); > > if (hardlockup_panic) > nmi_panic(regs, "Hard LOCKUP"); > diff --git a/arch/sparc/include/asm/irq_64.h b/arch/sparc/include/asm/irq_64.h > index b436029f1ced..8c4c0c87f998 100644 > --- a/arch/sparc/include/asm/irq_64.h > +++ b/arch/sparc/include/asm/irq_64.h > @@ -87,7 +87,7 @@ static inline unsigned long get_softint(void) > } > > void arch_trigger_cpumask_backtrace(const struct cpumask *mask, > - bool exclude_self); > + int exclude_cpu); > #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace > > extern void *hardirq_stack[NR_CPUS]; > diff --git a/arch/sparc/kernel/process_64.c b/arch/sparc/kernel/process_64.c > index b51d8fb0ecdc..1ea3f37fa985 100644 > --- a/arch/sparc/kernel/process_64.c > +++ b/arch/sparc/kernel/process_64.c > @@ -236,7 +236,7 @@ static void __global_reg_poll(struct global_reg_snapshot *gp) > } > } > > -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) > +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) > { > struct thread_info *tp = current_thread_info(); > struct pt_regs *regs = get_irq_regs(); > @@ -252,7 +252,7 @@ void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) > > memset(global_cpu_snapshot, 0, sizeof(global_cpu_snapshot)); > > - if (cpumask_test_cpu(this_cpu, mask) && !exclude_self) > + if (cpumask_test_cpu(this_cpu, mask) && this_cpu != exclude_cpu) > __global_reg_self(tp, regs, this_cpu); > > smp_fetch_global_regs(); > @@ -260,7 +260,7 @@ void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) > for_each_cpu(cpu, mask) { > struct global_reg_snapshot *gp; > > - if (exclude_self && cpu == this_cpu) > + if (cpu == exclude_cpu) > continue; > > gp = &global_cpu_snapshot[cpu].reg; > diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h > index 29e083b92813..836c170d3087 100644 > --- a/arch/x86/include/asm/irq.h > +++ b/arch/x86/include/asm/irq.h > @@ -42,7 +42,7 @@ extern void init_ISA_irqs(void); > > #ifdef CONFIG_X86_LOCAL_APIC > void arch_trigger_cpumask_backtrace(const struct cpumask *mask, > - bool exclude_self); > + int exclude_cpu); > > #define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace > #endif > diff --git a/arch/x86/kernel/apic/hw_nmi.c b/arch/x86/kernel/apic/hw_nmi.c > index 34a992e275ef..d6e01f924299 100644 > --- a/arch/x86/kernel/apic/hw_nmi.c > +++ b/arch/x86/kernel/apic/hw_nmi.c > @@ -34,9 +34,9 @@ static void nmi_raise_cpu_backtrace(cpumask_t *mask) > apic->send_IPI_mask(mask, NMI_VECTOR); > } > > -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) > +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, int exclude_cpu) > { > - nmi_trigger_cpumask_backtrace(mask, exclude_self, > + nmi_trigger_cpumask_backtrace(mask, exclude_cpu, > nmi_raise_cpu_backtrace); > } > > diff --git a/include/linux/nmi.h b/include/linux/nmi.h > index e3e6a64b98e0..00982b133dc1 100644 > --- a/include/linux/nmi.h > +++ b/include/linux/nmi.h > @@ -157,31 +157,31 @@ static inline void touch_nmi_watchdog(void) > #ifdef arch_trigger_cpumask_backtrace > static inline bool trigger_all_cpu_backtrace(void) > { > - arch_trigger_cpumask_backtrace(cpu_online_mask, false); > + arch_trigger_cpumask_backtrace(cpu_online_mask, -1); > return true; > } > > -static inline bool trigger_allbutself_cpu_backtrace(void) > +static inline bool trigger_allbutcpu_cpu_backtrace(int exclude_cpu) > { > - arch_trigger_cpumask_backtrace(cpu_online_mask, true); > + arch_trigger_cpumask_backtrace(cpu_online_mask, exclude_cpu); > return true; > } > > static inline bool trigger_cpumask_backtrace(struct cpumask *mask) > { > - arch_trigger_cpumask_backtrace(mask, false); > + arch_trigger_cpumask_backtrace(mask, -1); > return true; > } > > static inline bool trigger_single_cpu_backtrace(int cpu) > { > - arch_trigger_cpumask_backtrace(cpumask_of(cpu), false); > + arch_trigger_cpumask_backtrace(cpumask_of(cpu), -1); > return true; > } > > /* generic implementation */ > void nmi_trigger_cpumask_backtrace(const cpumask_t *mask, > - bool exclude_self, > + int exclude_cpu, > void (*raise)(cpumask_t *mask)); > bool nmi_cpu_backtrace(struct pt_regs *regs); > > diff --git a/kernel/watchdog.c b/kernel/watchdog.c > index be38276a365f..085d7a78f62f 100644 > --- a/kernel/watchdog.c > +++ b/kernel/watchdog.c > @@ -523,7 +523,7 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer) > dump_stack(); > > if (softlockup_all_cpu_backtrace) { > - trigger_allbutself_cpu_backtrace(); > + trigger_allbutcpu_cpu_backtrace(smp_processor_id()); > clear_bit_unlock(0, &soft_lockup_nmi_warn); > } > > diff --git a/lib/nmi_backtrace.c b/lib/nmi_backtrace.c > index 5274bbb026d7..33c154264bfe 100644 > --- a/lib/nmi_backtrace.c > +++ b/lib/nmi_backtrace.c > @@ -34,7 +34,7 @@ static unsigned long backtrace_flag; > * they are passed being updated as a side effect of this call. > */ > void nmi_trigger_cpumask_backtrace(const cpumask_t *mask, > - bool exclude_self, > + int exclude_cpu, > void (*raise)(cpumask_t *mask)) > { > int i, this_cpu = get_cpu(); > @@ -49,8 +49,8 @@ void nmi_trigger_cpumask_backtrace(const cpumask_t *mask, > } > > cpumask_copy(to_cpumask(backtrace_mask), mask); > - if (exclude_self) > - cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask)); > + if (exclude_cpu != -1) > + cpumask_clear_cpu(exclude_cpu, to_cpumask(backtrace_mask)); > > /* > * Don't try to send an NMI to this cpu; it may work on some > -- > 2.41.0.585.gd2178a4bd4-goog -- Michal Hocko SUSE Labs