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[86.9.19.6]) by smtp.gmail.com with ESMTPSA id b5-v6sm3334071wrf.15.2018.10.30.04.46.05 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 30 Oct 2018 04:46:06 -0700 (PDT) Date: Tue, 30 Oct 2018 11:46:03 +0000 From: Daniel Thompson To: Douglas Anderson Cc: Jason Wessel , tglx@linutronix.de, mingo@kernel.org, gregkh@linuxfoundation.org, linux-arm-msm@vger.kernel.org, kgdb-bugreport@lists.sourceforge.net, kstewart@linuxfoundation.org, linux-mips@linux-mips.org, dalias@libc.org, linux-sh@vger.kernel.org, benh@kernel.crashing.org, will.deacon@arm.com, linux-kernel@vger.kernel.org, mhocko@suse.com, paulus@samba.org, hpa@zytor.com, sparclinux@vger.kernel.org, linux-hexagon@vger.kernel.org, sfr@canb.auug.org.au, ysato@users.sourceforge.jp, mpe@ellerman.id.au, x86@kernel.org, linux@armlinux.org.uk, mingo@redhat.com, catalin.marinas@arm.com, jhogan@kernel.org, linux-snps-arc@lists.infradead.org, ying.huang@intel.com, rppt@linux.vnet.ibm.com, bp@alien8.de, linux-arm-kernel@lists.infradead.org, christophe.leroy@c-s.fr, pombredanne@nexb.com, ralf@linux-mips.org, rkuo@codeaurora.org, paul.burton@mips.com, vgupta@synopsys.com, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, davem@davemloft.net Subject: Re: [PATCH 7/7] kgdb: Remove irq flags and local_irq_enable/disable from roundup Message-ID: <20181030114603.xdvyvayzw2an5c3q@holly.lan> References: <20181029180707.207546-1-dianders@chromium.org> <20181029180707.207546-8-dianders@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181029180707.207546-8-dianders@chromium.org> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 29, 2018 at 11:07:07AM -0700, Douglas Anderson wrote: > The function kgdb_roundup_cpus() was passed a parameter that was > documented as: > > > the flags that will be used when restoring the interrupts. There is > > local_irq_save() call before kgdb_roundup_cpus(). > > Nobody used those flags. Anyone who wanted to temporarily turn on > interrupts just did local_irq_enable() and local_irq_disable() without > looking at them. So we can definitely remove the flags. On the whole I'd rather that this change... > Speaking of calling local_irq_enable(), it seems like a bad idea and > it caused a nice splat on my system with lockdep turned on. > Specifically it hit: > DEBUG_LOCKS_WARN_ON(current->hardirq_context) ... and fixes for this this were in separate patches. They don't appear especially related. Daniel. > See the previous patch in this series ("smp: Don't yell about IRQs > disabled in kgdb_roundup_cpus()") for more details, but the last few > things on the stack were this on my arm64 board: > lockdep_hardirqs_on+0xf0/0x160 > trace_hardirqs_on+0x188/0x1ac > kgdb_roundup_cpus+0x14/0x3c > > As agrued in the the commit text of ("smp: Don't yell about IRQs > disabled in kgdb_roundup_cpus()"), it seems better to make > smp_call_function() lenient about kgdb than to locally turn on IRQs > here. Thus let's totally remove all the local_irq_enable() and > local_irq_disable() calls from all of the kgdb_roundup_cpus() calls. > > Signed-off-by: Douglas Anderson > --- > > arch/arc/kernel/kgdb.c | 4 +--- > arch/arm/kernel/kgdb.c | 4 +--- > arch/arm64/kernel/kgdb.c | 4 +--- > arch/hexagon/kernel/kgdb.c | 11 ++--------- > arch/mips/kernel/kgdb.c | 4 +--- > arch/powerpc/kernel/kgdb.c | 2 +- > arch/sh/kernel/kgdb.c | 4 +--- > arch/sparc/kernel/smp_64.c | 2 +- > arch/x86/kernel/kgdb.c | 9 ++------- > include/linux/kgdb.h | 9 ++------- > kernel/debug/debug_core.c | 2 +- > 11 files changed, 14 insertions(+), 41 deletions(-) > > diff --git a/arch/arc/kernel/kgdb.c b/arch/arc/kernel/kgdb.c > index 9a3c34af2ae8..d94d3cb7f9e8 100644 > --- a/arch/arc/kernel/kgdb.c > +++ b/arch/arc/kernel/kgdb.c > @@ -197,11 +197,9 @@ static void kgdb_call_nmi_hook(void *ignored) > kgdb_nmicallback(raw_smp_processor_id(), NULL); > } > > -void kgdb_roundup_cpus(unsigned long flags) > +void kgdb_roundup_cpus(void) > { > - local_irq_enable(); > smp_call_function(kgdb_call_nmi_hook, NULL, 0); > - local_irq_disable(); > } > > struct kgdb_arch arch_kgdb_ops = { > diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c > index caa0dbe3dc61..a80e9259f7e9 100644 > --- a/arch/arm/kernel/kgdb.c > +++ b/arch/arm/kernel/kgdb.c > @@ -175,11 +175,9 @@ static void kgdb_call_nmi_hook(void *ignored) > kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs()); > } > > -void kgdb_roundup_cpus(unsigned long flags) > +void kgdb_roundup_cpus(void) > { > - local_irq_enable(); > smp_call_function(kgdb_call_nmi_hook, NULL, 0); > - local_irq_disable(); > } > > static int __kgdb_notify(struct die_args *args, unsigned long cmd) > diff --git a/arch/arm64/kernel/kgdb.c b/arch/arm64/kernel/kgdb.c > index a20de58061a8..5d171c26788f 100644 > --- a/arch/arm64/kernel/kgdb.c > +++ b/arch/arm64/kernel/kgdb.c > @@ -289,11 +289,9 @@ static void kgdb_call_nmi_hook(void *ignored) > kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs()); > } > > -void kgdb_roundup_cpus(unsigned long flags) > +void kgdb_roundup_cpus(void) > { > - local_irq_enable(); > smp_call_function(kgdb_call_nmi_hook, NULL, 0); > - local_irq_disable(); > } > > static int __kgdb_notify(struct die_args *args, unsigned long cmd) > diff --git a/arch/hexagon/kernel/kgdb.c b/arch/hexagon/kernel/kgdb.c > index 16c24b22d0b2..30fbc491cf45 100644 > --- a/arch/hexagon/kernel/kgdb.c > +++ b/arch/hexagon/kernel/kgdb.c > @@ -119,17 +119,12 @@ void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc) > > /** > * kgdb_roundup_cpus - Get other CPUs into a holding pattern > - * @flags: Current IRQ state > * > * On SMP systems, we need to get the attention of the other CPUs > * and get them be in a known state. This should do what is needed > * to get the other CPUs to call kgdb_wait(). Note that on some arches, > * the NMI approach is not used for rounding up all the CPUs. For example, > - * in case of MIPS, smp_call_function() is used to roundup CPUs. In > - * this case, we have to make sure that interrupts are enabled before > - * calling smp_call_function(). The argument to this function is > - * the flags that will be used when restoring the interrupts. There is > - * local_irq_save() call before kgdb_roundup_cpus(). > + * in case of MIPS, smp_call_function() is used to roundup CPUs. > * > * On non-SMP systems, this is not called. > */ > @@ -139,11 +134,9 @@ static void hexagon_kgdb_nmi_hook(void *ignored) > kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs()); > } > > -void kgdb_roundup_cpus(unsigned long flags) > +void kgdb_roundup_cpus(void) > { > - local_irq_enable(); > smp_call_function(hexagon_kgdb_nmi_hook, NULL, 0); > - local_irq_disable(); > } > #endif > > diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c > index eb6c0d582626..6671a279966f 100644 > --- a/arch/mips/kernel/kgdb.c > +++ b/arch/mips/kernel/kgdb.c > @@ -219,11 +219,9 @@ static void kgdb_call_nmi_hook(void *ignored) > set_fs(old_fs); > } > > -void kgdb_roundup_cpus(unsigned long flags) > +void kgdb_roundup_cpus(void) > { > - local_irq_enable(); > smp_call_function(kgdb_call_nmi_hook, NULL, 0); > - local_irq_disable(); > } > > static int compute_signal(int tt) > diff --git a/arch/powerpc/kernel/kgdb.c b/arch/powerpc/kernel/kgdb.c > index 59c578f865aa..b0e804844be0 100644 > --- a/arch/powerpc/kernel/kgdb.c > +++ b/arch/powerpc/kernel/kgdb.c > @@ -124,7 +124,7 @@ static int kgdb_call_nmi_hook(struct pt_regs *regs) > } > > #ifdef CONFIG_SMP > -void kgdb_roundup_cpus(unsigned long flags) > +void kgdb_roundup_cpus(void) > { > smp_send_debugger_break(); > } > diff --git a/arch/sh/kernel/kgdb.c b/arch/sh/kernel/kgdb.c > index 4f04c6638a4d..86b3ea927e42 100644 > --- a/arch/sh/kernel/kgdb.c > +++ b/arch/sh/kernel/kgdb.c > @@ -319,11 +319,9 @@ static void kgdb_call_nmi_hook(void *ignored) > kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs()); > } > > -void kgdb_roundup_cpus(unsigned long flags) > +void kgdb_roundup_cpus(void) > { > - local_irq_enable(); > smp_call_function(kgdb_call_nmi_hook, NULL, 0); > - local_irq_disable(); > } > > static int __kgdb_notify(struct die_args *args, unsigned long cmd) > diff --git a/arch/sparc/kernel/smp_64.c b/arch/sparc/kernel/smp_64.c > index 4792e08ad36b..f45d876983f1 100644 > --- a/arch/sparc/kernel/smp_64.c > +++ b/arch/sparc/kernel/smp_64.c > @@ -1014,7 +1014,7 @@ void flush_dcache_page_all(struct mm_struct *mm, struct page *page) > } > > #ifdef CONFIG_KGDB > -void kgdb_roundup_cpus(unsigned long flags) > +void kgdb_roundup_cpus(void) > { > smp_cross_call(&xcall_kgdb_capture, 0, 0, 0); > } > diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c > index 8e36f249646e..ac6291a4178d 100644 > --- a/arch/x86/kernel/kgdb.c > +++ b/arch/x86/kernel/kgdb.c > @@ -422,21 +422,16 @@ static void kgdb_disable_hw_debug(struct pt_regs *regs) > #ifdef CONFIG_SMP > /** > * kgdb_roundup_cpus - Get other CPUs into a holding pattern > - * @flags: Current IRQ state > * > * On SMP systems, we need to get the attention of the other CPUs > * and get them be in a known state. This should do what is needed > * to get the other CPUs to call kgdb_wait(). Note that on some arches, > * the NMI approach is not used for rounding up all the CPUs. For example, > - * in case of MIPS, smp_call_function() is used to roundup CPUs. In > - * this case, we have to make sure that interrupts are enabled before > - * calling smp_call_function(). The argument to this function is > - * the flags that will be used when restoring the interrupts. There is > - * local_irq_save() call before kgdb_roundup_cpus(). > + * in case of MIPS, smp_call_function() is used to roundup CPUs. > * > * On non-SMP systems, this is not called. > */ > -void kgdb_roundup_cpus(unsigned long flags) > +void kgdb_roundup_cpus(void) > { > apic->send_IPI_allbutself(APIC_DM_NMI); > } > diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h > index e465bb15912d..05e5b2eb0d32 100644 > --- a/include/linux/kgdb.h > +++ b/include/linux/kgdb.h > @@ -178,21 +178,16 @@ kgdb_arch_handle_exception(int vector, int signo, int err_code, > > /** > * kgdb_roundup_cpus - Get other CPUs into a holding pattern > - * @flags: Current IRQ state > * > * On SMP systems, we need to get the attention of the other CPUs > * and get them into a known state. This should do what is needed > * to get the other CPUs to call kgdb_wait(). Note that on some arches, > * the NMI approach is not used for rounding up all the CPUs. For example, > - * in case of MIPS, smp_call_function() is used to roundup CPUs. In > - * this case, we have to make sure that interrupts are enabled before > - * calling smp_call_function(). The argument to this function is > - * the flags that will be used when restoring the interrupts. There is > - * local_irq_save() call before kgdb_roundup_cpus(). > + * in case of MIPS, smp_call_function() is used to roundup CPUs. > * > * On non-SMP systems, this is not called. > */ > -extern void kgdb_roundup_cpus(unsigned long flags); > +extern void kgdb_roundup_cpus(void); > > /** > * kgdb_arch_set_pc - Generic call back to the program counter > diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c > index 65c0f1363788..f3cadda45f07 100644 > --- a/kernel/debug/debug_core.c > +++ b/kernel/debug/debug_core.c > @@ -593,7 +593,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs, > > /* Signal the other CPUs to enter kgdb_wait() */ > else if ((!kgdb_single_step) && kgdb_do_roundup) > - kgdb_roundup_cpus(flags); > + kgdb_roundup_cpus(); > #endif > > /* > -- > 2.19.1.568.g152ad8e336-goog >