| Message ID | 20181029180707.207546-8-dianders@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | None | expand |
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 <dianders@chromium.org> > --- > > 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 >
Hi, On Tue, Oct 30, 2018 at 4:46 AM Daniel Thompson <daniel.thompson@linaro.org> wrote: > > 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. Agreed that this is cleaner. Done for v2. -Doug
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 /*