| Message ID | 1399391708-13442-1-git-send-email-arunks.linux@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 05/06/2014 09:55 AM, arunks.linux@gmail.com wrote: > From: Arun KS <arun.linux@gmail.com> > > machine_shutdown() is a hook for kexec. Add a comment saying so, since > it isn't obvious from the function name. > > Halt, power-off, and restart have different requirements re: stopping > secondary CPUs than kexec has. The former simply require the secondary > CPUs to be quiesced somehow, whereas kexec requires them to be > completely non-operational, so that no matter where the kexec target > images are written in RAM, they won't influence operation of the > secondary CPUS,which could happen if the CPUs were still executing some > kind of pin loop. To this end, modify machine_halt, power_off, and > restart to call smp_send_stop() directly, rather than calling > machine_shutdown(). > > In machine_shutdown(), replace the call to smp_send_stop() with a call > to disable_nonboot_cpus(). This completely disables all but one CPU, > thus satisfying the kexec requirements a couple paragraphs above. > > Signed-off-by: Stephen Warren <swarren@nvidia.com> > Signed-off-by: Arun KS <getarunks@gmail.com> > Signed-off-by: Arun KS <arunks.linux@gmail.com> It's a bit odd to include my s-o-b here when I didn't actually write this particular patch. No doubt it's included because I wrote an identical patch for arch/arm/. Rather than including my s-o-b here, perhaps simply including the following paragraph in the commit decription would be better: This patch ports most of commit 19ab428f4b79 "ARM: 7759/1: decouple CPU offlining from reboot/shutdown" by Stephen Warren from arch/arm to arch/arm64. Or, I sometimes use the following tag instead of s-o-b: Based-on-work-by: Stephen Warren <swarren@nvidia.com> Including two s-o-b for yourself probably isn't necesary. Do you need to include an equivalent of the following from my original patch to arch/arm/? > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 239fa96c12bb..2651b1da1c56 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -2016,7 +2016,7 @@ config XIP_PHYS_ADDR > > config KEXEC > bool "Kexec system call (EXPERIMENTAL)" > - depends on (!SMP || HOTPLUG_CPU) > + depends on (!SMP || PM_SLEEP_SMP) > help > kexec is a system call that implements the ability to shutdown your > current kernel, and to start another kernel. It is like a reboot > diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c > index 8ef8c9337809..4fb074c446bf 100644 > --- a/arch/arm/kernel/machine_kexec.c > +++ b/arch/arm/kernel/machine_kexec.c > @@ -134,6 +134,10 @@ void machine_kexec(struct kimage *image) > unsigned long reboot_code_buffer_phys; > void *reboot_code_buffer; > > + if (num_online_cpus() > 1) { > + pr_err("kexec: error: multiple CPUs still online\n"); > + return; > + } > > page_list = image->head & PAGE_MASK; > > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c > index 550d63cef68e..5919eb451bb9 100644 > --- a/arch/arm/kernel/smp.c > +++ b/arch/arm/kernel/smp.c > @@ -651,17 +651,6 @@ void smp_send_reschedule(int cpu) > smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE); > } > > -#ifdef CONFIG_HOTPLUG_CPU > -static void smp_kill_cpus(cpumask_t *mask) > -{ > - unsigned int cpu; > - for_each_cpu(cpu, mask) > - platform_cpu_kill(cpu); > -} > -#else > -static void smp_kill_cpus(cpumask_t *mask) { } > -#endif > - > void smp_send_stop(void) > { > unsigned long timeout; > @@ -679,8 +668,6 @@ void smp_send_stop(void) > > if (num_online_cpus() > 1) > pr_warning("SMP: failed to stop secondary CPUs\n"); > - > - smp_kill_cpus(&mask); > } > > /*
Hi Stephen, On Tue, May 6, 2014 at 10:05 PM, Stephen Warren <swarren@wwwdotorg.org> wrote: > On 05/06/2014 09:55 AM, arunks.linux@gmail.com wrote: >> From: Arun KS <arun.linux@gmail.com> >> >> machine_shutdown() is a hook for kexec. Add a comment saying so, since >> it isn't obvious from the function name. >> >> Halt, power-off, and restart have different requirements re: stopping >> secondary CPUs than kexec has. The former simply require the secondary >> CPUs to be quiesced somehow, whereas kexec requires them to be >> completely non-operational, so that no matter where the kexec target >> images are written in RAM, they won't influence operation of the >> secondary CPUS,which could happen if the CPUs were still executing some >> kind of pin loop. To this end, modify machine_halt, power_off, and >> restart to call smp_send_stop() directly, rather than calling >> machine_shutdown(). >> >> In machine_shutdown(), replace the call to smp_send_stop() with a call >> to disable_nonboot_cpus(). This completely disables all but one CPU, >> thus satisfying the kexec requirements a couple paragraphs above. >> >> Signed-off-by: Stephen Warren <swarren@nvidia.com> >> Signed-off-by: Arun KS <getarunks@gmail.com> >> Signed-off-by: Arun KS <arunks.linux@gmail.com> > > It's a bit odd to include my s-o-b here when I didn't actually write > this particular patch. No doubt it's included because I wrote an > identical patch for arch/arm/. > > Rather than including my s-o-b here, perhaps simply including the > following paragraph in the commit decription would be better: > > This patch ports most of commit 19ab428f4b79 "ARM: 7759/1: decouple CPU > offlining from reboot/shutdown" by Stephen Warren from arch/arm to > arch/arm64. Okey. I ll re-spin this patch. > > Or, I sometimes use the following tag instead of s-o-b: > > Based-on-work-by: Stephen Warren <swarren@nvidia.com> > > Including two s-o-b for yourself probably isn't necesary. > > Do you need to include an equivalent of the following from my original > patch to arch/arm/? Rest of the things are already taken care in arm64. Thanks, Arun > >> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig >> index 239fa96c12bb..2651b1da1c56 100644 >> --- a/arch/arm/Kconfig >> +++ b/arch/arm/Kconfig >> @@ -2016,7 +2016,7 @@ config XIP_PHYS_ADDR >> >> config KEXEC >> bool "Kexec system call (EXPERIMENTAL)" >> - depends on (!SMP || HOTPLUG_CPU) >> + depends on (!SMP || PM_SLEEP_SMP) >> help >> kexec is a system call that implements the ability to shutdown your >> current kernel, and to start another kernel. It is like a reboot >> diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c >> index 8ef8c9337809..4fb074c446bf 100644 >> --- a/arch/arm/kernel/machine_kexec.c >> +++ b/arch/arm/kernel/machine_kexec.c >> @@ -134,6 +134,10 @@ void machine_kexec(struct kimage *image) >> unsigned long reboot_code_buffer_phys; >> void *reboot_code_buffer; >> >> + if (num_online_cpus() > 1) { >> + pr_err("kexec: error: multiple CPUs still online\n"); >> + return; >> + } >> >> page_list = image->head & PAGE_MASK; >> >> diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c >> index 550d63cef68e..5919eb451bb9 100644 >> --- a/arch/arm/kernel/smp.c >> +++ b/arch/arm/kernel/smp.c >> @@ -651,17 +651,6 @@ void smp_send_reschedule(int cpu) >> smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE); >> } >> >> -#ifdef CONFIG_HOTPLUG_CPU >> -static void smp_kill_cpus(cpumask_t *mask) >> -{ >> - unsigned int cpu; >> - for_each_cpu(cpu, mask) >> - platform_cpu_kill(cpu); >> -} >> -#else >> -static void smp_kill_cpus(cpumask_t *mask) { } >> -#endif >> - >> void smp_send_stop(void) >> { >> unsigned long timeout; >> @@ -679,8 +668,6 @@ void smp_send_stop(void) >> >> if (num_online_cpus() > 1) >> pr_warning("SMP: failed to stop secondary CPUs\n"); >> - >> - smp_kill_cpus(&mask); >> } >> >> /* >
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 6391485..2d43614 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -113,29 +113,58 @@ void arch_cpu_idle_dead(void) } #endif +/* + * Called by kexec, immediately prior to machine_kexec(). + * + * This must completely disable all secondary CPUs; simply causing those CPUs + * to execute e.g. a RAM-based pin loop is not sufficient. This allows the + * kexec'd kernel to use any and all RAM as it sees fit, without having to + * avoid any code or data used by any SW CPU pin loop. The CPU hotplug + * functionality embodied in disable_nonboot_cpus() to achieve this. + */ void machine_shutdown(void) { -#ifdef CONFIG_SMP - smp_send_stop(); -#endif + disable_nonboot_cpus(); } +/* + * Halting simply requires that the secondary CPUs stop performing any + * activity (executing tasks, handling interrupts). smp_send_stop() + * achieves this. + */ void machine_halt(void) { - machine_shutdown(); + smp_send_stop(); while (1); } +/* + * Power-off simply requires that the secondary CPUs stop performing any + * activity (executing tasks, handling interrupts). smp_send_stop() + * achieves this. When the system power is turned off, it will take all CPUs + * with it. + */ void machine_power_off(void) { - machine_shutdown(); + smp_send_stop(); if (pm_power_off) pm_power_off(); } +/* + * Restart requires that the secondary CPUs stop performing any activity + * while the primary CPU resets the system. Systems with a single CPU can + * use soft_restart() as their machine descriptor's .restart hook, since that + * will cause the only available CPU to reset. Systems with multiple CPUs must + * provide a HW restart implementation, to ensure that all CPUs reset at once. + * This is required so that any code running after reset on the primary CPU + * doesn't have to co-ordinate with other CPUs to ensure they aren't still + * executing pre-reset code, and using RAM that the primary CPU's code wishes + * to use. Implementing such co-ordination would be essentially impossible. + */ void machine_restart(char *cmd) { - machine_shutdown(); + smp_send_stop(); /* Disable interrupts first */ local_irq_disable();