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Date: Mon, 15 Apr 2013 10:18:31 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Robin Holt <holt@....com>, Ingo Molnar <mingo@...hat.com>,
Russ Anderson <rja@....com>
CC: Shawn Guo <shawn.guo@...aro.org>, Oleg Nesterov <oleg@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Lai Jiangshan <laijs@...fujitsu.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Michel Lespinasse <walken@...gle.com>,
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
Paul Mackerras <paulus@...ba.org>,
Peter Zijlstra <peterz@...radead.org>,
"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
Tejun Heo <tj@...nel.org>,
the arch/x86 maintainers <x86@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [Patch -v3 4/4] Make reboot_cpuid a kernel parameter.
Um... doesn't this break anyone who currently depends on this?
Robin Holt <holt@....com> wrote:
>
>Moving the reboot=s<##> parameter for x86 to a kernel parameter
>proper. I did not find any other arch that was specifying the
>reboot cpu.
>
>Signed-off-by: Robin Holt <holt@....com>
>To: Ingo Molnar <mingo@...hat.com>
>To: Russ Anderson <rja@....com>
>Cc: Shawn Guo <shawn.guo@...aro.org>
>Cc: Oleg Nesterov <oleg@...hat.com>
>Cc: Andrew Morton <akpm@...ux-foundation.org>
>Cc: "H. Peter Anvin" <hpa@...or.com>
>Cc: Lai Jiangshan <laijs@...fujitsu.com>
>Cc: Linus Torvalds <torvalds@...ux-foundation.org>
>Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
>Cc: Michel Lespinasse <walken@...gle.com>
>Cc: Oleg Nesterov <oleg@...hat.com>
>Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
>Cc: Paul Mackerras <paulus@...ba.org>
>Cc: Peter Zijlstra <peterz@...radead.org>
>Cc: Robin Holt <holt@....com>
>Cc: "rusty@...tcorp.com.au" <rusty@...tcorp.com.au>
>Cc: Tejun Heo <tj@...nel.org>
>Cc: the arch/x86 maintainers <x86@...nel.org>
>Cc: Thomas Gleixner <tglx@...utronix.de>
>---
> Documentation/kernel-parameters.txt | 2 ++
>arch/x86/kernel/reboot.c | 44
>++++---------------------------------
> kernel/reboot.c | 8 ++++++-
> 3 files changed, 13 insertions(+), 41 deletions(-)
>
>diff --git a/Documentation/kernel-parameters.txt
>b/Documentation/kernel-parameters.txt
>index 4609e81..11ebb48 100644
>--- a/Documentation/kernel-parameters.txt
>+++ b/Documentation/kernel-parameters.txt
>@@ -2597,6 +2597,8 @@ bytes respectively. Such letter suffixes can also
>be entirely omitted.
> Format: <reboot_mode>[,<reboot_mode2>[,...]]
> See arch/*/kernel/reboot.c or arch/*/kernel/process.c
>
>+ reboot_cpuid= [KNL] cpuid to use for reboot/halt, etc operations.
>+
> relax_domain_level=
> [KNL, SMP] Set scheduler's default relax_domain_level.
> See Documentation/cgroups/cpusets.txt.
>diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
>index 76fa1e9..39af130 100644
>--- a/arch/x86/kernel/reboot.c
>+++ b/arch/x86/kernel/reboot.c
>@@ -49,10 +49,6 @@ int reboot_force;
> */
> static int reboot_default = 1;
>
>-#ifdef CONFIG_SMP
>-static int reboot_cpu = -1;
>-#endif
>-
> /*
> * This is set if we need to go through the 'emergency' path.
> * When machine_emergency_restart() is called, we may be on
>@@ -64,11 +60,10 @@ static int reboot_emergency;
> bool port_cf9_safe = false;
>
> /*
>- * reboot=b[ios] | s[mp] | t[riple] | k[bd] | e[fi] [, [w]arm |
>[c]old] | p[ci]
>+ * reboot=b[ios] | t[riple] | k[bd] | e[fi] [, [w]arm | [c]old] |
>p[ci]
> * warm Don't set the cold reboot flag
> * cold Set the cold reboot flag
> * bios Reboot by jumping through the BIOS
>- * smp Reboot by executing reset on BSP or other CPU
> * triple Force a triple fault (init)
> * kbd Use the keyboard controller. cold reset (default)
> * acpi Use the RESET_REG in the FADT
>@@ -95,21 +90,6 @@ static int __init reboot_setup(char *str)
> reboot_mode = 0;
> break;
>
>-#ifdef CONFIG_SMP
>- case 's':
>- if (isdigit(*(str+1))) {
>- reboot_cpu = (int) (*(str+1) - '0');
>- if (isdigit(*(str+2)))
>- reboot_cpu = reboot_cpu*10 + (int)(*(str+2) - '0');
>- }
>- /*
>- * We will leave sorting out the final value
>- * when we are ready to reboot, since we might not
>- * have detected BSP APIC ID or smp_num_cpu
>- */
>- break;
>-#endif /* CONFIG_SMP */
>-
> case 'b':
> case 'a':
> case 'k':
>@@ -614,26 +594,10 @@ void native_machine_shutdown(void)
> {
> /* Stop the cpus and apics */
> #ifdef CONFIG_SMP
>-
>- /* The boot cpu is always logical cpu 0 */
>- int reboot_cpu_id = 0;
>-
>- /* See if there has been given a command line override */
>- if ((reboot_cpu != -1) && (reboot_cpu < nr_cpu_ids) &&
>- cpu_online(reboot_cpu))
>- reboot_cpu_id = reboot_cpu;
>-
>- /* Make certain the cpu I'm about to reboot on is online */
>- if (!cpu_online(reboot_cpu_id))
>- reboot_cpu_id = smp_processor_id();
>-
>- /* Make certain I only run on the appropriate processor */
>- set_cpus_allowed_ptr(current, cpumask_of(reboot_cpu_id));
>-
> /*
>- * O.K Now that I'm on the appropriate processor, stop all of the
>- * others. Also disable the local irq to not receive the per-cpu
>- * timer interrupt which may trigger scheduler's load balance.
>+ * Stop all of the others. Also disable the local irq to
>+ * not receive the per-cpu timer interrupt which may trigger
>+ * scheduler's load balance.
> */
> local_irq_disable();
> stop_other_cpus();
>diff --git a/kernel/reboot.c b/kernel/reboot.c
>index 187a0d8..9fbab07 100644
>--- a/kernel/reboot.c
>+++ b/kernel/reboot.c
>@@ -8,6 +8,7 @@
> #include <linux/kexec.h>
> #include <linux/kmod.h>
> #include <linux/kmsg_dump.h>
>+#include <linux/moduleparam.h>
> #include <linux/reboot.h>
> #include <linux/syscalls.h>
> #include <linux/syscore_ops.h>
>@@ -66,13 +67,18 @@ int unregister_reboot_notifier(struct
>notifier_block *nb)
> }
> EXPORT_SYMBOL(unregister_reboot_notifier);
>
>+int reboot_cpuid;
>+core_param(reboot_cpuid, reboot_cpuid, int, 0644);
>+
> void migrate_to_reboot_cpu(void)
> {
> /* The boot cpu is always logical cpu 0 */
>- int reboot_cpu_id = 0;
>+ int reboot_cpu_id = reboot_cpuid;
>
> /* Make certain the cpu I'm about to reboot on is online */
> if (!cpu_online(reboot_cpu_id))
>+ reboot_cpu_id = 0;
>+ if (!cpu_online(reboot_cpu_id))
> reboot_cpu_id = smp_processor_id();
>
> /* Prevent races with other tasks migrating this task. */
--
Sent from my mobile phone. Please excuse brevity and lack of formatting.
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