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Date: Mon, 15 Apr 2013 10:47:49 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Robin Holt <holt@....com>
CC: Ingo Molnar <mingo@...hat.com>, Russ Anderson <rja@....com>,
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.
We usually don't break working user setups as a matter if policy. Only if it can't be avoided.
Robin Holt <holt@....com> wrote:
>On Mon, Apr 15, 2013 at 10:18:31AM -0700, H. Peter Anvin wrote:
>> Um... doesn't this break anyone who currently depends on this?
>
>Yes. That is also why I kept this separate and not tagged for
>stable. They would need to start using the more general kernel
>parameter
>to get the same functionality. Should I have done it differently?
>
>Robin
>
>>
>> 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.
--
Sent from my mobile phone. Please excuse brevity and lack of formatting.
--
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