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Message-ID: <20130415182258.GE3658@sgi.com>
Date: Mon, 15 Apr 2013 13:22:59 -0500
From: Robin Holt <holt@....com>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Robin Holt <holt@....com>, 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.
On Mon, Apr 15, 2013 at 10:47:49AM -0700, H. Peter Anvin wrote:
> 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?
How about:
Author: Robin Holt <holt@....com>
Date: Mon Apr 15 11:39:33 2013 -0500
Make reboot_cpuid a kernel parameter.
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.
I left a compatibility mode in there. The new parameter always
takes precedence. I also fixed up the current code to support
up to cpuid's up to the current max of 4096.
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>
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..cdcf28f 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
@@ -63,6 +59,8 @@ static int reboot_emergency;
/* This is set by the PCI code if either type 1 or type 2 PCI is detected */
bool port_cf9_safe = false;
+extern int reboot_cpuid;
+
/*
* reboot=b[ios] | s[mp] | t[riple] | k[bd] | e[fi] [, [w]arm | [c]old] | p[ci]
* warm Don't set the cold reboot flag
@@ -97,10 +95,14 @@ static int __init reboot_setup(char *str)
#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');
+ if (reboot_cpuid < 0) {
+ int coffset;
+
+ reboot_cpuid = 0;
+ for (coffset = 1; isdigit(*(str + coffset)); coffset++) {
+ reboot_cpuid *= 10;
+ reboot_cpuid += (int)(*(str+2) - '0');
+ }
}
/*
* We will leave sorting out the final value
@@ -615,25 +617,10 @@ 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..8d7b7d4 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 = -1;
+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. */
--
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