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Date: Tue, 16 Apr 2013 05:05:45 -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>,
Joe Perches <joe@...ches.com>,
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 -v4 4/4] Make reboot_cpuid a kernel parameter. other cpus.
Why not just support the existing syntax everywhere?
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.
>
>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>
>
>---
>
>Changes since -v3
>- Added a reboot=s#### compatibility mode for x86.
>
> Documentation/kernel-parameters.txt | 2 ++
>arch/x86/kernel/reboot.c | 39
>+++++++++++++------------------------
> kernel/reboot.c | 8 +++++++-
> 3 files changed, 22 insertions(+), 27 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..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 8cfef20..b2ef798 100644
>--- a/kernel/reboot.c
>+++ b/kernel/reboot.c
>@@ -10,6 +10,7 @@
> #include <linux/kexec.h>
> #include <linux/kmod.h>
> #include <linux/kmsg_dump.h>
>+#include <linux/moduleparam.h>
> #include <linux/reboot.h>
> #include <linux/suspend.h>
> #include <linux/syscalls.h>
>@@ -69,13 +70,18 @@ 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. */
--
Sent from my mobile phone. Please excuse brevity and lack of formatting.
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