Re: [PATCH -v5 5/5] Make reboot_cpuid a kernel parameter.
From: Robin Holt
Date: Wed Apr 17 2013 - 22:05:24 EST
On Wed, Apr 17, 2013 at 08:25:39PM -0500, Robin Holt wrote:
> On Wed, Apr 17, 2013 at 05:39:33PM -0700, H. Peter Anvin wrote:
> > On 04/17/2013 05:17 PM, Robin Holt wrote:
> > >
> > > There are 4 items being parsed out of reboot= for x86:
> > > - reboot_mode w[arm] | c[old]
> > > - reboot_cpu s[mp]####
> > > - reboot_type b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]
> > > - reboot_force f[orce]
> > >
> > > This seems like a lot to push into the generic kernel just to make it
> > > appear consistent when there will be no real cross arch consistency.
> > >
> > > Contrast that with:
> > > 1) New kernel parameter (reboot_cpu) which is clear and concise, uses standard
> > > parsing methods.
> > > 2) Backwards compatibility in that a user with an existing (broken) reboot=s32
> > > on the command line will set reboot_cpu unless both were specified, in which
> > > case reboot_cpu takes precedence.
> > >
> > > What is so fundamentally wrong with that? It accomplishes exactly what
> > > you had asked for in that existing users are not broken. We are introducing
> > > a new functionality in the general kernel. Why not introduce a new parameter
> > > associated with that functionality.
> > >
> >
> > You are confusing implementation with interface. That is what is so
> > fundamentally wrong with that. You really, really don't want to change
> > interface unless the world will end if you don't.
> >
> > As far as why centralize -- the main concern I have is that someone
> > might try to introduce an arch-specific reboot= which is *syntactically*
> > different, which is yet again really awful from a user perspective.
>
> Yes and no. I am saying that the interface is garbage and already
> specified as arch specific. You are asking me to take that garbage
> interface and promote it to a general interface which will force us to
> implement it in a completely crappy way.
>
> Compare that with introducing a new interface which is concise and then
> providing backwards compatibility. Add to that the fact, I don't need
> to pollute the kernel with some poorly done x86 interface and leave that
> cruft for others to clean up.
OK. Here goes:
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4609e81..35af99e 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2593,9 +2593,17 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
Run specified binary instead of /init from the ramdisk,
used for early userspace startup. See initrd.
- reboot= [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
- Format: <reboot_mode>[,<reboot_mode2>[,...]]
- See arch/*/kernel/reboot.c or arch/*/kernel/process.c
+ reboot= [KNL]
+ Format:
+ [w[arm] | c[old]] \
+ [,b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
+ [,f[orce] \
+ [,] s[mp]####
+ Where reboot_mode is one of warm or cold,
+ reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
+ reboot_force is either force or not specified,
+ and reboot_cpu is s[mp]#### with #### being the
+ processor to be used for rebooting.
relax_domain_level=
[KNL, SMP] Set scheduler's default relax_domain_level.
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 76fa1e9..f9e8bf4 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -36,22 +36,11 @@ void (*pm_power_off)(void);
EXPORT_SYMBOL(pm_power_off);
static const struct desc_ptr no_idt = {};
-static int reboot_mode;
-enum reboot_type reboot_type = BOOT_ACPI;
-int reboot_force;
+extern int reboot_mode;
+extern enum reboot_type reboot_type;
+extern int reboot_force;
-/*
- * This variable is used privately to keep track of whether or not
- * reboot_type is still set to its default value (i.e., reboot= hasn't
- * been set on the command line). This is needed so that we can
- * suppress DMI scanning for reboot quirks. Without it, it's
- * impossible to override a faulty reboot quirk without recompiling.
- */
-static int reboot_default = 1;
-
-#ifdef CONFIG_SMP
-static int reboot_cpu = -1;
-#endif
+extern int reboot_default;
/*
* This is set if we need to go through the 'emergency' path.
@@ -63,78 +52,6 @@ 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;
-/*
- * 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
- * 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
- * efi Use efi reset_system runtime service
- * pci Use the so-called "PCI reset register", CF9
- * force Avoid anything that could hang.
- */
-static int __init reboot_setup(char *str)
-{
- for (;;) {
- /*
- * Having anything passed on the command line via
- * reboot= will cause us to disable DMI checking
- * below.
- */
- reboot_default = 0;
-
- switch (*str) {
- case 'w':
- reboot_mode = 0x1234;
- break;
-
- case 'c':
- 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':
- case 't':
- case 'e':
- case 'p':
- reboot_type = *str;
- break;
-
- case 'f':
- reboot_force = 1;
- break;
- }
-
- str = strchr(str, ',');
- if (str)
- str++;
- else
- break;
- }
- return 1;
-}
-
-__setup("reboot=", reboot_setup);
-
/*
* Reboot options and system auto-detection code provided by
@@ -614,26 +531,10 @@ 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 7f4658f..3448a1d 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -6,6 +6,7 @@
#define pr_fmt(fmt) "reboot: " fmt
+#include <linux/ctype.h>
#include <linux/export.h>
#include <linux/kexec.h>
#include <linux/kmod.h>
@@ -69,22 +70,107 @@ int unregister_reboot_notifier(struct notifier_block *nb)
}
EXPORT_SYMBOL(unregister_reboot_notifier);
+/*
+ * This variable is used privately to keep track of whether or not
+ * reboot_type is still set to its default value (i.e., reboot= hasn't
+ * been set on the command line). This is needed so that we can
+ * suppress DMI scanning for reboot quirks. Without it, it's
+ * impossible to override a faulty reboot quirk without recompiling.
+ */
+int reboot_default = 1;
+int reboot_mode;
+enum reboot_type reboot_type = BOOT_ACPI;
+int reboot_force;
+static int reboot_cpu;
+
+/*
+ * 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
+ * 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
+ * efi Use efi reset_system runtime service
+ * pci Use the so-called "PCI reset register", CF9
+ * force Avoid anything that could hang.
+ */
+static int __init reboot_setup(char *str)
+{
+ int i;
+
+ for (;;) {
+ /*
+ * Having anything passed on the command line via
+ * reboot= will cause us to disable DMI checking
+ * below.
+ */
+ reboot_default = 0;
+
+ switch (*str) {
+ case 'w':
+ reboot_mode = 0x1234;
+ break;
+
+ case 'c':
+ reboot_mode = 0;
+ break;
+
+#ifdef CONFIG_SMP
+ case 's':
+ if (*(str + 1) == 'm' && *(str + 2) == 'p')
+ str += 2;
+
+ reboot_cpu = 0;
+ for (i = 1; isdigit(*(str + i)); i++) {
+ reboot_cpu *= 10;
+ reboot_cpu += (int)(*(str + i) - '0');
+ }
+
+ break;
+#endif /* CONFIG_SMP */
+
+ case 'b':
+ case 'a':
+ case 'k':
+ case 't':
+ case 'e':
+ case 'p':
+ reboot_type = *str;
+ break;
+
+ case 'f':
+ reboot_force = 1;
+ break;
+ }
+
+ str = strchr(str, ',');
+ if (str)
+ str++;
+ else
+ break;
+ }
+ return 1;
+}
+__setup("reboot=", reboot_setup);
+
+
static void migrate_to_reboot_cpu(void)
{
- /* The boot cpu is always logical cpu 0 */
- int reboot_cpu_id = 0;
+ int cpu = reboot_cpu;
cpu_hotplug_disable();
/* Make certain the cpu I'm about to reboot on is online */
- if (!cpu_online(reboot_cpu_id))
- reboot_cpu_id = cpumask_first(cpu_online_mask);
+ if (!cpu_online(cpu))
+ cpu = cpumask_first(cpu_online_mask);
/* Prevent races with other tasks migrating this task */
current->flags |= PF_THREAD_BOUND;
/* Make certain I only run on the appropriate processor */
- set_cpus_allowed_ptr(current, cpumask_of(reboot_cpu_id));
+ set_cpus_allowed_ptr(current, cpumask_of(cpu));
}
/**
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