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Message-Id: <200902040115.09755.rusty@rustcorp.com.au>
Date: Wed, 4 Feb 2009 01:15:09 +1030
From: Rusty Russell <rusty@...tcorp.com.au>
To: James Bottomley <James.Bottomley@...senpartnership.com>
Cc: "linux-kernel" <linux-kernel@...r.kernel.org>,
Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] voyager: fix cpu bootmaps
On Sunday 01 February 2009 01:34:53 James Bottomley wrote:
> On Sat, 2009-01-31 at 23:27 +1030, Rusty Russell wrote:
> > On Saturday 31 January 2009 05:01:57 James Bottomley wrote: 3) << 24;
> > > - cpu_possible_map = phys_cpu_present_map;
> > > + init_cpu_possible(&phys_cpu_present_map);
...
> > Strange, the assignment should still work, even though this new method is
> > preferred.
>
> I know, it's weird ... it's like the compiler is copying to the lvalue
> but then discarding the result somehow
This makes me nervous. I may have broken other archs.
I'm testing the following patch now.
Thanks,
Rusty.
cpumask: avoid cast-away-const for deprecated cpu_*_map.
James Bottomley encountered a Voyager bug where gcc was discarding
changes to cpu_possible_map, which is now #defined to
cpu_possible_mask with the const cast away.
The modern way is to use init_cpu_possible or set_cpu_possible, but
not everyone is converted yet. I'm concerned that other archs might
have similar problems, so let's expose the underlying bits for the
moment (and prepend those names with __).
(This also makes accessing cpu_*_mask slightly more efficient, rather
than going via a pointer).
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
---
include/linux/cpumask.h | 28 +++++++++++++++++++---------
kernel/cpu.c | 44 ++++++++++++++++++++------------------------
2 files changed, 39 insertions(+), 33 deletions(-)
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -482,16 +482,26 @@ int __next_cpu_nr(int n, const cpumask_t
* only one CPU.
*/
-extern const struct cpumask *const cpu_possible_mask;
-extern const struct cpumask *const cpu_online_mask;
-extern const struct cpumask *const cpu_present_mask;
-extern const struct cpumask *const cpu_active_mask;
+#define cpu_possible_mask \
+ ((const struct cpumask *)to_cpumask(__cpu_possible_bits))
+#define cpu_online_mask \
+ ((const struct cpumask *)to_cpumask(__cpu_online_bits))
+#define cpu_present_mask \
+ ((const struct cpumask *)to_cpumask(__cpu_present_bits))
+#define cpu_active_mask \
+ ((const struct cpumask *)to_cpumask(__cpu_active_bits))
-/* These strip const, as traditionally they weren't const. */
-#define cpu_possible_map (*(cpumask_t *)cpu_possible_mask)
-#define cpu_online_map (*(cpumask_t *)cpu_online_mask)
-#define cpu_present_map (*(cpumask_t *)cpu_present_mask)
-#define cpu_active_map (*(cpumask_t *)cpu_active_mask)
+/* Deprecated non-const versions. */
+#define cpu_possible_map (*to_cpumask(__cpu_possible_bits))
+#define cpu_online_map (*to_cpumask(__cpu_online_bits))
+#define cpu_present_map (*to_cpumask(__cpu_present_bits))
+#define cpu_active_map (*to_cpumask(__cpu_active_bits))
+
+/* Don't use these directly: use cpu_*_mask, set_cpu_* or init_cpu_*. */
+extern unsigned long __cpu_possible_bits[];
+extern unsigned long __cpu_online_bits[];
+extern unsigned long __cpu_present_bits[];
+extern unsigned long __cpu_active_bits[];
#if NR_CPUS > 1
#define num_online_cpus() cpumask_weight(cpu_online_mask)
diff --git a/kernel/cpu.c b/kernel/cpu.c
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -499,69 +499,65 @@ EXPORT_SYMBOL(cpu_all_bits);
EXPORT_SYMBOL(cpu_all_bits);
#ifdef CONFIG_INIT_ALL_POSSIBLE
-static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
+DECLARE_BITMAP(__cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
= CPU_BITS_ALL;
#else
-static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
+DECLARE_BITMAP(__cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
#endif
-const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
-EXPORT_SYMBOL(cpu_possible_mask);
+EXPORT_SYMBOL(__cpu_possible_bits);
-static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
-const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
-EXPORT_SYMBOL(cpu_online_mask);
+DECLARE_BITMAP(__cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
+EXPORT_SYMBOL(__cpu_online_bits);
-static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
-const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
-EXPORT_SYMBOL(cpu_present_mask);
+DECLARE_BITMAP(__cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
+EXPORT_SYMBOL(__cpu_present_bits);
-static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
-const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
-EXPORT_SYMBOL(cpu_active_mask);
+DECLARE_BITMAP(__cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
+EXPORT_SYMBOL(__cpu_active_bits);
void set_cpu_possible(unsigned int cpu, bool possible)
{
if (possible)
- cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
+ cpumask_set_cpu(cpu, to_cpumask(__cpu_possible_bits));
else
- cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
+ cpumask_clear_cpu(cpu, to_cpumask(__cpu_possible_bits));
}
void set_cpu_present(unsigned int cpu, bool present)
{
if (present)
- cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
+ cpumask_set_cpu(cpu, to_cpumask(__cpu_present_bits));
else
- cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
+ cpumask_clear_cpu(cpu, to_cpumask(__cpu_present_bits));
}
void set_cpu_online(unsigned int cpu, bool online)
{
if (online)
- cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
+ cpumask_set_cpu(cpu, to_cpumask(__cpu_online_bits));
else
- cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
+ cpumask_clear_cpu(cpu, to_cpumask(__cpu_online_bits));
}
void set_cpu_active(unsigned int cpu, bool active)
{
if (active)
- cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
+ cpumask_set_cpu(cpu, to_cpumask(__cpu_active_bits));
else
- cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
+ cpumask_clear_cpu(cpu, to_cpumask(__cpu_active_bits));
}
void init_cpu_present(const struct cpumask *src)
{
- cpumask_copy(to_cpumask(cpu_present_bits), src);
+ cpumask_copy(to_cpumask(__cpu_present_bits), src);
}
void init_cpu_possible(const struct cpumask *src)
{
- cpumask_copy(to_cpumask(cpu_possible_bits), src);
+ cpumask_copy(to_cpumask(__cpu_possible_bits), src);
}
void init_cpu_online(const struct cpumask *src)
{
- cpumask_copy(to_cpumask(cpu_online_bits), src);
+ cpumask_copy(to_cpumask(__cpu_online_bits), src);
}
--
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