We want to move cpumasks off the stack: no local decls, no passing by copy. Linus suggested we use the array-or-pointer trick for on-stack vars; we introduce a new cpumask_var_t for this. Rather than pick an arbitrary limit, I chose a new config option so arch maintainers can decide where their threshold is. From: Rusty Russell <rusty@xxxxxxxxxxxxxxx> Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx> Signed-off-by: Mike Travis <travis@xxxxxxx> --- include/linux/cpumask.h | 36 ++++++++++++++++++++++++++++++++++++ lib/cpumask.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 67 insertions(+) --- test-compile.orig/include/linux/cpumask.h +++ test-compile/include/linux/cpumask.h @@ -485,6 +485,42 @@ int __next_cpu_nr(int n, const cpumask_t #endif /* NR_CPUS > 64 */ /* + * cpumask_var_t: struct cpumask for stack usage. + * + * Oh, the wicked games we play! In order to make kernel coding a + * little more difficult, we typedef cpumask_var_t to an array or a + * pointer: doing &mask on an array is a noop, so it still works. + * + * ie. + * cpumask_var_t tmpmask; + * if (!alloc_cpumask_var(&tmpmask, GFP_KERNEL)) + * return -ENOMEM; + * + * ... use 'tmpmask' like a normal struct cpumask * ... + * + * free_cpumask_var(tmpmask); + */ +#ifdef CONFIG_CPUMASK_OFFSTACK +typedef struct cpumask *cpumask_var_t; + +bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags); +void free_cpumask_var(cpumask_var_t mask); + +#else +typedef struct cpumask cpumask_var_t[1]; + +static inline bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags) +{ + return true; +} + +static inline void free_cpumask_var(cpumask_var_t mask) +{ +} + +#endif /* CONFIG_CPUMASK_OFFSTACK */ + +/* * The following particular system cpumasks and operations manage * possible, present, active and online cpus. Each of them is a fixed size * bitmap of size NR_CPUS. --- test-compile.orig/lib/cpumask.c +++ test-compile/lib/cpumask.c @@ -43,3 +43,34 @@ int __any_online_cpu(const cpumask_t *ma return cpu; } EXPORT_SYMBOL(__any_online_cpu); + +/* These are not inline because of header tangles. */ +#ifdef CONFIG_CPUMASK_OFFSTACK +bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags) +{ + if (likely(slab_is_available())) + *mask = kmalloc(BITS_TO_LONGS(nr_cpu_ids)*sizeof(long), flags); + else { +#ifdef CONFIG_DEBUG_PER_CPU_MAPS + printk(KERN_ERR + "=> alloc_cpumask_var: kmalloc not available!\n"); + dump_stack(); +#endif + *mask = NULL; + } +#ifdef CONFIG_DEBUG_PER_CPU_MAPS + if (!*mask) { + printk(KERN_ERR "=> alloc_cpumask_var: failed!\n"); + dump_stack(); + } +#endif + return *mask != NULL; +} +EXPORT_SYMBOL(alloc_cpumask_var); + +void free_cpumask_var(cpumask_var_t mask) +{ + kfree(mask); +} +EXPORT_SYMBOL(free_cpumask_var); +#endif -- -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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