| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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| 2 | #ifndef __LINUX_CPUMASK_TYPES_H |
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| 3 | #define __LINUX_CPUMASK_TYPES_H |
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| 4 | |
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| 5 | #include <linux/bitops.h> |
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| 6 | #include <linux/threads.h> |
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| 7 | |
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| 8 | /* Don't assign or return these: may not be this big! */ |
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| 9 | typedef struct cpumask { DECLARE_BITMAP(bits, NR_CPUS); } cpumask_t; |
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| 10 | |
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| 11 | /** |
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| 12 | * cpumask_bits - get the bits in a cpumask |
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| 13 | * @maskp: the struct cpumask * |
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| 14 | * |
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| 15 | * You should only assume nr_cpu_ids bits of this mask are valid. This is |
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| 16 | * a macro so it's const-correct. |
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| 17 | */ |
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| 18 | #define cpumask_bits(maskp) ((maskp)->bits) |
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| 19 | |
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| 20 | /* |
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| 21 | * cpumask_var_t: struct cpumask for stack usage. |
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| 22 | * |
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| 23 | * Oh, the wicked games we play! In order to make kernel coding a |
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| 24 | * little more difficult, we typedef cpumask_var_t to an array or a |
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| 25 | * pointer: doing &mask on an array is a noop, so it still works. |
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| 26 | * |
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| 27 | * i.e. |
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| 28 | * cpumask_var_t tmpmask; |
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| 29 | * if (!alloc_cpumask_var(&tmpmask, GFP_KERNEL)) |
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| 30 | * return -ENOMEM; |
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| 31 | * |
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| 32 | * ... use 'tmpmask' like a normal struct cpumask * ... |
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| 33 | * |
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| 34 | * free_cpumask_var(tmpmask); |
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| 35 | * |
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| 36 | * |
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| 37 | * However, one notable exception is there. alloc_cpumask_var() allocates |
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| 38 | * only nr_cpumask_bits bits (in the other hand, real cpumask_t always has |
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| 39 | * NR_CPUS bits). Therefore you don't have to dereference cpumask_var_t. |
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| 40 | * |
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| 41 | * cpumask_var_t tmpmask; |
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| 42 | * if (!alloc_cpumask_var(&tmpmask, GFP_KERNEL)) |
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| 43 | * return -ENOMEM; |
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| 44 | * |
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| 45 | * var = *tmpmask; |
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| 46 | * |
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| 47 | * This code makes NR_CPUS length memcopy and brings to a memory corruption. |
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| 48 | * cpumask_copy() provide safe copy functionality. |
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| 49 | * |
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| 50 | * Note that there is another evil here: If you define a cpumask_var_t |
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| 51 | * as a percpu variable then the way to obtain the address of the cpumask |
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| 52 | * structure differently influences what this_cpu_* operation needs to be |
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| 53 | * used. Please use this_cpu_cpumask_var_t in those cases. The direct use |
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| 54 | * of this_cpu_ptr() or this_cpu_read() will lead to failures when the |
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| 55 | * other type of cpumask_var_t implementation is configured. |
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| 56 | * |
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| 57 | * Please also note that __cpumask_var_read_mostly can be used to declare |
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| 58 | * a cpumask_var_t variable itself (not its content) as read mostly. |
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| 59 | */ |
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| 60 | #ifdef CONFIG_CPUMASK_OFFSTACK |
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| 61 | typedef struct cpumask *cpumask_var_t; |
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| 62 | #else |
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| 63 | typedef struct cpumask cpumask_var_t[1]; |
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| 64 | #endif /* CONFIG_CPUMASK_OFFSTACK */ |
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| 65 | |
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| 66 | #endif /* __LINUX_CPUMASK_TYPES_H */ |
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| 67 | |
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