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| 5 | #ifndef _TRACE_INTERNAL_PID_LIST_H
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| 6 | #define _TRACE_INTERNAL_PID_LIST_H
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| 7 |
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| 8 | |
| 9 | * In order to keep track of what pids to trace, a tree is created much
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| 10 | * like page tables are used. This creates a sparse bit map, where
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| 11 | * the tree is filled in when needed. A PID is at most 30 bits (see
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| 12 | * linux/thread.h), and is broken up into 3 sections based on the bit map
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| 13 | * of the bits. The 8 MSB is the "upper1" section. The next 8 MSB is the
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| 14 | * "upper2" section and the 14 LSB is the "lower" section.
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| 15 | *
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| 16 | * A trace_pid_list structure holds the "upper1" section, in an
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| 17 | * array of 256 pointers (1 or 2K in size) to "upper_chunk" unions, where
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| 18 | * each has an array of 256 pointers (1 or 2K in size) to the "lower_chunk"
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| 19 | * structures, where each has an array of size 2K bytes representing a bitmask
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| 20 | * of the 14 LSB of the PID (256 * 8 = 2048)
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| 21 | *
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| 22 | * When a trace_pid_list is allocated, it includes the 256 pointer array
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| 23 | * of the upper1 unions. Then a "cache" of upper and lower is allocated
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| 24 | * where these will be assigned as needed.
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| 25 | *
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| 26 | * When a bit is set in the pid_list bitmask, the pid to use has
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| 27 | * the 8 MSB masked, and this is used to index the array in the
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| 28 | * pid_list to find the next upper union. If the element is NULL,
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| 29 | * then one is retrieved from the upper_list cache. If none is
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| 30 | * available, then -ENOMEM is returned.
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| 31 | *
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| 32 | * The next 8 MSB is used to index into the "upper2" section. If this
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| 33 | * element is NULL, then it is retrieved from the lower_list cache.
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| 34 | * Again, if one is not available -ENOMEM is returned.
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| 35 | *
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| 36 | * Finally the 14 LSB of the PID is used to set the bit in the 16384
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| 37 | * bitmask (made up of 2K bytes).
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| 38 | *
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| 39 | * When the second upper section or the lower section has their last
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| 40 | * bit cleared, they are added back to the free list to be reused
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| 41 | * when needed.
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| 42 |
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| 43 |
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| 44 | #define UPPER_BITS 8
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| 45 | #define UPPER_MAX (1 << UPPER_BITS)
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| 46 | #define UPPER1_SIZE (1 << UPPER_BITS)
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| 47 | #define UPPER2_SIZE (1 << UPPER_BITS)
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| 48 |
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| 49 | #define LOWER_BITS 14
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| 50 | #define LOWER_MAX (1 << LOWER_BITS)
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| 51 | #define LOWER_SIZE (LOWER_MAX / BITS_PER_LONG)
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| 52 |
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| 53 | #define UPPER1_SHIFT (LOWER_BITS + UPPER_BITS)
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| 54 | #define UPPER2_SHIFT LOWER_BITS
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| 55 | #define LOWER_MASK (LOWER_MAX - 1)
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| 56 |
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| 57 | #define UPPER_MASK (UPPER_MAX - 1)
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| 58 |
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| 59 |
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| 60 | #define MAX_PID (1 << 30)
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| 61 |
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| 62 |
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| 63 | #define CHUNK_ALLOC 6
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| 64 |
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| 65 |
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| 66 | #define CHUNK_REALLOC 2
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| 67 |
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| 68 | union lower_chunk {
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| 69 | union lower_chunk *next;
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| 70 | unsigned long data[LOWER_SIZE]; |
| 71 | };
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| 72 |
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| 73 | union upper_chunk {
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| 74 | union upper_chunk *next;
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| 75 | union lower_chunk *data[UPPER2_SIZE]; |
| 76 | };
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| 77 |
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| 78 | struct trace_pid_list {
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| 79 | seqcount_raw_spinlock_t seqcount;
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| 80 | raw_spinlock_t lock;
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| 81 | struct irq_work refill_irqwork;
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| 82 | union upper_chunk *upper[UPPER1_SIZE]; |
| 83 | union upper_chunk *upper_list;
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| 84 | union lower_chunk *lower_list;
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| 85 | int free_upper_chunks;
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| 86 | int free_lower_chunks;
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| 87 | };
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| 88 |
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| 89 | #endif
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