Add multi-reader, single-writer locks to kernel.

Any number of readers may be in the critical section at a time and writers
are mutually exclusive to all other threads. They are a better choice when
data is rarely modified but often read and multiple threads can safely
access it for reading.

Priority inheritance is fully implemented along with other changes to the
kernel to fully support it on multiowner objects.

This also cleans up priority code in the kernel and updates some associated
structures in existing objects to the cleaner form.

Currently doesn't add the mrsw_lock.[ch] files since they're not yet
needed by anything but the supporting improvements are still useful.

This includes a typed bitarray API (bitarray.h) which is pretty basic
for now.

Change-Id: Idbe43dcd9170358e06d48d00f1c69728ff45b0e3
Reviewed-on: http://gerrit.rockbox.org/801
Reviewed-by: Michael Sevakis <jethead71@rockbox.org>
Tested: Michael Sevakis <jethead71@rockbox.org>

1 files changed, 231 insertions, 0 deletions

diff --git a/firmware/include/bitarray.h b/firmware/include/bitarray.h
new file mode 100644
index 0000000000..4777ccb6a4
--- /dev/null
+++ b/firmware/include/bitarray.h
@@ -0,0 +1,231 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2014 by Michael Sevakis
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#ifndef BITARRAY_H
+#define BITARRAY_H
+
+/* Type-checked bit array definitions */
+
+/* All this stuff gets optimized into very simple object code */
+
+#define BITARRAY_WORD_BITS  \
+     (sizeof (unsigned int) * 8)
+#define BITARRAY_NWORDS(bits) \
+    (((bits) + BITARRAY_WORD_BITS - 1) / BITARRAY_WORD_BITS)
+#define BITARRAY_BITWORD(bitnum) \
+    ((bitnum) / BITARRAY_WORD_BITS)
+#define BITARRAY_WORDBIT(bitnum) \
+    ((bitnum) % BITARRAY_WORD_BITS)
+#define BITARRAY_NBIT(word, bit) \
+    ((word)*BITARRAY_WORD_BITS + (bit))
+#define BITARRAY_BITS(bits) \
+    (BITARRAY_NWORDS(bits)*BITARRAY_WORD_BITS)
+#define BITARRAY_BITN(bitnum) \
+    (1u << BITARRAY_WORDBIT(bitnum))
+
+
+/** Iterators **/
+#include "config.h"
+#include <stdint.h>
+
+#if (defined(CPU_ARM) && ARM_ARCH >= 5) || UINT32_MAX < UINT_MAX
+#define __BITARRAY_CTZ(wval)    __builtin_ctz(wval)
+#else
+#include "system.h"
+#define __BITARRAY_CTZ(wval)    find_first_set_bit(wval)
+#endif
+#define __BITARRAY_POPCNT(wval) __builtin_popcount(wval)
+
+#ifndef BIT_N
+#define BIT_N(n) (1u << (n))
+#endif
+
+/* Enumerate each word index */
+#define FOR_EACH_BITARRAY_WORD_INDEX(nwords, index) \
+    for (unsigned int index = 0, _nwords = (nwords); \
+         index < _nwords; index++)
+
+/* Enumerate each word value */
+#define FOR_EACH_BITARRAY_WORD(a, wval) \
+    FOR_EACH_BITARRAY_WORD_INDEX(ARRAYLEN((a)->words), _w) \
+        for (unsigned int wval = (a)->words[_w], _ = 1; _; _--)
+
+/* Enumerate the bit number of each set bit of a word in sequence */
+#define FOR_EACH_BITARRAY_SET_WORD_BIT(wval, bit) \
+    for (unsigned int _wval = (wval), bit;                 \
+         _wval ? (((bit) = __BITARRAY_CTZ(_wval)), 1) : 0; \
+         _wval &= ~BIT_N(bit))
+
+/* Enumerate the bit number of each set bit in the bit array in sequence */
+#define FOR_EACH_BITARRAY_SET_BIT_ARR(nwords, words, nbit) \
+    FOR_EACH_BITARRAY_WORD_INDEX(nwords, _w)               \
+        FOR_EACH_BITARRAY_SET_WORD_BIT(words[_w], _bit)    \
+            for (unsigned int nbit = BITARRAY_NBIT(_w, _bit), _ = 1; _; _--)
+
+/* As above but takes an array type for an argument */
+#define FOR_EACH_BITARRAY_SET_BIT(a, nbit) \
+    FOR_EACH_BITARRAY_SET_BIT_ARR(ARRAYLEN((a)->words), (a)->words, nbit)
+
+
+/** Base functions (called by typed functions) **/
+
+/* Return the word associated with the bit */
+static inline unsigned int
+__bitarray_get_word(unsigned int words[], unsigned int bitnum)
+{
+    return words[BITARRAY_BITWORD(bitnum)];
+}
+
+/* Set the word associated with the bit */
+static inline void
+__bitarray_set_word(unsigned int words[], unsigned int bitnum,
+                    unsigned int wordval)
+{
+    words[BITARRAY_BITWORD(bitnum)] = wordval;
+}
+
+/* Set the bit at index 'bitnum' to '1' */
+static inline void
+__bitarray_set_bit(unsigned int words[], unsigned int bitnum)
+{
+    unsigned int word = BITARRAY_BITWORD(bitnum);
+    unsigned int bit  = BITARRAY_BITN(bitnum);
+    words[word] |= bit;
+}
+
+/* Set the bit at index 'bitnum' to '0' */
+static inline void
+__bitarray_clear_bit(unsigned int words[], unsigned int bitnum)
+{
+    unsigned int word = BITARRAY_BITWORD(bitnum);
+    unsigned int bit  = BITARRAY_BITN(bitnum);
+    words[word] &= ~bit;
+}
+
+/* Return the value of the specified bit ('0' or '1') */
+static inline unsigned int
+__bitarray_test_bit(const unsigned int words[], unsigned int bitnum)
+{
+    unsigned int word = BITARRAY_BITWORD(bitnum);
+    unsigned int nbit = BITARRAY_WORDBIT(bitnum);
+    return (words[word] >> nbit) & 1u;
+}
+
+/* Check if all bits in the bit array are '0' */
+static inline bool
+__bitarray_is_clear(const unsigned int words[], unsigned int nbits)
+{
+    FOR_EACH_BITARRAY_WORD_INDEX(BITARRAY_NWORDS(nbits), word)
+    {
+        if (words[word] != 0)
+            return false;
+    }
+
+    return true;
+}
+
+/* Set every bit in the array to '0' */
+static inline void
+__bitarray_clear(unsigned int words[], unsigned int nbits)
+{
+    FOR_EACH_BITARRAY_WORD_INDEX(BITARRAY_NWORDS(nbits), word)
+        words[word] = 0;
+}
+
+/* Set every bit in the array to '1' */
+static inline void
+__bitarray_set(unsigned int words[], unsigned int nbits)
+{
+    FOR_EACH_BITARRAY_WORD_INDEX(BITARRAY_NWORDS(nbits), word)
+        words[word] = ~0u;
+}
+
+/* Find the lowest-indexed '1' bit in the bit array, returning the size of
+   the array if none are set */
+static inline unsigned int
+__bitarray_ffs(const unsigned int words[], unsigned int nbits)
+{
+    FOR_EACH_BITARRAY_SET_BIT_ARR(BITARRAY_NWORDS(nbits), words, nbit)
+        return nbit;
+
+    return BITARRAY_BITS(nbits);
+}
+
+/* Return the number of bits currently set to '1' in the bit array */
+static inline unsigned int
+__bitarray_popcount(const unsigned int words[], unsigned int nbits)
+{
+    unsigned int count = 0;
+
+    FOR_EACH_BITARRAY_WORD_INDEX(BITARRAY_NWORDS(nbits), word)
+        count += __BITARRAY_POPCNT(words[word]);
+
+    return count;
+}
+
+/**
+ * Giant macro to define all the typed functions
+ *   typename: The name of the type (e.g. myarr_t myarr;)
+ *   fnprefix: The prefix all functions get (e.g. myarr_set_bit)
+ *   nbits   : The minimum number of bits the array is meant to hold
+ *             (the implementation rounds this up to the word size
+ *              and all words may be fully utilized)
+ *
+ * uses 'typedef' to freely change from, e.g., struct to union without
+ * changing source code
+ */
+#define BITARRAY_TYPE_DECLARE(typename, fnprefix, nbits) \
+typedef struct                                                  \
+{                                                               \
+    unsigned int words[BITARRAY_NWORDS(nbits)];                 \
+} typename;                                                     \
+static inline unsigned int                                      \
+fnprefix##_get_word(typename *array, unsigned int bitnum)       \
+    { return __bitarray_get_word(array->words, bitnum); }       \
+static inline void                                              \
+fnprefix##_set_word(typename *array, unsigned int bitnum,       \
+                    unsigned int wordval)                       \
+    { __bitarray_set_word(array->words, bitnum, wordval); }     \
+static inline void                                              \
+fnprefix##_set_bit(typename *array, unsigned int bitnum)        \
+    { __bitarray_set_bit(array->words, bitnum); }               \
+static inline void                                              \
+fnprefix##_clear_bit(typename *array, unsigned int bitnum)      \
+    { __bitarray_clear_bit(array->words, bitnum); }             \
+static inline unsigned int                                      \
+fnprefix##_test_bit(const typename *array, unsigned int bitnum) \
+    { return __bitarray_test_bit(array->words, bitnum); }       \
+static inline bool                                              \
+fnprefix##_is_clear(const typename *array)                      \
+    { return __bitarray_is_clear(array->words, nbits); }        \
+static inline void                                              \
+fnprefix##_clear(typename *array)                               \
+    { __bitarray_clear(array->words, nbits); }                  \
+static inline void                                              \
+fnprefix##_set(typename *array)                                 \
+    { __bitarray_set(array->words, nbits); }                    \
+static inline unsigned int                                      \
+fnprefix##_ffs(const typename *array)                           \
+    { return __bitarray_ffs(array->words, nbits); }             \
+static inline unsigned int                                      \
+fnprefix##_popcount(const typename *array)                      \
+    { return __bitarray_popcount(array->words, nbits); }
+
+#endif /* BITARRAY_H */