+++ /dev/null
-#ifndef _LINUX_RING_BUFFER_BACKEND_INTERNAL_H
-#define _LINUX_RING_BUFFER_BACKEND_INTERNAL_H
-
-/*
- * linux/ringbuffer/backend_internal.h
- *
- * Copyright (C) 2008-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *
- * Ring buffer backend (internal helpers).
- *
- * Dual LGPL v2.1/GPL v2 license.
- */
-
-#include <unistd.h>
-#include <urcu/compiler.h>
-
-#include <ust/ringbuffer-config.h>
-#include "backend_types.h"
-#include "frontend_types.h"
-#include "shm.h"
-
-/* Ring buffer backend API presented to the frontend */
-
-/* Ring buffer and channel backend create/free */
-
-int lib_ring_buffer_backend_create(struct lib_ring_buffer_backend *bufb,
- struct channel_backend *chan, int cpu,
- struct shm_handle *handle,
- struct shm_object *shmobj);
-void channel_backend_unregister_notifiers(struct channel_backend *chanb);
-void lib_ring_buffer_backend_free(struct lib_ring_buffer_backend *bufb);
-int channel_backend_init(struct channel_backend *chanb,
- const char *name,
- const struct lib_ring_buffer_config *config,
- void *priv, size_t subbuf_size,
- size_t num_subbuf, struct shm_handle *handle);
-void channel_backend_free(struct channel_backend *chanb,
- struct shm_handle *handle);
-
-void lib_ring_buffer_backend_reset(struct lib_ring_buffer_backend *bufb,
- struct shm_handle *handle);
-void channel_backend_reset(struct channel_backend *chanb);
-
-int lib_ring_buffer_backend_init(void);
-void lib_ring_buffer_backend_exit(void);
-
-extern void _lib_ring_buffer_write(struct lib_ring_buffer_backend *bufb,
- size_t offset, const void *src, size_t len,
- ssize_t pagecpy);
-
-/*
- * Subbuffer ID bits for overwrite mode. Need to fit within a single word to be
- * exchanged atomically.
- *
- * Top half word, except lowest bit, belongs to "offset", which is used to keep
- * to count the produced buffers. For overwrite mode, this provides the
- * consumer with the capacity to read subbuffers in order, handling the
- * situation where producers would write up to 2^15 buffers (or 2^31 for 64-bit
- * systems) concurrently with a single execution of get_subbuf (between offset
- * sampling and subbuffer ID exchange).
- */
-
-#define HALF_ULONG_BITS (CAA_BITS_PER_LONG >> 1)
-
-#define SB_ID_OFFSET_SHIFT (HALF_ULONG_BITS + 1)
-#define SB_ID_OFFSET_COUNT (1UL << SB_ID_OFFSET_SHIFT)
-#define SB_ID_OFFSET_MASK (~(SB_ID_OFFSET_COUNT - 1))
-/*
- * Lowest bit of top word half belongs to noref. Used only for overwrite mode.
- */
-#define SB_ID_NOREF_SHIFT (SB_ID_OFFSET_SHIFT - 1)
-#define SB_ID_NOREF_COUNT (1UL << SB_ID_NOREF_SHIFT)
-#define SB_ID_NOREF_MASK SB_ID_NOREF_COUNT
-/*
- * In overwrite mode: lowest half of word is used for index.
- * Limit of 2^16 subbuffers per buffer on 32-bit, 2^32 on 64-bit.
- * In producer-consumer mode: whole word used for index.
- */
-#define SB_ID_INDEX_SHIFT 0
-#define SB_ID_INDEX_COUNT (1UL << SB_ID_INDEX_SHIFT)
-#define SB_ID_INDEX_MASK (SB_ID_NOREF_COUNT - 1)
-
-/*
- * Construct the subbuffer id from offset, index and noref. Use only the index
- * for producer-consumer mode (offset and noref are only used in overwrite
- * mode).
- */
-static inline
-unsigned long subbuffer_id(const struct lib_ring_buffer_config *config,
- unsigned long offset, unsigned long noref,
- unsigned long index)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- return (offset << SB_ID_OFFSET_SHIFT)
- | (noref << SB_ID_NOREF_SHIFT)
- | index;
- else
- return index;
-}
-
-/*
- * Compare offset with the offset contained within id. Return 1 if the offset
- * bits are identical, else 0.
- */
-static inline
-int subbuffer_id_compare_offset(const struct lib_ring_buffer_config *config,
- unsigned long id, unsigned long offset)
-{
- return (id & SB_ID_OFFSET_MASK) == (offset << SB_ID_OFFSET_SHIFT);
-}
-
-static inline
-unsigned long subbuffer_id_get_index(const struct lib_ring_buffer_config *config,
- unsigned long id)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- return id & SB_ID_INDEX_MASK;
- else
- return id;
-}
-
-static inline
-unsigned long subbuffer_id_is_noref(const struct lib_ring_buffer_config *config,
- unsigned long id)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- return !!(id & SB_ID_NOREF_MASK);
- else
- return 1;
-}
-
-/*
- * Only used by reader on subbuffer ID it has exclusive access to. No volatile
- * needed.
- */
-static inline
-void subbuffer_id_set_noref(const struct lib_ring_buffer_config *config,
- unsigned long *id)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- *id |= SB_ID_NOREF_MASK;
-}
-
-static inline
-void subbuffer_id_set_noref_offset(const struct lib_ring_buffer_config *config,
- unsigned long *id, unsigned long offset)
-{
- unsigned long tmp;
-
- if (config->mode == RING_BUFFER_OVERWRITE) {
- tmp = *id;
- tmp &= ~SB_ID_OFFSET_MASK;
- tmp |= offset << SB_ID_OFFSET_SHIFT;
- tmp |= SB_ID_NOREF_MASK;
- /* Volatile store, read concurrently by readers. */
- CMM_ACCESS_ONCE(*id) = tmp;
- }
-}
-
-/* No volatile access, since already used locally */
-static inline
-void subbuffer_id_clear_noref(const struct lib_ring_buffer_config *config,
- unsigned long *id)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- *id &= ~SB_ID_NOREF_MASK;
-}
-
-/*
- * For overwrite mode, cap the number of subbuffers per buffer to:
- * 2^16 on 32-bit architectures
- * 2^32 on 64-bit architectures
- * This is required to fit in the index part of the ID. Return 0 on success,
- * -EPERM on failure.
- */
-static inline
-int subbuffer_id_check_index(const struct lib_ring_buffer_config *config,
- unsigned long num_subbuf)
-{
- if (config->mode == RING_BUFFER_OVERWRITE)
- return (num_subbuf > (1UL << HALF_ULONG_BITS)) ? -EPERM : 0;
- else
- return 0;
-}
-
-static inline
-void subbuffer_count_record(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx, struct shm_handle *handle)
-{
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, shmp(handle, bufb->buf_wsb)[idx].id);
- v_inc(config, &shmp(handle, (shmp(handle, bufb->array)[sb_bindex]).shmp)->records_commit);
-}
-
-/*
- * Reader has exclusive subbuffer access for record consumption. No need to
- * perform the decrement atomically.
- */
-static inline
-void subbuffer_consume_record(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- struct shm_handle *handle)
-{
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
- CHAN_WARN_ON(shmp(handle, bufb->chan),
- !v_read(config, &shmp(handle, (shmp(handle, bufb->array)[sb_bindex]).shmp)->records_unread));
- /* Non-atomic decrement protected by exclusive subbuffer access */
- _v_dec(config, &shmp(handle, (shmp(handle, bufb->array)[sb_bindex]).shmp)->records_unread);
- v_inc(config, &bufb->records_read);
-}
-
-static inline
-unsigned long subbuffer_get_records_count(
- const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx,
- struct shm_handle *handle)
-{
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, shmp(handle, bufb->buf_wsb)[idx].id);
- return v_read(config, &shmp(handle, (shmp(handle, bufb->array)[sb_bindex]).shmp)->records_commit);
-}
-
-/*
- * Must be executed at subbuffer delivery when the writer has _exclusive_
- * subbuffer access. See ring_buffer_check_deliver() for details.
- * ring_buffer_get_records_count() must be called to get the records count
- * before this function, because it resets the records_commit count.
- */
-static inline
-unsigned long subbuffer_count_records_overrun(
- const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx,
- struct shm_handle *handle)
-{
- struct lib_ring_buffer_backend_pages_shmp *pages;
- unsigned long overruns, sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, shmp(handle, bufb->buf_wsb)[idx].id);
- pages = &shmp(handle, bufb->array)[sb_bindex];
- overruns = v_read(config, &shmp(handle, pages->shmp)->records_unread);
- v_set(config, &shmp(handle, pages->shmp)->records_unread,
- v_read(config, &shmp(handle, pages->shmp)->records_commit));
- v_set(config, &shmp(handle, pages->shmp)->records_commit, 0);
-
- return overruns;
-}
-
-static inline
-void subbuffer_set_data_size(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx,
- unsigned long data_size,
- struct shm_handle *handle)
-{
- struct lib_ring_buffer_backend_pages_shmp *pages;
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, shmp(handle, bufb->buf_wsb)[idx].id);
- pages = &shmp(handle, bufb->array)[sb_bindex];
- shmp(handle, pages->shmp)->data_size = data_size;
-}
-
-static inline
-unsigned long subbuffer_get_read_data_size(
- const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- struct shm_handle *handle)
-{
- struct lib_ring_buffer_backend_pages_shmp *pages;
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, bufb->buf_rsb.id);
- pages = &shmp(handle, bufb->array)[sb_bindex];
- return shmp(handle, pages->shmp)->data_size;
-}
-
-static inline
-unsigned long subbuffer_get_data_size(
- const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx,
- struct shm_handle *handle)
-{
- struct lib_ring_buffer_backend_pages_shmp *pages;
- unsigned long sb_bindex;
-
- sb_bindex = subbuffer_id_get_index(config, shmp(handle, bufb->buf_wsb)[idx].id);
- pages = &shmp(handle, bufb->array)[sb_bindex];
- return shmp(handle, pages->shmp)->data_size;
-}
-
-/**
- * lib_ring_buffer_clear_noref - Clear the noref subbuffer flag, called by
- * writer.
- */
-static inline
-void lib_ring_buffer_clear_noref(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx,
- struct shm_handle *handle)
-{
- unsigned long id, new_id;
-
- if (config->mode != RING_BUFFER_OVERWRITE)
- return;
-
- /*
- * Performing a volatile access to read the sb_pages, because we want to
- * read a coherent version of the pointer and the associated noref flag.
- */
- id = CMM_ACCESS_ONCE(shmp(handle, bufb->buf_wsb)[idx].id);
- for (;;) {
- /* This check is called on the fast path for each record. */
- if (likely(!subbuffer_id_is_noref(config, id))) {
- /*
- * Store after load dependency ordering the writes to
- * the subbuffer after load and test of the noref flag
- * matches the memory barrier implied by the cmpxchg()
- * in update_read_sb_index().
- */
- return; /* Already writing to this buffer */
- }
- new_id = id;
- subbuffer_id_clear_noref(config, &new_id);
- new_id = uatomic_cmpxchg(&shmp(handle, bufb->buf_wsb)[idx].id, id, new_id);
- if (likely(new_id == id))
- break;
- id = new_id;
- }
-}
-
-/**
- * lib_ring_buffer_set_noref_offset - Set the noref subbuffer flag and offset,
- * called by writer.
- */
-static inline
-void lib_ring_buffer_set_noref_offset(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- unsigned long idx, unsigned long offset,
- struct shm_handle *handle)
-{
- if (config->mode != RING_BUFFER_OVERWRITE)
- return;
-
- /*
- * Because ring_buffer_set_noref() is only called by a single thread
- * (the one which updated the cc_sb value), there are no concurrent
- * updates to take care of: other writers have not updated cc_sb, so
- * they cannot set the noref flag, and concurrent readers cannot modify
- * the pointer because the noref flag is not set yet.
- * The smp_wmb() in ring_buffer_commit() takes care of ordering writes
- * to the subbuffer before this set noref operation.
- * subbuffer_set_noref() uses a volatile store to deal with concurrent
- * readers of the noref flag.
- */
- CHAN_WARN_ON(shmp(handle, bufb->chan),
- subbuffer_id_is_noref(config, shmp(handle, bufb->buf_wsb)[idx].id));
- /*
- * Memory barrier that ensures counter stores are ordered before set
- * noref and offset.
- */
- cmm_smp_mb();
- subbuffer_id_set_noref_offset(config, &shmp(handle, bufb->buf_wsb)[idx].id, offset);
-}
-
-/**
- * update_read_sb_index - Read-side subbuffer index update.
- */
-static inline
-int update_read_sb_index(const struct lib_ring_buffer_config *config,
- struct lib_ring_buffer_backend *bufb,
- struct channel_backend *chanb,
- unsigned long consumed_idx,
- unsigned long consumed_count,
- struct shm_handle *handle)
-{
- unsigned long old_id, new_id;
-
- if (config->mode == RING_BUFFER_OVERWRITE) {
- /*
- * Exchange the target writer subbuffer with our own unused
- * subbuffer. No need to use CMM_ACCESS_ONCE() here to read the
- * old_wpage, because the value read will be confirmed by the
- * following cmpxchg().
- */
- old_id = shmp(handle, bufb->buf_wsb)[consumed_idx].id;
- if (unlikely(!subbuffer_id_is_noref(config, old_id)))
- return -EAGAIN;
- /*
- * Make sure the offset count we are expecting matches the one
- * indicated by the writer.
- */
- if (unlikely(!subbuffer_id_compare_offset(config, old_id,
- consumed_count)))
- return -EAGAIN;
- CHAN_WARN_ON(shmp(handle, bufb->chan),
- !subbuffer_id_is_noref(config, bufb->buf_rsb.id));
- subbuffer_id_set_noref_offset(config, &bufb->buf_rsb.id,
- consumed_count);
- new_id = uatomic_cmpxchg(&shmp(handle, bufb->buf_wsb)[consumed_idx].id, old_id,
- bufb->buf_rsb.id);
- if (unlikely(old_id != new_id))
- return -EAGAIN;
- bufb->buf_rsb.id = new_id;
- } else {
- /* No page exchange, use the writer page directly */
- bufb->buf_rsb.id = shmp(handle, bufb->buf_wsb)[consumed_idx].id;
- }
- return 0;
-}
-
-/*
- * Use the architecture-specific memcpy implementation for constant-sized
- * inputs, but rely on an inline memcpy for length statically unknown.
- * The function call to memcpy is just way too expensive for a fast path.
- */
-#define lib_ring_buffer_do_copy(config, dest, src, len) \
-do { \
- size_t __len = (len); \
- if (__builtin_constant_p(len)) \
- memcpy(dest, src, __len); \
- else \
- inline_memcpy(dest, src, __len); \
-} while (0)
-
-#endif /* _LINUX_RING_BUFFER_BACKEND_INTERNAL_H */
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