301 lines
8.8 KiB
C
301 lines
8.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* linux/include/linux/relay.h
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*
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* Copyright (C) 2002, 2003 - Tom Zanussi (zanussi@us.ibm.com), IBM Corp
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* Copyright (C) 1999, 2000, 2001, 2002 - Karim Yaghmour (karim@opersys.com)
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*
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* CONFIG_RELAY definitions and declarations
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*/
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#ifndef _LINUX_RELAY_H
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#define _LINUX_RELAY_H
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#include <linux/types.h>
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#include <linux/sched.h>
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#include <linux/timer.h>
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#include <linux/wait.h>
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#include <linux/list.h>
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#include <linux/irq_work.h>
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#include <linux/bug.h>
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#include <linux/fs.h>
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#include <linux/poll.h>
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#include <linux/kref.h>
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#include <linux/percpu.h>
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/*
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* Tracks changes to rchan/rchan_buf structs
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*/
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#define RELAYFS_CHANNEL_VERSION 7
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/*
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* Per-cpu relay channel buffer
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*/
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struct rchan_buf
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{
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void *start; /* start of channel buffer */
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void *data; /* start of current sub-buffer */
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size_t offset; /* current offset into sub-buffer */
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size_t subbufs_produced; /* count of sub-buffers produced */
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size_t subbufs_consumed; /* count of sub-buffers consumed */
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struct rchan *chan; /* associated channel */
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wait_queue_head_t read_wait; /* reader wait queue */
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struct irq_work wakeup_work; /* reader wakeup */
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struct dentry *dentry; /* channel file dentry */
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struct kref kref; /* channel buffer refcount */
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struct page **page_array; /* array of current buffer pages */
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unsigned int page_count; /* number of current buffer pages */
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unsigned int finalized; /* buffer has been finalized */
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size_t *padding; /* padding counts per sub-buffer */
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size_t prev_padding; /* temporary variable */
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size_t bytes_consumed; /* bytes consumed in cur read subbuf */
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size_t early_bytes; /* bytes consumed before VFS inited */
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unsigned int cpu; /* this buf's cpu */
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} ____cacheline_aligned;
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/*
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* Relay channel data structure
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*/
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struct rchan
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{
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u32 version; /* the version of this struct */
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size_t subbuf_size; /* sub-buffer size */
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size_t n_subbufs; /* number of sub-buffers per buffer */
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size_t alloc_size; /* total buffer size allocated */
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struct rchan_callbacks *cb; /* client callbacks */
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struct kref kref; /* channel refcount */
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void *private_data; /* for user-defined data */
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size_t last_toobig; /* tried to log event > subbuf size */
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struct rchan_buf * __percpu *buf; /* per-cpu channel buffers */
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int is_global; /* One global buffer ? */
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struct list_head list; /* for channel list */
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struct dentry *parent; /* parent dentry passed to open */
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int has_base_filename; /* has a filename associated? */
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char base_filename[NAME_MAX]; /* saved base filename */
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};
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/*
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* Relay channel client callbacks
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*/
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struct rchan_callbacks
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{
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/*
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* subbuf_start - called on buffer-switch to a new sub-buffer
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* @buf: the channel buffer containing the new sub-buffer
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* @subbuf: the start of the new sub-buffer
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* @prev_subbuf: the start of the previous sub-buffer
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* @prev_padding: unused space at the end of previous sub-buffer
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*
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* The client should return 1 to continue logging, 0 to stop
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* logging.
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*
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* NOTE: subbuf_start will also be invoked when the buffer is
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* created, so that the first sub-buffer can be initialized
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* if necessary. In this case, prev_subbuf will be NULL.
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*
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* NOTE: the client can reserve bytes at the beginning of the new
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* sub-buffer by calling subbuf_start_reserve() in this callback.
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*/
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int (*subbuf_start) (struct rchan_buf *buf,
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void *subbuf,
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void *prev_subbuf,
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size_t prev_padding);
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/*
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* buf_mapped - relay buffer mmap notification
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* @buf: the channel buffer
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* @filp: relay file pointer
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*
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* Called when a relay file is successfully mmapped
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*/
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void (*buf_mapped)(struct rchan_buf *buf,
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struct file *filp);
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/*
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* buf_unmapped - relay buffer unmap notification
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* @buf: the channel buffer
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* @filp: relay file pointer
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*
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* Called when a relay file is successfully unmapped
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*/
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void (*buf_unmapped)(struct rchan_buf *buf,
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struct file *filp);
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/*
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* create_buf_file - create file to represent a relay channel buffer
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* @filename: the name of the file to create
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* @parent: the parent of the file to create
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* @mode: the mode of the file to create
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* @buf: the channel buffer
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* @is_global: outparam - set non-zero if the buffer should be global
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*
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* Called during relay_open(), once for each per-cpu buffer,
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* to allow the client to create a file to be used to
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* represent the corresponding channel buffer. If the file is
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* created outside of relay, the parent must also exist in
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* that filesystem.
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*
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* The callback should return the dentry of the file created
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* to represent the relay buffer.
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*
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* Setting the is_global outparam to a non-zero value will
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* cause relay_open() to create a single global buffer rather
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* than the default set of per-cpu buffers.
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*
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* See Documentation/filesystems/relay.txt for more info.
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*/
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struct dentry *(*create_buf_file)(const char *filename,
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struct dentry *parent,
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umode_t mode,
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struct rchan_buf *buf,
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int *is_global);
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/*
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* remove_buf_file - remove file representing a relay channel buffer
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* @dentry: the dentry of the file to remove
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*
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* Called during relay_close(), once for each per-cpu buffer,
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* to allow the client to remove a file used to represent a
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* channel buffer.
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*
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* The callback should return 0 if successful, negative if not.
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*/
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int (*remove_buf_file)(struct dentry *dentry);
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};
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/*
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* CONFIG_RELAY kernel API, kernel/relay.c
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*/
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struct rchan *relay_open(const char *base_filename,
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struct dentry *parent,
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size_t subbuf_size,
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size_t n_subbufs,
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struct rchan_callbacks *cb,
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void *private_data);
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extern int relay_late_setup_files(struct rchan *chan,
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const char *base_filename,
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struct dentry *parent);
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extern void relay_close(struct rchan *chan);
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extern void relay_flush(struct rchan *chan);
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extern void relay_subbufs_consumed(struct rchan *chan,
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unsigned int cpu,
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size_t consumed);
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extern void relay_reset(struct rchan *chan);
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extern int relay_buf_full(struct rchan_buf *buf);
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extern size_t relay_switch_subbuf(struct rchan_buf *buf,
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size_t length);
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/**
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* relay_write - write data into the channel
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* @chan: relay channel
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* @data: data to be written
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* @length: number of bytes to write
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*
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* Writes data into the current cpu's channel buffer.
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*
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* Protects the buffer by disabling interrupts. Use this
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* if you might be logging from interrupt context. Try
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* __relay_write() if you know you won't be logging from
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* interrupt context.
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*/
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static inline void relay_write(struct rchan *chan,
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const void *data,
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size_t length)
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{
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unsigned long flags;
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struct rchan_buf *buf;
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local_irq_save(flags);
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buf = *this_cpu_ptr(chan->buf);
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if (unlikely(buf->offset + length > chan->subbuf_size))
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length = relay_switch_subbuf(buf, length);
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memcpy(buf->data + buf->offset, data, length);
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buf->offset += length;
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local_irq_restore(flags);
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}
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/**
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* __relay_write - write data into the channel
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* @chan: relay channel
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* @data: data to be written
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* @length: number of bytes to write
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*
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* Writes data into the current cpu's channel buffer.
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*
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* Protects the buffer by disabling preemption. Use
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* relay_write() if you might be logging from interrupt
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* context.
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*/
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static inline void __relay_write(struct rchan *chan,
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const void *data,
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size_t length)
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{
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struct rchan_buf *buf;
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buf = *get_cpu_ptr(chan->buf);
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if (unlikely(buf->offset + length > buf->chan->subbuf_size))
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length = relay_switch_subbuf(buf, length);
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memcpy(buf->data + buf->offset, data, length);
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buf->offset += length;
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put_cpu_ptr(chan->buf);
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}
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/**
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* relay_reserve - reserve slot in channel buffer
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* @chan: relay channel
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* @length: number of bytes to reserve
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*
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* Returns pointer to reserved slot, NULL if full.
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*
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* Reserves a slot in the current cpu's channel buffer.
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* Does not protect the buffer at all - caller must provide
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* appropriate synchronization.
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*/
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static inline void *relay_reserve(struct rchan *chan, size_t length)
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{
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void *reserved = NULL;
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struct rchan_buf *buf = *get_cpu_ptr(chan->buf);
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if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
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length = relay_switch_subbuf(buf, length);
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if (!length)
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goto end;
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}
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reserved = buf->data + buf->offset;
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buf->offset += length;
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end:
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put_cpu_ptr(chan->buf);
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return reserved;
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}
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/**
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* subbuf_start_reserve - reserve bytes at the start of a sub-buffer
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* @buf: relay channel buffer
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* @length: number of bytes to reserve
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*
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* Helper function used to reserve bytes at the beginning of
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* a sub-buffer in the subbuf_start() callback.
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*/
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static inline void subbuf_start_reserve(struct rchan_buf *buf,
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size_t length)
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{
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BUG_ON(length >= buf->chan->subbuf_size - 1);
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buf->offset = length;
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}
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/*
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* exported relay file operations, kernel/relay.c
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*/
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extern const struct file_operations relay_file_operations;
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#ifdef CONFIG_RELAY
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int relay_prepare_cpu(unsigned int cpu);
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#else
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#define relay_prepare_cpu NULL
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#endif
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#endif /* _LINUX_RELAY_H */
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