X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=libustconsumer%2Flowlevel.c;fp=libustconsumer%2Flowlevel.c;h=7eb124b98d75263c6aef91e1b0ee98ac8c928bcc;hb=9dc7b7ff797a5cbb1e9ffd59e053a04562f306c4;hp=0000000000000000000000000000000000000000;hpb=28c1bb4003ca120888a1d61d5ec71eac426ae490;p=ust.git diff --git a/libustconsumer/lowlevel.c b/libustconsumer/lowlevel.c new file mode 100644 index 0000000..7eb124b --- /dev/null +++ b/libustconsumer/lowlevel.c @@ -0,0 +1,143 @@ +/* Copyright (C) 2009 Pierre-Marc Fournier + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include +#include +#include + +#include "ust/ustconsumer.h" +#include "buffers.h" +#include "tracer.h" +#include "usterr.h" + +/* This truncates to an offset in the buffer. */ +#define USTD_BUFFER_TRUNC(offset, bufinfo) \ + ((offset) & (~(((bufinfo)->subbuf_size*(bufinfo)->n_subbufs)-1))) + +#define LTT_MAGIC_NUMBER 0x00D6B7ED +#define LTT_REV_MAGIC_NUMBER 0xEDB7D600 + +/* Returns the size of a subbuffer size. This is the size that + * will need to be written to disk. + * + * @subbuffer: pointer to the beginning of the subbuffer (the + * beginning of its header) + */ + +size_t subbuffer_data_size(void *subbuf) +{ + struct ltt_subbuffer_header *header = subbuf; + int reverse; + u32 data_size; + + if(header->magic_number == LTT_MAGIC_NUMBER) { + reverse = 0; + } + else if(header->magic_number == LTT_REV_MAGIC_NUMBER) { + reverse = 1; + } + else { + return -1; + } + + data_size = header->sb_size; + if(reverse) + data_size = bswap_32(data_size); + + return data_size; +} + + +void finish_consuming_dead_subbuffer(struct ustconsumer_callbacks *callbacks, struct buffer_info *buf) +{ + struct ust_buffer *ustbuf = buf->bufstruct_mem; + + long write_offset = uatomic_read(&ustbuf->offset); + long consumed_offset = uatomic_read(&ustbuf->consumed); + + long i_subbuf; + + DBG("processing dead buffer (%s)", buf->name); + DBG("consumed offset is %ld (%s)", consumed_offset, buf->name); + DBG("write offset is %ld (%s)", write_offset, buf->name); + + /* First subbuf that we need to consume now. It is not modulo'd. + * Consumed_offset is the next byte to consume. */ + long first_subbuf = consumed_offset / buf->subbuf_size; + /* Last subbuf that we need to consume now. It is not modulo'd. + * Write_offset is the next place to write so write_offset-1 is the + * last place written. */ + long last_subbuf = (write_offset - 1) / buf->subbuf_size; + + DBG("first_subbuf=%ld", first_subbuf); + DBG("last_subbuf=%ld", last_subbuf); + + if(last_subbuf - first_subbuf >= buf->n_subbufs) { + DBG("an overflow has occurred, nothing can be recovered"); + return; + } + + /* Iterate on subbuffers to recover. */ + for(i_subbuf = first_subbuf % buf->n_subbufs; ; i_subbuf++, i_subbuf %= buf->n_subbufs) { + /* commit_seq is the offset in the buffer of the end of the last sequential commit. + * Bytes beyond this limit cannot be recovered. This is a free-running counter. */ + long commit_seq = uatomic_read(&ustbuf->commit_seq[i_subbuf]); + + unsigned long valid_length = buf->subbuf_size; + long n_subbufs_order = get_count_order(buf->n_subbufs); + long commit_seq_mask = (~0UL >> n_subbufs_order); + + struct ltt_subbuffer_header *header = (struct ltt_subbuffer_header *)((char *)buf->mem+i_subbuf*buf->subbuf_size); + + if((commit_seq & commit_seq_mask) == 0) { + /* There is nothing to do. */ + /* FIXME: is this needed? */ + break; + } + + /* Check if subbuf was fully written. This is from Mathieu's algorithm/paper. */ + /* FIXME: not sure data_size = 0xffffffff when the buffer is not full. It might + * take the value of the header size initially */ + if (((commit_seq - buf->subbuf_size) & commit_seq_mask) + - (USTD_BUFFER_TRUNC(consumed_offset, buf) >> n_subbufs_order) == 0 + && header->data_size != 0xffffffff && header->sb_size != 0xffffffff) { + /* If it was, we only check the data_size. This is the amount of valid data at + * the beginning of the subbuffer. */ + valid_length = header->data_size; + DBG("writing full subbuffer (%d) with valid_length = %ld", i_subbuf, valid_length); + } + else { + /* If the subbuffer was not fully written, then we don't check data_size because + * it hasn't been written yet. Instead we check commit_seq and use it to choose + * a value for data_size. The viewer will need this value when parsing. + */ + + valid_length = commit_seq & (buf->subbuf_size-1); + DBG("writing unfull subbuffer (%d) with valid_length = %ld", i_subbuf, valid_length); + header->data_size = valid_length; + header->sb_size = PAGE_ALIGN(valid_length); + assert(i_subbuf == (last_subbuf % buf->n_subbufs)); + } + + if(callbacks->on_read_partial_subbuffer) + callbacks->on_read_partial_subbuffer(callbacks, buf, i_subbuf, valid_length); + + if(i_subbuf == last_subbuf % buf->n_subbufs) + break; + } +} +