--- /dev/null
+/* 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 <stdlib.h>
+#include <assert.h>
+#include <byteswap.h>
+
+#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;
+ }
+}
+
projects / ust.git / blobdiff