1 /* Copyright (C) 2009 Pierre-Marc Fournier
3 * This library is free software; you can redistribute it and/or
4 * modify it under the terms of the GNU Lesser General Public
5 * License as published by the Free Software Foundation; either
6 * version 2.1 of the License, or (at your option) any later version.
8 * This library is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * Lesser General Public License for more details.
13 * You should have received a copy of the GNU Lesser General Public
14 * License along with this library; if not, write to the Free Software
15 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 #include <ust/tracer.h>
24 /* This truncates to an offset in the buffer. */
25 #define USTD_BUFFER_TRUNC(offset, bufinfo) \
26 ((offset) & (~(((bufinfo)->subbuf_size*(bufinfo)->n_subbufs)-1)))
28 void finish_consuming_dead_subbuffer(struct buffer_info
*buf
)
30 struct ltt_channel_buf_struct
*ltt_buf
= buf
->bufstruct_mem
;
32 long write_offset
= local_read(<t_buf
->offset
);
33 long consumed_offset
= atomic_long_read(<t_buf
->consumed
);
37 DBG("processing died buffer");
38 DBG("consumed offset is %ld", consumed_offset
);
39 DBG("write offset is %ld", write_offset
);
41 /* First subbuf that we need to consume now. It is not modulo'd.
42 * Consumed_offset is the next byte to consume. */
43 long first_subbuf
= consumed_offset
/ buf
->subbuf_size
;
44 /* Last subbuf that we need to consume now. It is not modulo'd.
45 * Write_offset is the next place to write so write_offset-1 is the
46 * last place written. */
47 long last_subbuf
= (write_offset
- 1) / buf
->subbuf_size
;
49 DBG("first_subbuf=%ld", first_subbuf
);
50 DBG("last_subbuf=%ld", last_subbuf
);
52 if(last_subbuf
- first_subbuf
>= buf
->n_subbufs
) {
53 DBG("an overflow has occurred, nothing can be recovered");
57 /* Iterate on subbuffers to recover. */
58 for(i_subbuf
=first_subbuf
; ; i_subbuf
++, i_subbuf
%= buf
->n_subbufs
) {
60 /* commit_seq is the offset in the buffer of the end of the last sequential commit.
61 * Bytes beyond this limit cannot be recovered. This is a free-running counter. */
62 long commit_seq
= local_read(<t_buf
->commit_seq
[i_subbuf
]);
64 unsigned long valid_length
= buf
->subbuf_size
;
65 long n_subbufs_order
= get_count_order(buf
->n_subbufs
);
66 long commit_seq_mask
= (~0UL >> n_subbufs_order
);
68 struct ltt_subbuffer_header
*header
= (struct ltt_subbuffer_header
*)((char *)buf
->mem
+i_subbuf
*buf
->subbuf_size
);
70 if((commit_seq
& commit_seq_mask
) == 0) {
71 /* There is nothing to do. */
72 /* FIXME: is this needed? */
76 /* Check if subbuf was fully written. This is from Mathieu's algorithm/paper. */
77 if (((commit_seq
- buf
->subbuf_size
) & commit_seq_mask
)
78 - (USTD_BUFFER_TRUNC(consumed_offset
, buf
) >> n_subbufs_order
)
80 /* If it was, we only check the lost_size. This is the lost padding at the end of
82 valid_length
= (unsigned long)buf
->subbuf_size
- header
->lost_size
;
85 /* If the subbuffer was not fully written, then we don't check lost_size because
86 * it hasn't been written yet. Instead we check commit_seq and use it to choose
87 * a value for lost_size. The viewer will need this value when parsing.
90 valid_length
= commit_seq
& (buf
->subbuf_size
-1);
91 header
->lost_size
= buf
->subbuf_size
-valid_length
;
92 assert(i_subbuf
== (last_subbuf
% buf
->n_subbufs
));
96 patient_write(buf
->file_fd
, buf
->mem
+ i_subbuf
* buf
->subbuf_size
, valid_length
);
98 /* pad with empty bytes */
99 tmp
= malloc(buf
->subbuf_size
-valid_length
);
100 memset(tmp
, 0, buf
->subbuf_size
-valid_length
);
101 patient_write(buf
->file_fd
, tmp
, buf
->subbuf_size
-valid_length
);
104 if(i_subbuf
== last_subbuf
% buf
->n_subbufs
)
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