diff options
author | Denis Vlasenko <vda.linux@googlemail.com> | 2007-08-13 01:33:06 +0400 |
---|---|---|
committer | Denis Vlasenko <vda.linux@googlemail.com> | 2007-08-13 01:33:06 +0400 |
commit | 5f1b149d541ebba7cab841cb647f113248f9fb8f (patch) | |
tree | e7f962fba89b6e201b4c857e32d85c9671b3db0d /sysklogd/logread.c | |
parent | 1b9064d5355b5c26676e8447a1900116066e42e4 (diff) |
syslogd,logread: get rid of head pointer, fix logread bug in the process
function old new delta
logread_main 450 462 +12
syslogd_main 1246 1252 +6
shbuf - 4 +4
buf 34 30 -4
packed_usage 22729 22724 -5
log_locally 957 767 -190
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 2/3 up/down: 22/-199) Total: -177 bytes
text data bss dec hex filename
773886 1116 11316 786318 bff8e busybox_old
773714 1116 11316 786146 bfee2 busybox_unstripped
Diffstat (limited to 'sysklogd/logread.c')
-rw-r--r-- | sysklogd/logread.c | 113 |
1 files changed, 69 insertions, 44 deletions
diff --git a/sysklogd/logread.c b/sysklogd/logread.c index ac354b5c3..597e285a5 100644 --- a/sysklogd/logread.c +++ b/sysklogd/logread.c @@ -19,11 +19,10 @@ enum { KEY_ID = 0x414e4547 }; /* "GENA" */ static struct shbuf_ds { - int32_t size; // size of data written - int32_t head; // start of message list + int32_t size; // size of data - 1 int32_t tail; // end of message list - char data[1]; // data/messages -} *buf; // shared memory pointer + char data[1]; // messages +} *shbuf; // Semaphore operation structures static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup @@ -34,7 +33,7 @@ static void error_exit(const char *str) ATTRIBUTE_NORETURN; static void error_exit(const char *str) { //release all acquired resources - shmdt(buf); + shmdt(shbuf); bb_perror_msg_and_die(str); } @@ -50,7 +49,7 @@ static void sem_up(int semid) static void interrupted(int sig ATTRIBUTE_UNUSED) { signal(SIGINT, SIG_IGN); - shmdt(buf); + shmdt(shbuf); exit(0); } @@ -66,79 +65,105 @@ int logread_main(int argc, char **argv) if (log_shmid == -1) bb_perror_msg_and_die("can't find syslogd buffer"); - // Attach shared memory to our char* - buf = shmat(log_shmid, NULL, SHM_RDONLY); - if (buf == NULL) + /* Attach shared memory to our char* */ + shbuf = shmat(log_shmid, NULL, SHM_RDONLY); + if (shbuf == NULL) bb_perror_msg_and_die("can't access syslogd buffer"); log_semid = semget(KEY_ID, 0, 0); if (log_semid == -1) error_exit("can't get access to semaphores for syslogd buffer"); - // attempt to redefine ^C signal signal(SIGINT, interrupted); - // Suppose atomic memory move - cur = follow ? buf->tail : buf->head; + /* Suppose atomic memory read */ + /* Max possible value for tail is shbuf->size - 1 */ + cur = shbuf->tail; + /* Loop for logread -f, one pass if there was no -f */ do { + unsigned shbuf_size; + unsigned shbuf_tail; + const char *shbuf_data; #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING - char *buf_data; - int log_len, j; + int i; + int len_first_part; + int len_total = len_total; /* for gcc */ + char *copy = copy; /* for gcc */ #endif if (semop(log_semid, SMrdn, 2) == -1) error_exit("semop[SMrdn]"); - if (DEBUG) - printf("head:%i cur:%d tail:%i size:%i\n", - buf->head, cur, buf->tail, buf->size); + /* Copy the info, helps gcc to realize that it doesn't change */ + shbuf_size = shbuf->size; + shbuf_tail = shbuf->tail; + shbuf_data = shbuf->data; /* pointer! */ - if (buf->head == buf->tail || cur == buf->tail) { - if (follow) { + if (DEBUG) + printf("cur:%d tail:%i size:%i\n", + cur, shbuf_tail, shbuf_size); + + if (!follow) { + /* advance to oldest complete message */ + /* find NUL */ + cur += strlen(shbuf_data + cur); + if (cur >= shbuf_size) { /* last byte in buffer? */ + cur = strnlen(shbuf_data, shbuf_tail); + if (cur == shbuf_tail) + goto unlock; /* no complete messages */ + } + /* advance to first byte of the message */ + cur++; + if (cur >= shbuf_size) /* last byte in buffer? */ + cur = 0; + } else { /* logread -f */ + if (cur == shbuf_tail) { sem_up(log_semid); fflush(stdout); sleep(1); /* TODO: replace me with a sleep_on */ continue; } - puts("<empty syslog>"); } - // Read Memory + /* Read from cur to tail */ #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING - log_len = buf->tail - cur; - if (log_len < 0) - log_len += buf->size; - buf_data = xmalloc(log_len); - - if (buf->tail >= cur) - j = log_len; - else - j = buf->size - cur; - memcpy(buf_data, buf->data + cur, j); - - if (buf->tail < cur) - memcpy(buf_data + buf->size - cur, buf->data, buf->tail); - cur = buf->tail; + len_first_part = len_total = shbuf_tail - cur; + if (len_total < 0) { + /* message wraps: */ + /* [SECOND PART.........FIRST PART] */ + /* ^data ^tail ^cur ^size */ + len_total += shbuf_size; + } + copy = xmalloc(len_total + 1); + if (len_first_part < 0) { + /* message wraps (see above) */ + len_first_part = shbuf_size - cur; + memcpy(copy + len_first_part, shbuf_data, shbuf_tail); + } + memcpy(copy, shbuf_data + cur, len_first_part); + copy[len_total] = '\0'; + cur = shbuf_tail; #else - while (cur != buf->tail) { - fputs(buf->data + cur, stdout); - cur += strlen(buf->data + cur) + 1; - if (cur >= buf->size) + while (cur != shbuf_tail) { + fputs(shbuf_data + cur, stdout); + cur += strlen(shbuf_data + cur) + 1; + if (cur >= shbuf_size) cur = 0; } #endif - // release the lock on the log chain + unlock: + /* release the lock on the log chain */ sem_up(log_semid); #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING - for (j = 0; j < log_len; j += strlen(buf_data+j) + 1) { - fputs(buf_data + j, stdout); + for (i = 0; i < len_total; i += strlen(copy + i) + 1) { + fputs(copy + i, stdout); } - free(buf_data); + free(copy); #endif } while (follow); - shmdt(buf); + shmdt(shbuf); fflush_stdout_and_exit(EXIT_SUCCESS); } |