@@ -150,7 +150,7 @@ static int console_may_schedule;
* are stored..
*
* If the heads indicate available messages, the length in the header
- * tells the start next message. A length == 0 for the next message
+ * tells the start of the next message. A length == 0 for the next message
* indicates a wrap-around to the beginning of the buffer.
*
* Every record carries the monotonic timestamp in microseconds, as well as
@@ -159,6 +159,17 @@ static int console_may_schedule;
* a matching syslog facility, by default LOG_USER. The origin of every
* message can be reliably determined that way.
*
+ * If a printk() call doesn't end in a newline, the content of the message
+ * is buffered temporarily so that a subsequent printk() call can be
+ * appended to it. Occasionally a buffered/partial message needs to be
+ * flushed to the log before the logically next printk() call is seen.
+ * This is distinguished in log records by the presence (or absence) of a
+ * LOG_COMPLETE flag. In this case the last log record comprising a
+ * the original message has LOG_COMPLETE set; the rest do not. When
+ * formatted, a log record will include a prefix (including a time stamp
+ * and possibly a syslog value) whenever its predecessor in the log was
+ * marked LOG_COMPLETE.
+ *
* The human readable log message directly follows the message header. The
* length of the message text is stored in the header, the stored message
* is not terminated.
@@ -209,7 +220,7 @@ static int console_may_schedule;
enum log_flags {
LOG_NOCONS = 1, /* already flushed, do not print to console */
- LOG_NEWLINE = 2, /* text ended with a newline */
+ LOG_COMPLETE = 2, /* this record ends a log entry */
};
struct printk_log {
@@ -432,7 +443,7 @@ static int log_store(int facility, int level, bool force_new,
* the previous one to mark it complete.
*/
if (force_new && log_last_msg)
- log_last_msg->flags |= LOG_NEWLINE;
+ log_last_msg->flags |= LOG_COMPLETE;
msg = (struct printk_log *)(log_buf + log_next_idx);
memcpy(log_text(msg), text, text_len);
@@ -632,9 +643,9 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
* a record that should be merged with one or more earlier records.
* And a '-' indicates a "normal" self-contained single record.
*/
- if (!(user->prev & LOG_NEWLINE))
+ if (!(user->prev & LOG_COMPLETE))
cont = '+';
- else if (!(msg->flags & LOG_NEWLINE))
+ else if (!(msg->flags & LOG_COMPLETE))
cont = 'c';
else
cont = '-';
@@ -1015,15 +1026,9 @@ static size_t msg_print_text(const struct printk_log *msg, enum log_flags prev,
{
const char *text = log_text(msg);
size_t text_size = msg->text_len;
- bool prefix = true;
- bool newline = true;
size_t len = 0;
-
- if (!(prev & LOG_NEWLINE))
- prefix = false;
-
- if (!(msg->flags & LOG_NEWLINE))
- newline = false;
+ bool prefix = !!(prev & LOG_COMPLETE);
+ bool newline = !!(msg->flags & LOG_COMPLETE);
do {
const char *next = memchr(text, '\n', text_size);
@@ -1556,7 +1561,8 @@ static size_t cont_print_text(char *text, size_t size)
size_t textlen = 0;
size_t len;
- if (cont.cons == 0 && (console_prev & LOG_NEWLINE)) {
+ /* If we're starting a new one, format a time stamp */
+ if (cont.cons == 0 && console_prev & LOG_COMPLETE) {
textlen += print_time(cont.ts_nsec, text);
size -= textlen;
}
@@ -1571,7 +1577,7 @@ static size_t cont_print_text(char *text, size_t size)
}
if (cont.flushed) {
- if (cont.flags & LOG_NEWLINE)
+ if (cont.flags & LOG_COMPLETE)
text[textlen++] = '\n';
/* got everything, release buffer */
cont.len = 0;
@@ -1637,7 +1643,7 @@ asmlinkage int vprintk_emit(int facility, int level,
recursion_bug = 0;
text_len = strlen(recursion_msg);
/* emit KERN_CRIT message */
- printed_len += log_store(0, 2, true, LOG_NEWLINE, 0,
+ printed_len += log_store(0, 2, true, LOG_COMPLETE, 0,
NULL, 0, recursion_msg, text_len);
}
@@ -1659,7 +1665,7 @@ asmlinkage int vprintk_emit(int facility, int level,
*/
if (text_len && text[text_len-1] == '\n') {
text_len--;
- lflags = LOG_NEWLINE;
+ lflags = LOG_COMPLETE;
}
/* strip kernel syslog prefix and extract log level or control flags */
@@ -1690,17 +1696,23 @@ asmlinkage int vprintk_emit(int facility, int level,
if (dict) {
force_new = true;
- lflags = LOG_NEWLINE;
+ lflags = LOG_COMPLETE;
}
- if (!(lflags & LOG_NEWLINE)) {
+ /*
+ * If there's a partial record buffered by someone else
+ * we'll want to force a new entry to be started.
+ */
+ if (cont.len)
+ force_new |= cont.owner != current;
+ if (!(lflags & LOG_COMPLETE)) {
/*
* We're recording an incomplete record. We'll add it to the
- * "cont" buffer if possible, but if it contains data written
- * by somebody else we need to flush that to the log first.
+ * "cont" buffer if possible, but if we're forcing a new
+ * entry we need to flush the buffer to the log first.
*/
- if (cont.len && (force_new || cont.owner != current))
- cont_flush(LOG_NEWLINE);
+ if (cont.len && force_new)
+ cont_flush(LOG_COMPLETE);
/* If we're unable to buffer it, store it immediately */
if (cont_add(facility, level, text, text_len))
@@ -1713,18 +1725,17 @@ asmlinkage int vprintk_emit(int facility, int level,
bool stored = false;
/*
- * This record is complete (it should be formatted with a
- * newline), so we'll be writing it to the log. If there
- * are any incomplete records buffered we will need to
- * flush those to the log first. If possible, we'll add
- * this record to the buffer first. If there's nothing
- * buffered, just write this record to the log.
+ * This record is complete, so we'll be writing it to the log.
+ * If there are any incomplete records buffered we'll try to
+ * add this record to the buffer before flushing it to the log.
+ * Otherwise if there's nothing buffered, just write this
+ * record to the log directly.
*/
if (cont.len) {
- if (cont.owner == current && !force_new)
+ if (!force_new)
stored = cont_add(facility, level, text,
text_len);
- cont_flush(LOG_NEWLINE);
+ cont_flush(LOG_COMPLETE);
}
if (stored)
Rename LOG_NEWLINE to be LOG_COMPLETE, so it makes more sense in the context of a log record (or a string of them) rather than how a record gets formatted. Add a block of commentary explaining how the log flags indicate that consecutive log records should be treated as a single logical log entry. Do some other tidying of the code now that a lot of the former flags complexity has been eliminated. Signed-off-by: Alex Elder <elder@linaro.org> --- kernel/printk/printk.c | 73 +++++++++++++++++++++++++++++--------------------- 1 file changed, 42 insertions(+), 31 deletions(-)