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 <[email protected]> --- kernel/printk/printk.c | 73 +++++++++++++++++++++++++++++--------------------- 1 file changed, 42 insertions(+), 31 deletions(-) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index bfc2581..69bfd39 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -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) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
