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Date: Sun, 13 May 2012 23:30:46 +0200
From: Kay Sievers <kay@...y.org>
To: Sasha Levin <levinsasha928@...il.com>
Cc: Greg Kroah-Hartmann <greg@...ah.com>,
Yinghai Lu <yinghai@...nel.org>, Joe Perches <joe@...ches.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 1/3] printk: convert byte-buffer to
variable-length record buffer
On Fri, 2012-05-11 at 12:35 +0200, Sasha Levin wrote:
> On Thu, May 10, 2012 at 4:30 AM, Kay Sievers <kay@...y.org> wrote:
> > On Wed, 2012-05-09 at 16:06 -0700, Greg Kroah-Hartmann wrote:
> >> On Wed, May 09, 2012 at 04:02:40PM -0700, Yinghai Lu wrote:
> >> > On Wed, May 9, 2012 at 7:37 AM, Kay Sievers <kay@...y.org> wrote:
> >> > >
> >> > >> Changing printk semantics and trying to stabilize
> >> > >> printk message content are bad ideas though.
> >> > >
> >> > > Again, nobody talks about content of here.
> >> >
> >> > printk_time=1 does not work anymore with this patch on serial console.
> >>
> >> Known issue, I think Kay is working on the solution for this right
> >> now...
> >
> > Sure, and this seems to work for me.
> >
> > Thanks,
> > Kay
> >
> >
> > From: Kay Sievers <kay@...y.org>
> > Subject: printk() - restore timestamp printing at console output
> >
> > The output of the timestamps got lost with the conversion of the
> > kmsg buffer to records; restore the old behavior.
> >
> > Document, that CONFIG_PRINTK_TIME now only controls the output of
> > the timestamps in the syslog() system call and on the console, and
> > not the recording of the timestamps.
> >
> > Signed-off-by: Kay Sievers <kay@...y.org>
> > ---
>
> This has a small issue with the way timing is printed compared to how
> it worked previously.
>
> Consider the following case:
>
> printk("\n foo \n bar \n zoot")
>
> Previously, you would see timing on each line of the print, but now
> you see it only on the first.
Does this fix it for you? It should fully restore the current behavior
for multi-line printing.
Thanks,
Kay
From: Kay Sievers <kay@...y.org>
Subject: printk() - restore prefix/timestamp printing for multi-newline strings
Calls like:
printk("\n *** DEADLOCK ***\n\n");
will print 3 properly indented, separated, syslog + timestamp prefixed lines in
the log output.
Reported-By: Sasha Levin <levinsasha928@...il.com>
Signed-off-by: Kay Sievers <kay@...y.org>
---
printk.c | 127 +++++++++++++++++++++++++++++++++++++--------------------------
1 file changed, 76 insertions(+), 51 deletions(-)
diff --git a/kernel/printk.c b/kernel/printk.c
index c42faf9..ee312c7 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -448,7 +448,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
/* escape non-printable characters */
for (i = 0; i < msg->text_len; i++) {
- char c = log_text(msg)[i];
+ unsigned char c = log_text(msg)[i];
if (c < ' ' || c >= 128)
len += sprintf(user->buf + len, "\\x%02x", c);
@@ -461,7 +461,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf,
bool line = true;
for (i = 0; i < msg->dict_len; i++) {
- char c = log_dict(msg)[i];
+ unsigned char c = log_dict(msg)[i];
if (line) {
user->buf[len++] = ' ';
@@ -785,56 +791,81 @@ static bool printk_time;
#endif
module_param_named(time, printk_time, bool, S_IRUGO | S_IWUSR);
-static size_t prepend_timestamp(unsigned long long t, char *buf)
+static size_t print_prefix(const struct log *msg, bool syslog, char *buf)
{
- unsigned long rem_ns;
+ size_t len = 0;
- if (!printk_time)
- return 0;
+ if (syslog) {
+ if (buf) {
+ len += sprintf(buf, "<%u>", msg->level);
+ } else {
+ len += 3;
+ if (msg->level > 9)
+ len++;
+ if (msg->level > 99)
+ len++;
+ }
+ }
- if (!buf)
- return 15;
+ if (printk_time) {
+ if (buf) {
+ unsigned long long ts = msg->ts_nsec;
+ unsigned long rem_nsec = do_div(ts, 1000000000);
- rem_ns = do_div(t, 1000000000);
+ len += sprintf(buf + len, "[%5lu.%06lu] ",
+ (unsigned long) ts, rem_nsec / 1000);
+ } else {
+ len += 15;
+ }
+ }
- return sprintf(buf, "[%5lu.%06lu] ",
- (unsigned long) t, rem_ns / 1000);
+ return len;
}
-static int syslog_print_line(u32 idx, char *text, size_t size)
+static size_t msg_print_text(const struct log *msg, bool syslog,
+ char *buf, size_t size)
{
- struct log *msg;
- size_t len;
+ const char *text = log_text(msg);
+ size_t text_size = msg->text_len;
+ size_t len = 0;
- msg = log_from_idx(idx);
- if (!text) {
- /* calculate length only */
- len = 3;
+ do {
+ const char *next = memchr(text, '\n', text_size);
+ size_t text_len;
- if (msg->level > 9)
- len++;
- if (msg->level > 99)
- len++;
- len += prepend_timestamp(0, NULL);
+ if (next) {
+ text_len = next - text;
+ next++;
+ text_size -= next - text;
+ } else {
+ text_len = text_size;
+ }
- len += msg->text_len;
- len++;
- return len;
- }
+ if (buf) {
+ if (print_prefix(msg, syslog, NULL) +
+ text_len + 1>= size - len)
+ break;
+
+ len += print_prefix(msg, syslog, buf + len);
+ memcpy(buf + len, text, text_len);
+ len += text_len;
+ buf[len++] = '\n';
+ } else {
+ /* SYSLOG_ACTION_* buffer size only calculation */
+ len += print_prefix(msg, syslog, NULL);
+ len += text_len + 1;
+ }
+
+ text = next;
+ } while (text);
- len = sprintf(text, "<%u>", msg->level);
- len += prepend_timestamp(msg->ts_nsec, text + len);
- if (len + msg->text_len > size)
- return -EINVAL;
- memcpy(text + len, log_text(msg), msg->text_len);
- len += msg->text_len;
- text[len++] = '\n';
return len;
}
static int syslog_print(char __user *buf, int size)
{
char *text;
+ struct log *msg;
int len;
text = kmalloc(LOG_LINE_MAX, GFP_KERNEL);
@@ -847,7 +878,8 @@ static int syslog_print(char __user *buf, int size)
syslog_seq = log_first_seq;
syslog_idx = log_first_idx;
}
- len = syslog_print_line(syslog_idx, text, LOG_LINE_MAX);
+ msg = log_from_idx(syslog_idx);
+ len = msg_print_text(msg, true, text, LOG_LINE_MAX);
syslog_idx = log_next(syslog_idx);
syslog_seq++;
raw_spin_unlock_irq(&logbuf_lock);
@@ -887,14 +919,18 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
seq = clear_seq;
idx = clear_idx;
while (seq < log_next_seq) {
- len += syslog_print_line(idx, NULL, 0);
+ struct log *msg = log_from_idx(idx);
+
+ len += msg_print_text(msg, true, NULL, 0);
idx = log_next(idx);
seq++;
}
seq = clear_seq;
idx = clear_idx;
while (len > size && seq < log_next_seq) {
- len -= syslog_print_line(idx, NULL, 0);
+ struct log *msg = log_from_idx(idx);
+
+ len -= msg_print_text(msg, true, NULL, 0);
idx = log_next(idx);
seq++;
}
@@ -904,9 +940,10 @@ static int syslog_print_all(char __user *buf, int size, bool clear)
len = 0;
while (len >= 0 && seq < next_seq) {
+ struct log *msg = log_from_idx(idx);
int textlen;
- textlen = syslog_print_line(idx, text, LOG_LINE_MAX);
+ textlen = msg_print_text(msg, true, text, LOG_LINE_MAX);
if (textlen < 0) {
len = textlen;
break;
@@ -1044,7 +1081,9 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
seq = syslog_seq;
idx = syslog_idx;
while (seq < log_next_seq) {
- error += syslog_print_line(idx, NULL, 0);
+ struct log *msg = log_from_idx(idx);
+
+ error += msg_print_text(msg, true, NULL, 0);
idx = log_next(idx);
seq++;
}
@@ -1439,10 +1478,8 @@ static struct log *log_from_idx(u32 idx) { return NULL; }
static u32 log_next(u32 idx) { return 0; }
static char *log_text(const struct log *msg) { return NULL; }
static void call_console_drivers(int level, const char *text, size_t len) {}
-static size_t prepend_timestamp(unsigned long long t, char *buf)
-{
- return 0;
-}
+static size_t msg_print_text(const struct log *msg, bool syslog,
+ char *buf, size_t size) { return 0; }
#endif /* CONFIG_PRINTK */
@@ -1750,7 +1787,7 @@ again:
for (;;) {
struct log *msg;
static char text[LOG_LINE_MAX];
- size_t len, l;
+ size_t len;
int level;
raw_spin_lock_irqsave(&logbuf_lock, flags);
@@ -1771,13 +1808,7 @@ again:
msg = log_from_idx(console_idx);
level = msg->level & 7;
- len = prepend_timestamp(msg->ts_nsec, text);
- l = msg->text_len;
- if (len + l + 1 >= sizeof(text))
- l = sizeof(text) - len - 1;
- memcpy(text + len, log_text(msg), l);
- len += l;
- text[len++] = '\n';
+ len = msg_print_text(msg, false, text, sizeof(text));
console_idx = log_next(console_idx);
console_seq++;
--
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