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Subject[RFC PATCH v1 13/25] printk: track seq per console
Date
Allow each console to track which seq record was last printed. This
simplifies identifying dropped records.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
include/linux/console.h | 1 +
kernel/printk/printk.c | 30 +++++++++++++++++++++++++++---
2 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/include/linux/console.h b/include/linux/console.h
index ec9bdb3d7bab..7fa06a058339 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -153,6 +153,7 @@ struct console {
short flags;
short index;
int cflag;
+ unsigned long printk_seq;
void *data;
struct console *next;
};
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index ece54c24ea0d..ebd9aac06323 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1453,6 +1453,16 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
return do_syslog(type, buf, len, SYSLOG_FROM_READER);
}

+static void print_console_dropped(struct console *con, u64 count)
+{
+ char text[64];
+ int len;
+
+ len = sprintf(text, "** %llu printk message%s dropped **\n",
+ count, count > 1 ? "s" : "");
+ con->write(con, text, len);
+}
+
static void format_text(struct printk_log *msg, u64 seq,
char *ext_text, size_t *ext_len,
char *text, size_t *len, bool time)
@@ -1486,7 +1496,7 @@ static void format_text(struct printk_log *msg, u64 seq,
* log_buf[start] to log_buf[end - 1].
* The console_lock must be held.
*/
-static void call_console_drivers(const char *ext_text, size_t ext_len,
+static void call_console_drivers(u64 seq, const char *ext_text, size_t ext_len,
const char *text, size_t len)
{
struct console *con;
@@ -1504,6 +1514,19 @@ static void call_console_drivers(const char *ext_text, size_t ext_len,
if (!cpu_online(raw_smp_processor_id()) &&
!(con->flags & CON_ANYTIME))
continue;
+ if (con->printk_seq >= seq)
+ continue;
+
+ con->printk_seq++;
+ if (con->printk_seq < seq) {
+ print_console_dropped(con, seq - con->printk_seq);
+ con->printk_seq = seq;
+ }
+
+ /* for supressed messages, only seq is updated */
+ if (len == 0 && ext_len == 0)
+ continue;
+
if (con->flags & CON_EXTENDED)
con->write(con, ext_text, ext_len);
else
@@ -1738,7 +1761,7 @@ static ssize_t msg_print_ext_header(char *buf, size_t size,
static ssize_t msg_print_ext_body(char *buf, size_t size,
char *dict, size_t dict_len,
char *text, size_t text_len) { return 0; }
-static void call_console_drivers(const char *ext_text, size_t ext_len,
+static void call_console_drivers(u64 seq, const char *ext_text, size_t ext_len,
const char *text, size_t len) {}
static size_t msg_print_text(const struct printk_log *msg, bool syslog,
bool time, char *buf, size_t size) { return 0; }
@@ -2481,8 +2504,9 @@ static int printk_kthread_func(void *data)
&len, printk_time);

console_lock();
+ call_console_drivers(master_seq, ext_text,
+ ext_len, text, len);
if (len > 0 || ext_len > 0) {
- call_console_drivers(ext_text, ext_len, text, len);
boot_delay_msec(msg->level);
printk_delay();
}
--
2.11.0
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