Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk v3 05/40] printk: fix setting first seq for consoles | Date | Mon, 7 Nov 2022 15:22:03 +0106 |
| |
It used to be that all consoles were synchronized with respect to which message they were printing. After commit a699449bb13b ("printk: refactor and rework printing logic"), all consoles have their own @seq for tracking which message they are on. That commit also changed how the initial sequence number was chosen. Instead of choosing the next non-printed message, it chose the sequence number of the next message that will be added to the ringbuffer.
That change created a possibility that a non-boot console taking over for a boot console might skip messages if the boot console was behind and did not have a chance to catch up before being unregistered.
Since it is not possible to know which boot console a console is taking over, use the lowest @seq of all the enabled boot consoles. If no boot consoles are available/enabled, begin with the next message that will be added to the ringbuffer.
Also, since boot consoles are meant to be used at boot time, handle them the same as CON_PRINTBUFFER to ensure that no initial messages are skipped.
Signed-off-by: John Ogness <john.ogness@linutronix.de> --- kernel/printk/printk.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 173f46a29252..8974523f3107 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3222,14 +3222,26 @@ void register_console(struct console *newcon) } newcon->dropped = 0; - if (newcon->flags & CON_PRINTBUFFER) { + if (newcon->flags & (CON_PRINTBUFFER | CON_BOOT)) { /* Get a consistent copy of @syslog_seq. */ mutex_lock(&syslog_lock); newcon->seq = syslog_seq; mutex_unlock(&syslog_lock); } else { - /* Begin with next message. */ + /* Begin with next message added to ringbuffer. */ newcon->seq = prb_next_seq(prb); + + /* + * If an enabled boot console is not caught up, start with + * that message instead. That boot console will be + * unregistered shortly and may be the same device. + */ + for_each_console(con) { + if ((con->flags & (CON_BOOT | CON_ENABLED)) == (CON_BOOT | CON_ENABLED) && + con->seq < newcon->seq) { + newcon->seq = con->seq; + } + } } /* -- 2.30.2
| |