brain-hackers_pepepper-mirror/linux-brain
1
0
Fork 0
mirror of https://github.com/brain-hackers/linux-brain.git synced 2024-06-09 23:36:23 +09:00
Code Issues Projects Releases Wiki Activity

printk: keep kernel cont support always enabled

Browse Source 
Since commit 5c2992ee7f ("printk: remove console flushing special
cases for partial buffered lines") we don't print cont fragments
to the consoles; cont lines are now proper log_buf entries and
there is no "consecutive continuation flag" anymore: we either
have 'c' entries that mark continuation lines without fragments;
or '-' entries that mark normal logbuf entries. There are no '+'
entries anymore.

However, we still have a small leftover - presence of ext_console
drivers disables kernel cont support and we flush each pr_cont()
and store it as a separate log_buf entry. Previously, it worked
because msg_print_ext_header() had that "an optional external merge
of the records" functionality:

	if (msg->flags & LOG_CONT)
		cont = (prev_flags & LOG_CONT) ? '+' : 'c';

We don't do this as of now, so keep kernel cont always enabled.

Note from pmladek:

The original purpose was to get full information including
the metadata and dictionary via extended console drivers,
see commit 6fe29354be ("printk: implement support
for extended console drivers").

The dictionary probably was the most important part but
it was actually lost:

  static void cont_flush(void)
  {
  [...]
	log_store(cont.facility, cont.level, cont.flags, cont.ts_nsec,
		  NULL, 0, cont.buf, cont.len);

Nobody noticed because the only dictionary user is dev_printk()
and dev_cont() is _not_ defined.

Link: http://lkml.kernel.org/r/20181002023836.4487-2-sergey.senozhatsky@gmail.com
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dmitriy Vyukov <dvyukov@google.com>
Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
[pmladek@suse.com: Updated commit message]
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
Sergey Senozhatsky 2018-10-02 11:38:34 +09:00 committed by Petr Mladek
parent e6fe3e5b7d
commit 9627808d2d
1 changed files with 4 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
kernel/printk/printk.c
View File

@ -194,16 +194,7 @@ int devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write,
return 0;
}
/*
* Number of registered extended console drivers.
*
* If extended consoles are present, in-kernel cont reassembly is disabled
* and each fragment is stored as a separate log entry with proper
* continuation flag so that every emitted message has full metadata. This
* doesn't change the result for regular consoles or /proc/kmsg. For
* /dev/kmsg, as long as the reader concatenates messages according to
* consecutive continuation flags, the end result should be the same too.
*/
/* Number of registered extended console drivers. */
static int nr_ext_console_drivers;
/*
@ -1781,12 +1772,8 @@ static void cont_flush(void)
static bool cont_add(int facility, int level, enum log_flags flags, const char *text, size_t len)
{
/*
* If ext consoles are present, flush and skip in-kernel
* continuation. See nr_ext_console_drivers definition. Also, if
* the line gets too long, split it up in separate records.
*/
if (nr_ext_console_drivers || cont.len + len > sizeof(cont.buf)) {
/* If the line gets too long, split it up in separate records. */
if (cont.len + len > sizeof(cont.buf)) {
cont_flush();
return false;
}
@ -2706,8 +2693,7 @@ void register_console(struct console *newcon)
}
if (newcon->flags & CON_EXTENDED)
if (!nr_ext_console_drivers++)
pr_info("continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n");
nr_ext_console_drivers++;
if (newcon->flags & CON_PRINTBUFFER) {
/*