From 9627808d2d409279cea3fb334212d04a83ff6371 Mon Sep 17 00:00:00 2001 From: Sergey Senozhatsky Date: Tue, 2 Oct 2018 11:38:34 +0900 Subject: printk: keep kernel cont support always enabled Since commit 5c2992ee7fd8a29 ("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 6fe29354befe4c46e ("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 Cc: Andrew Morton Cc: Dmitriy Vyukov Cc: Tetsuo Handa Cc: Tejun Heo Cc: Peter Zijlstra Cc: LKML Cc: Sergey Senozhatsky Signed-off-by: Sergey Senozhatsky [pmladek@suse.com: Updated commit message] Signed-off-by: Petr Mladek --- kernel/printk/printk.c | 22 ++++------------------ 1 file changed, 4 insertions(+), 18 deletions(-) (limited to 'kernel/printk') diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index fce696d80e09..f717656c0fac 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -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) { /* -- cgit v1.2.3