commit 84b5ec8a9df86f3dcaaaf912715db35e4852d1da
author Will Deacon <will.deacon@arm.com> Wed Jun 04 16:11:45 2014 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> Wed Jun 04 16:54:17 2014 -0700
tree 1843d72b20376e3ea2c8c44bd1ab242c4a386b19
parent 6e099f557d9c6797c3ee3ee7b5c8cebe543ec1cc

printk: report dropping of messages from logbuf

If the log ring buffer becomes full, we silently overwrite old messages
with new data.  console_unlock will detect this case and fast-forward the
console_* pointers to skip over the corrupted data, but nothing will be
reported to the user.

This patch hijacks the first valid log message after detecting that we
dropped messages and prefixes it with a note detailing how many messages
were dropped.  For long (~1000 char) messages, this will result in some
truncation of the real message, but given that we're dropping things
anyway, that doesn't seem to be the end of the world.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>