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authorWill Deacon <will.deacon@arm.com>2014-06-05 03:11:45 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-05 03:54:17 +0400
commit84b5ec8a9df86f3dcaaaf912715db35e4852d1da (patch)
tree1843d72b20376e3ea2c8c44bd1ab242c4a386b19 /kernel/printk
parent6e099f557d9c6797c3ee3ee7b5c8cebe543ec1cc (diff)
downloadlinux-84b5ec8a9df86f3dcaaaf912715db35e4852d1da.tar.xz
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>
Diffstat (limited to 'kernel/printk')
-rw-r--r--kernel/printk/printk.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 35d9db251903..923c5d4e4202 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2157,10 +2157,15 @@ again:
}
if (console_seq < log_first_seq) {
+ len = sprintf(text, "** %u printk messages dropped ** ",
+ (unsigned)(log_first_seq - console_seq));
+
/* messages are gone, move to first one */
console_seq = log_first_seq;
console_idx = log_first_idx;
console_prev = 0;
+ } else {
+ len = 0;
}
skip:
if (console_seq == log_next_seq)
@@ -2185,8 +2190,8 @@ skip:
}
level = msg->level;
- len = msg_print_text(msg, console_prev, false,
- text, sizeof(text));
+ len += msg_print_text(msg, console_prev, false,
+ text + len, sizeof(text) - len);
console_idx = log_next(console_idx);
console_seq++;
console_prev = msg->flags;