From 5c5d5ca51abd728c8de3be43ffd6bb00f977bfcd Mon Sep 17 00:00:00 2001 From: Kay Sievers Date: Thu, 10 May 2012 04:32:53 +0200 Subject: [PATCH] printk() - do not merge continuation lines of different threads This prevents the merging of printk() continuation lines of different threads, in the case they race against each other. It should properly isolate "atomic" single-line printk() users from continuation users, to make sure the single-line users will never be merged with the racy continuation ones. Cc: Linus Torvalds Cc: Ingo Molnar Cc: Jonathan Corbet Cc: Sasha Levin Signed-off-by: Kay Sievers Signed-off-by: Greg Kroah-Hartman --- kernel/printk.c | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/kernel/printk.c b/kernel/printk.c index 7b432951f91..301fb0f09fb 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -1230,12 +1230,13 @@ asmlinkage int vprintk_emit(int facility, int level, static size_t buflen; static int buflevel; static char textbuf[LOG_LINE_MAX]; + static struct task_struct *cont; char *text = textbuf; size_t textlen; unsigned long flags; int this_cpu; bool newline = false; - bool cont = false; + bool prefix = false; int printed_len = 0; boot_delay_msec(); @@ -1295,20 +1296,16 @@ asmlinkage int vprintk_emit(int facility, int level, case '0' ... '7': if (level == -1) level = text[1] - '0'; - text += 3; - textlen -= 3; - break; - case 'c': /* KERN_CONT */ - cont = true; case 'd': /* KERN_DEFAULT */ + prefix = true; + case 'c': /* KERN_CONT */ text += 3; textlen -= 3; - break; } } - if (buflen && (!cont || dict)) { - /* no continuation; flush existing buffer */ + if (buflen && (prefix || dict || cont != current)) { + /* flush existing buffer */ log_store(facility, buflevel, NULL, 0, buf, buflen); printed_len += buflen; buflen = 0; @@ -1342,6 +1339,10 @@ asmlinkage int vprintk_emit(int facility, int level, dict, dictlen, text, textlen); printed_len += textlen; } + cont = NULL; + } else { + /* remember thread which filled the buffer */ + cont = current; } /* -- 2.34.1