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printk() - do not merge continuation lines of different threads

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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 <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Kay Sievers <kay@vrfy.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Kay Sievers 2012-05-10 04:32:53 +02:00 committed by Greg Kroah-Hartman
parent 7f3a781d6f
commit 5c5d5ca51a
1 changed files with 10 additions and 9 deletions
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19
kernel/printk.c
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@ -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;
}
/*