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SubjectRe: early_printk accessing __log_buf
On Tue, 31 Jul 2007 03:47:59 -0400
"Mike Frysinger" <vapier.adi@gmail.com> wrote:

> attached
> -mike
>
>
> [linux-log_buf_read.patch application/octet-stream (2.4KB)]

Please sort out the email thing if you plan on sending more kernel patches?

Incremental:


From: Andrew Morton <akpm@linux-foundation.org>

- compile fix

- Race fix: oops_in_progress can change at any time

- coding-style fixlets.

Cc: Greg Ungerer <gerg@snapgear.com>
Cc: Mike Frysinger <vapier.adi@gmail.com>
Cc: Mike Frysinger <vapier@gentoo.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Robin Getz <rgetz@blackfin.uclinux.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/kernel.h | 2 +-
kernel/printk.c | 12 ++++++++----
2 files changed, 9 insertions(+), 5 deletions(-)

diff -puN include/linux/kernel.h~early_printk-accessing-__log_buf-fix include/linux/kernel.h
--- a/include/linux/kernel.h~early_printk-accessing-__log_buf-fix
+++ a/include/linux/kernel.h
@@ -168,7 +168,7 @@ static inline int printk(const char *s,
__attribute__ ((format (printf, 1, 2)));
static inline int __cold printk(const char *s, ...) { return 0; }
static inline int log_buf_get_len(void) { return 0; }
-static inline int log_buf_read(int idx); { return 0; }
+static inline int log_buf_read(int idx) { return 0; }
static inline int log_buf_copy(char *dest, int idx, int len) { return 0; }
#endif

diff -puN kernel/printk.c~early_printk-accessing-__log_buf-fix kernel/printk.c
--- a/kernel/printk.c~early_printk-accessing-__log_buf-fix
+++ a/kernel/printk.c
@@ -233,14 +233,17 @@ int log_buf_get_len(void)
int log_buf_copy(char *dest, int idx, int len)
{
int ret, max;
+ bool took_lock = false;

- if (!oops_in_progress)
+ if (!oops_in_progress) {
spin_lock_irq(&logbuf_lock);
+ took_lock = true;
+ }

max = log_buf_get_len();
- if (idx < 0 || idx >= max)
+ if (idx < 0 || idx >= max) {
ret = -1;
- else {
+ } else {
if (len > max)
len = max;
ret = len;
@@ -250,7 +253,7 @@ int log_buf_copy(char *dest, int idx, in
}
}

- if (!oops_in_progress)
+ if (took_lock)
spin_unlock_irq(&logbuf_lock);

return ret;
@@ -262,6 +265,7 @@ int log_buf_copy(char *dest, int idx, in
int log_buf_read(int idx)
{
char ret;
+
if (log_buf_copy(&ret, idx, 1) == 1)
return ret;
else
_
-
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