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Subject[PATCH 1/2] tracing: Add sysctl to enable/disable tracing on oops
Currently we always disable tracing on oops, and this patch
adds a sysctl so one can choose to enable it.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
include/linux/kernel.h | 2 ++
kernel/panic.c | 3 ++-
kernel/sysctl.c | 10 ++++++++++
kernel/trace/ring_buffer.c | 2 ++
4 files changed, 16 insertions(+), 1 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index f61039e..5c4528f 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -516,12 +516,14 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
* Most likely, you want to use tracing_on/tracing_off.
*/
#ifdef CONFIG_RING_BUFFER
+extern int trace_on_oops;
void tracing_on(void);
void tracing_off(void);
/* trace_off_permanent stops recording with no way to bring it back */
void tracing_off_permanent(void);
int tracing_is_on(void);
#else
+#define trace_on_oops 0
static inline void tracing_on(void) { }
static inline void tracing_off(void) { }
static inline void tracing_off_permanent(void) { }
diff --git a/kernel/panic.c b/kernel/panic.c
index 512ab73..22ec502 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -301,7 +301,8 @@ int oops_may_print(void)
*/
void oops_enter(void)
{
- tracing_off();
+ if (!trace_on_oops)
+ tracing_off();
/* can't trust the integrity of the kernel anymore: */
debug_locks_off();
do_oops_enter_exit();
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index cdbe8d0..a768c15 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -537,6 +537,16 @@ static struct ctl_table kern_table[] = {
.proc_handler = &stack_trace_sysctl,
},
#endif
+#ifdef CONFIG_RING_BUFFER
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "trace_on_oops",
+ .data = &trace_on_oops,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+#endif
#ifdef CONFIG_TRACING
{
.ctl_name = CTL_UNNUMBERED,
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 454e74e..fc10962 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -155,6 +155,8 @@ static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;

#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)

+int trace_on_oops;
+
/**
* tracing_on - enable all tracing buffers
*
--
1.6.3

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