From: wangyong <wang.yon...@zte.com.cn>
echo c > proc/sysrq-trigger to trigger system panic, there is no debug
information.
I think the reason is using printk_kthread_func, since panic will call
local_irq_disable to disable interrupts, and then call smp_send_stop to
stop other cpus, the printk thread probably is not waken up by irq_work
and can't print messages during panic.
Using printk_flush_buffer to force flush printk_ringbuffer after all
messages are added to printk_ringbuffer by printk.
Because printk_kthread_func may call console_lock and be blocked when
cpus stop, so printk_flush_buffer does't call console_lock.
Signed-off-by: wangyong <wang.yon...@zte.com.cn>
---
include/linux/printk.h | 1 +
kernel/panic.c | 2 +
kernel/printk/printk.c | 99 ++++++++++++++++++++++++++++++++++++++------------
3 files changed, 78 insertions(+), 24 deletions(-)
diff --git a/include/linux/printk.h b/include/linux/printk.h
index bbfe04c..66a5acf 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -193,6 +193,7 @@ void dump_stack_print_info(const char *log_lvl);
void show_regs_print_info(const char *log_lvl);
extern asmlinkage void dump_stack(void) __cold;
struct wait_queue_head *printk_wait_queue(void);
+void printk_flush_buffer(void);
#else
static inline __printf(1, 0)
int vprintk(const char *s, va_list args)
diff --git a/kernel/panic.c b/kernel/panic.c
index 4d893b6..c19b84b 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -301,6 +301,7 @@ void panic(const char *fmt, ...)
* We can't use the "normal" timers since we just panicked.
*/
pr_emerg("Rebooting in %d seconds..\n", panic_timeout);
+ printk_flush_buffer();
for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
touch_nmi_watchdog();
@@ -334,6 +335,7 @@ void panic(const char *fmt, ...)
disabled_wait();
#endif
pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
+ printk_flush_buffer();
/* Do not scroll important messages printed above */
suppress_printk = 1;
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 6296d34..96e7f07 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1875,6 +1875,59 @@ static void cont_add(int ctx, int cpu, u32 caller_id,
int facility, int level,
}
}
+/*
+ * Record key parameters used to print printk_ringbuffer
+ */
+static struct prb_info {
+ struct prb_iterator iter;
+ char *ext_text;
+ char *text;
+ char *buf;
+ u64 master_seq;
+} prb_info;
+void printk_flush_buffer(void)
+{
+ int ret;
+ size_t len;
+ size_t ext_len;
+ struct printk_log *msg;
+ struct prb_info *info;
+
+ info = &prb_info;
+ if (!info->ext_text || !info->text || !info->buf)
+ return;
+
+ do {
+ ret = prb_iter_next(&info->iter, info->buf,
+ PRINTK_RECORD_MAX, &info->master_seq);
+ if (ret == -ERESTARTSYS) {
+ continue;
+ } else if (ret < 0) {
+ /* iterator invalid, start over */
+ prb_iter_init(&info->iter, &printk_rb, NULL);
+ continue;
+ } else if (ret == 0) {
+ break;
+ }
+
+ msg = (struct printk_log *)info->buf;
+ format_text(msg, info->master_seq, info->ext_text, &ext_len,
+ info->text, &len, printk_time);
+
+ //console_lock(); since printk thread may hold lock
+ call_console_drivers(info->master_seq, info->ext_text, ext_len,
+ info->text, len, msg->level, msg->facility);
+
+ if (len > 0 || ext_len > 0)
+ printk_delay(msg->level);
+ } while (ret != 0);
+
+ kfree(info->ext_text);
+ kfree(info->text);
+ kfree(info->buf);
+}
+EXPORT_SYMBOL(printk_flush_buffer);
+
/* ring buffer used as memory allocator for temporary sprint buffers */
DECLARE_STATIC_PRINTKRB(sprint_rb,
ilog2(PRINTK_RECORD_MAX + sizeof(struct prb_entry) +
@@ -2681,52 +2734,50 @@ late_initcall(printk_late_init);
#if defined CONFIG_PRINTK
static int printk_kthread_func(void *data)
{
- struct prb_iterator iter;
- struct printk_log *msg;
- size_t ext_len;
- char *ext_text;
- u64 master_seq;
- size_t len;
- char *text;
- char *buf;
+
int ret;
+ size_t len;
+ size_t ext_len;
+ struct printk_log *msg;
+ struct prb_info *info;
- ext_text = kmalloc(CONSOLE_EXT_LOG_MAX, GFP_KERNEL);
- text = kmalloc(PRINTK_SPRINT_MAX, GFP_KERNEL);
- buf = kmalloc(PRINTK_RECORD_MAX, GFP_KERNEL);
- if (!ext_text || !text || !buf)
+ info = &prb_info;
+ info->ext_text = kmalloc(CONSOLE_EXT_LOG_MAX, GFP_KERNEL);
+ info->text = kmalloc(PRINTK_SPRINT_MAX, GFP_KERNEL);
+ info->buf = kmalloc(PRINTK_RECORD_MAX, GFP_KERNEL);
+ if (!info->ext_text || !info->text || !info->buf)
return -1;
- prb_iter_init(&iter, &printk_rb, NULL);
+ prb_iter_init(&info->iter, &printk_rb, NULL);
/* the printk kthread never exits */
for (;;) {
- ret = prb_iter_wait_next(&iter, buf,
- PRINTK_RECORD_MAX, &master_seq);
+ ret = prb_iter_wait_next(&info->iter, info->buf,
+ PRINTK_RECORD_MAX, &info->master_seq);
if (ret == -ERESTARTSYS) {
continue;
} else if (ret < 0) {
/* iterator invalid, start over */
- prb_iter_init(&iter, &printk_rb, NULL);
+ prb_iter_init(&info->iter, &printk_rb, NULL);
continue;
}
- msg = (struct printk_log *)buf;
- format_text(msg, master_seq, ext_text, &ext_len, text,
- &len, printk_time);
+ msg = (struct printk_log *)info->buf;
+ format_text(msg, info->master_seq, info->ext_text, &ext_len,
+ info->text, &len, printk_time);
console_lock();
console_may_schedule = 0;
- call_console_drivers(master_seq, ext_text, ext_len, text, len,
- msg->level, msg->facility);
+ call_console_drivers(info->master_seq, info->ext_text, ext_len,
+ info->text, len, msg->level, msg->facility);
if (len > 0 || ext_len > 0)
printk_delay(msg->level);
console_unlock();
}
- kfree(ext_text);
- kfree(text);
- kfree(buf);
+ kfree(info->ext_text);
+ kfree(info->text);
+ kfree(info->buf);
return 0;
}
--
2.15.2
