printk: Implement some unlocked kmsg_dump functions

If used from KDB, the locked variants are prone to deadlocks (suppose we
got to the debugger w/ the logbuf lock held).

So, we have to implement a few routines that grab no logbuf lock.

Yet we don't need these functions in modules, so we don't export them.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
index d6bd50110ec2..2e7a1e032c71 100644
--- a/include/linux/kmsg_dump.h
+++ b/include/linux/kmsg_dump.h
@@ -55,12 +55,17 @@ struct kmsg_dumper {
 #ifdef CONFIG_PRINTK
 void kmsg_dump(enum kmsg_dump_reason reason);
 
+bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper, bool syslog,
+                               char *line, size_t size, size_t *len);
+
 bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
                         char *line, size_t size, size_t *len);
 
 bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
                           char *buf, size_t size, size_t *len);
 
+void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper);
+
 void kmsg_dump_rewind(struct kmsg_dumper *dumper);
 
 int kmsg_dump_register(struct kmsg_dumper *dumper);
@@ -71,6 +76,13 @@ static inline void kmsg_dump(enum kmsg_dump_reason reason)
 {
 }
 
+static inline bool kmsg_dump_get_line_nolock(struct kmsg_dumper *dumper,
+                                             bool syslog, const char *line,
+                                             size_t size, size_t *len)
+{
+        return false;
+}
+
 static inline bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog,
                                 const char *line, size_t size, size_t *len)
 {
@@ -83,6 +95,10 @@ static inline bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog,
         return false;
 }
 
+static inline void kmsg_dump_rewind_nolock(struct kmsg_dumper *dumper)
+{
+}
+
 static inline void kmsg_dump_rewind(struct kmsg_dumper *dumper)
 {
 }