jump label: Fix deadlock b/w jump_label_mutex vs. text_mutex

register_kprobe() downs the 'text_mutex' and then calls
jump_label_text_reserved(), which downs the 'jump_label_mutex'.
However, the jump label code takes those mutexes in the reverse
order.

Fix by requiring the caller of jump_label_text_reserved() to do
the jump label locking via the newly added: jump_label_lock(),
jump_label_unlock(). Currently, kprobes is the only user
of jump_label_text_reserved().

Reported-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
LKML-Reference: <759032c48d5e30c27f0bba003d09bffa8e9f28bb.1285965957.git.jbaron@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index b67cb180e6e9..1947a1212678 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -18,6 +18,8 @@ struct module;
 extern struct jump_entry __start___jump_table[];
 extern struct jump_entry __stop___jump_table[];
 
+extern void jump_label_lock(void);
+extern void jump_label_unlock(void);
 extern void arch_jump_label_transform(struct jump_entry *entry,
                                  enum jump_label_type type);
 extern void arch_jump_label_text_poke_early(jump_label_t addr);
@@ -59,6 +61,9 @@ static inline int jump_label_text_reserved(void *start, void *end)
         return 0;
 }
 
+static inline void jump_label_lock(void) {}
+static inline void jump_label_unlock(void) {}
+
 #endif
 
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