From: Josef Bacik <jba...@fb.com>
Things got moved around between the original bpf_override_return patches
and the final version, and now the ftrace kprobe dispatcher assumes if
you modified the ip that you also enabled preemption. Make a comment of
this and enable preemption, this fixes the lockdep splat that happened
when using this feature.
Signed-off-by: Josef Bacik <jba...@fb.com>
---
kernel/trace/trace_kprobe.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index 5db849809a56..91f4b57dab82 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -1322,8 +1322,15 @@ static int kprobe_dispatcher(struct kprobe *kp, struct
pt_regs *regs)
if (tk->tp.flags & TP_FLAG_TRACE)
kprobe_trace_func(tk, regs);
#ifdef CONFIG_PERF_EVENTS
- if (tk->tp.flags & TP_FLAG_PROFILE)
+ if (tk->tp.flags & TP_FLAG_PROFILE) {
ret = kprobe_perf_func(tk, regs);
+ /*
+ * The ftrace kprobe handler leaves it up to us to re-enable
+ * preemption here before returning if we've modified the ip.
+ */
+ if (ret)
+ preempt_enable_no_resched();
+ }
#endif
return ret;
}
--
2.7.5
