Steven Rostedt [off-list ref] writes:

On Fri, 14 Feb 2020 14:39:21 +0100
Thomas Gleixner [off-list ref] wrote:

quoted

__bpf_trace_run() disables preemption around the BPF_PROG_RUN() invocation.

This is redundant because __bpf_trace_run() is invoked from a trace point
via __DO_TRACE() which already disables preemption _before_ invoking any of
the functions which are attached to a trace point.

Remove it.

Signed-off-by: Thomas Gleixner <redacted>
---
 kernel/trace/bpf_trace.c |    2 --
 1 file changed, 2 deletions(-)

--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c

@@ -1476,9 +1476,7 @@ static __always_inline
 void __bpf_trace_run(struct bpf_prog *prog, u64 *args)
 {

Should there be a "cant_migrate()" added here?

A cant_sleep() is the right thing to add as this really needs to stay
non-preemptible. Hmm?

quoted

 	rcu_read_lock();
-	preempt_disable();
 	(void) BPF_PROG_RUN(prog, args);
-	preempt_enable();
 	rcu_read_unlock();
 }

Thanks,

        tglx