Subject: [patch V3 04/22] bpf/tracing: Remove redundant preempt_disable() in __bpf_trace_run()

From: Thomas Gleixner <[email-masked]>
Date: Mon, 24 Feb 2020 15:01:35 +0100

__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 and add a cant_sleep() check.

Signed-off-by: Thomas Gleixner <[email-masked]>
---
V3: Add a cant_sleep() check. 
---
 kernel/trace/bpf_trace.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1516,10 +1516,9 @@ void bpf_put_raw_tracepoint(struct bpf_r
 static __always_inline
 void __bpf_trace_run(struct bpf_prog *prog, u64 *args)
 {
+	cant_sleep();
 	rcu_read_lock();
-	preempt_disable();
 	(void) BPF_PROG_RUN(prog, args);
-	preempt_enable();
 	rcu_read_unlock();
 }