From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 24 Feb 2020 14:01:35 +0000 (+0100)
Subject: bpf/tracing: Remove redundant preempt_disable() in __bpf_trace_run()
X-Git-Tag: v5.7-rc1~146^2~287^2~10^2~19
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=f03efe49bd16c017107ff5079d08ea428e390dde;p=thirdparty%2Fkernel%2Flinux.git

bpf/tracing: Remove redundant preempt_disable() in __bpf_trace_run()

__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 <tglx@linutronix.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200224145642.847220186@linutronix.de
---

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index b8661bd0d0280..4d42a5d05ec92 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1516,10 +1516,9 @@ void bpf_put_raw_tracepoint(struct bpf_raw_event_map *btp)
 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();
 }