From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 24 Feb 2020 14:01:37 +0000 (+0100)
Subject: bpf/trace: Remove redundant preempt_disable from trace_call_bpf()
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=b0a81b94cc50a112601721fcc2f91fab78d7b9f3;p=linux.git

bpf/trace: Remove redundant preempt_disable from trace_call_bpf()

Similar to __bpf_trace_run 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/20200224145643.059995527@linutronix.de
---

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 15fafaed027cb..07764c761073d 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -83,7 +83,7 @@ unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
 	if (in_nmi()) /* not supported yet */
 		return 1;
 
-	preempt_disable();
+	cant_sleep();
 
 	if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
 		/*
@@ -115,7 +115,6 @@ unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx)
 
  out:
 	__this_cpu_dec(bpf_prog_active);
-	preempt_enable();
 
 	return ret;
 }