linux-kernel - [patch V2 10/20] trace/bpf: Use migrate disable in trace_call

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Date:   Thu, 20 Feb 2020 21:45:27 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     David Miller <davem@...emloft.net>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Sebastian Sewior <bigeasy@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Clark Williams <williams@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Ingo Molnar <mingo@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [patch V2 10/20] trace/bpf: Use migrate disable in trace_call_bpf()

BPF does not require preemption disable. It only requires to stay on the
same CPU while running a program. Reflect this by replacing
preempt_disable/enable() with migrate_disable/enable() pairs.

On a non-RT kernel this maps to preempt_disable/enable().

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/trace/bpf_trace.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -83,7 +83,7 @@ unsigned int trace_call_bpf(struct trace
 	if (in_nmi()) /* not supported yet */
 		return 1;
 
-	preempt_disable();
+	migrate_disable();
 
 	if (unlikely(__this_cpu_inc_return(bpf_prog_active) != 1)) {
 		/*
@@ -115,7 +115,7 @@ unsigned int trace_call_bpf(struct trace
 
  out:
 	__this_cpu_dec(bpf_prog_active);
-	preempt_enable();
+	migrate_enable();
 
 	return ret;
 }