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 15fafaed027cb24c4e6bc2132498497c3847c6a4..07764c761073d2302f4e412e5aebdaca7f97b046 100644 (file)
--- 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;
 }