[patch V3 06/22] bpf/trace: Remove redundant preempt_disable from trace_call_bpf()

From: Thomas Gleixner
Date: Mon Feb 24 2020 - 10:04:54 EST


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@xxxxxxxxxxxxx>
---
V3: New patch. Replaces the previous one which converted this to migrate_disable()
---
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
@@ -83,7 +83,7 @@ unsigned int trace_call_bpf(struct trace
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

out:
__this_cpu_dec(bpf_prog_active);
- preempt_enable();

return ret;
}