Re: [PATCH bpf-next] selftests/bpf: Switch test_vmlinux to use hrtimer_range_start_ns.

2020-06-30 Thread Yonghong Song
On 6/30/20 5:10 PM, Hao Luo wrote: Ok, with the help of my colleague Ian Rogers, I think we solved the mystery. Clang actually inlined hrtimer_nanosleep() inside SyS_nanosleep(), so there is no call to that function throughout the path of the nanosleep syscall. I've been looking at the functio

Re: [PATCH bpf-next] selftests/bpf: Switch test_vmlinux to use hrtimer_range_start_ns.

2020-06-30 Thread Andrii Nakryiko
On Tue, Jun 30, 2020 at 1:47 PM Hao Luo wrote: > > The test_vmlinux test uses hrtimer_nanosleep as hook to test tracing > programs. But it seems Clang may have done an aggressive optimization, > causing fentry and kprobe to not hook on this function properly on a > Clang build kernel. > > A possib

Re: [PATCH bpf-next] selftests/bpf: Switch test_vmlinux to use hrtimer_range_start_ns.

2020-06-30 Thread Yonghong Song
On 6/30/20 11:49 AM, Hao Luo wrote: The test_vmlinux test uses hrtimer_nanosleep as hook to test tracing programs. But it seems Clang may have done an aggressive optimization, causing fentry and kprobe to not hook on this function properly on a Clang build kernel. Could you explain why it do