#!/usr/bin/python3

from bcc import BPF

prog = '''

#include <uapi/linux/ptrace.h>

BPF_HASH(last);

int do_trace(struct pt_regs *ctx){

u64 ts, *tsp, delta, key = 0;

tsp = last.lookup(&key);

if(tsp != NULL){

delta = bpf_ktime_get_ns() - *tsp;

if (delta < 1000000000){

bpf_trace_printk("%d\\n", delta/ 1000000);

}

last.delete(&key);

}

ts = bpf_ktime_get_ns();

last.update(&key, &ts);

return 0;

}

'''

b = BPF(text=prog)

b.attach_kprobe(event=b.get_syscall_fnname("sync"), fn_name="do_trace")

start = 0

while(1):

try:

(task, pid, cpu, flags, ts, msg) = b.trace_fields()

except ValueError:

continue

if start == 0:

start = ts

ts = ts -start

print("At time %2.f s: multiple syncs detected, last %s ms ago" % (ts, msg))