Race condition during TLE results in "unknown syscall disallowed"

[Xyene]

Start grading aplusb/1 in PY2...
Test case 1 AC [0.046s (0.086s) | 4404kb] 
Test case 2 AC [0.049s (0.092s) | 4404kb] 
WARNING 2018-12-13 17:57:53,428 sandbox Shocker activated and killed 987
ptrace(PTRACE_PEEKUSER): No such process
INFO 2018-12-13 17:57:53,430 error Protection fault on: 18446744073709551615 (unknown)
INFO 2018-12-13 17:57:53,431 error Arg0: 0x0000000000000000
INFO 2018-12-13 17:57:53,431 error Arg1: 0x0000000000005401
INFO 2018-12-13 17:57:53,431 error Arg2: 0x00007ffffffedff0
INFO 2018-12-13 17:57:53,431 error Arg3: 0x00007fffff447fc0
INFO 2018-12-13 17:57:53,431 error Arg4: 0x00007ffffffee030
INFO 2018-12-13 17:57:53,431 error Arg5: 0x00000000008f9920
Test case 3 TLE [2.468s (5.058s) | 4352kb] (unknown syscall disallowed) {RTE, WA}
Done grading aplusb/1.

ptrace fails, so the result remains garbage data which is then interpreted as an invalid syscall. We should probably just abort if ptrace reports the process no longer exists.

[Xyene]

Since this issue was reported in 2018, this is a note (for myself) that this still happens.

WARNING 2020-08-31 04:18:12,479 10932 tracer Shocker activated and killed 11016
WARNING 2020-08-31 04:18:12,480 10932 tracer Request the killing of process: 11016
ptrace(PTRACE_PEEKUSER): No such process
WARNING 2020-08-31 04:18:12,486 10932 error Protection fault on: 18446744073709551615 (unknown)
WARNING 2020-08-31 04:18:12,486 10932 error Arg0: 0x0000000000000001
WARNING 2020-08-31 04:18:12,486 10932 error Arg1: 0x00000000081d6b70
WARNING 2020-08-31 04:18:12,486 10932 error Arg2: 0x0000000000000006
WARNING 2020-08-31 04:18:12,487 10932 error Arg3: 0x00000000081d6b70
WARNING 2020-08-31 04:18:12,487 10932 error Arg4: 0x0000000000000001
WARNING 2020-08-31 04:18:12,487 10932 error Arg5: 0x0000000000000000
INFO 2020-08-31 04:18:12,487 62 judge Test case 19 TLE [1.720s (2.001s) | 4088kb] (unknown syscall disallowed) {RTE, WA}