xtask: wait for the stdin echo instead of a fixed delay

[stlankes]

test_stdin fed each message to the guest with a one-second pause and then terminated QEMU immediately, reading the echoed output only afterwards. On a slow target the last echo had not been written yet when QEMU was killed, so the collected output ended mid-line and the assertion failed intermittently. This showed up on aarch64_be, which is emulated without hardware acceleration.

Collect the guest's stdout on a background thread and wait until every message has been echoed (bounded by a 60 s timeout) before terminating QEMU. The check no longer depends on the guest keeping pace with a fixed schedule.

[github-actions]

Benchmark Results

Details

Benchmark	Current: 2e47df2	Previous: 2e23902	Performance Ratio
startup_benchmark Build Time	84.02 s	80.34 s	1.05 ❗
startup_benchmark File Size	0.80 MB	0.80 MB	1
Startup Time - 1 core	0.74 s (±0.02 s)	0.75 s (±0.02 s)	1.00
Startup Time - 2 cores	0.74 s (±0.02 s)	0.74 s (±0.02 s)	1.00
Startup Time - 4 cores	0.76 s (±0.02 s)	0.74 s (±0.02 s)	1.02
multithreaded_benchmark Build Time	82.74 s	82.11 s	1.01 ❗
multithreaded_benchmark File Size	0.86 MB	0.86 MB	1.00 ❗
Multithreaded Pi Efficiency - 2 Threads	86.11 % (±6.21 %)	85.89 % (±6.61 %)	1.00
Multithreaded Pi Efficiency - 4 Threads	43.27 % (±2.85 %)	43.43 % (±2.56 %)	1.00
Multithreaded Pi Efficiency - 8 Threads	25.23 % (±1.64 %)	25.76 % (±1.53 %)	0.98
micro_benchmarks Build Time	83.01 s	80.40 s	1.03 ❗
micro_benchmarks File Size	0.86 MB	0.86 MB	1
Scheduling time - 1 thread	63.08 ticks (±2.71 ticks)	62.65 ticks (±4.06 ticks)	1.01
Scheduling time - 2 threads	35.13 ticks (±4.67 ticks)	34.08 ticks (±4.10 ticks)	1.03
Micro - Time for syscall (getpid)	3.23 ticks (±0.44 ticks)	3.45 ticks (±0.58 ticks)	0.94
Memcpy speed - (built_in) block size 4096	79862.47 MByte/s (±55309.85 MByte/s)	82448.38 MByte/s (±56997.13 MByte/s)	0.97
Memcpy speed - (built_in) block size 1048576	30514.62 MByte/s (±24654.34 MByte/s)	30585.98 MByte/s (±24707.84 MByte/s)	1.00
Memcpy speed - (built_in) block size 16777216	25841.48 MByte/s (±21394.19 MByte/s)	26340.06 MByte/s (±21720.96 MByte/s)	0.98
Memset speed - (built_in) block size 4096	79708.52 MByte/s (±55200.43 MByte/s)	82292.76 MByte/s (±56891.50 MByte/s)	0.97
Memset speed - (built_in) block size 1048576	31261.86 MByte/s (±25087.35 MByte/s)	31323.85 MByte/s (±25145.86 MByte/s)	1.00
Memset speed - (built_in) block size 16777216	26562.34 MByte/s (±21845.04 MByte/s)	27104.68 MByte/s (±22209.94 MByte/s)	0.98
Memcpy speed - (rust) block size 4096	73365.46 MByte/s (±51321.77 MByte/s)	74097.96 MByte/s (±51811.44 MByte/s)	0.99
Memcpy speed - (rust) block size 1048576	30354.41 MByte/s (±24671.83 MByte/s)	30361.60 MByte/s (±24602.37 MByte/s)	1.00
Memcpy speed - (rust) block size 16777216	26213.43 MByte/s (±21555.49 MByte/s)	27625.34 MByte/s (±22806.88 MByte/s)	0.95
Memset speed - (rust) block size 4096	73816.26 MByte/s (±51650.77 MByte/s)	74373.47 MByte/s (±51976.48 MByte/s)	0.99
Memset speed - (rust) block size 1048576	31094.07 MByte/s (±25098.93 MByte/s)	31110.89 MByte/s (±25033.24 MByte/s)	1.00
Memset speed - (rust) block size 16777216	26967.38 MByte/s (±22038.46 MByte/s)	28386.93 MByte/s (±23265.03 MByte/s)	0.95
alloc_benchmarks Build Time	80.58 s	74.76 s	1.08 ❗
alloc_benchmarks File Size	0.87 MB	0.87 MB	1.00 ❗
Allocations - Allocation success	91.31 %	91.31 %	1
Allocations - Deallocation success	100.00 %	100.00 %	1
Allocations - Pre-fail Allocations	61.44 %	61.44 %	1
Allocations - Average Allocation time	7842.45 Ticks (±462.89 Ticks)	5860.58 Ticks (±98.43 Ticks)	1.34 ❗
Allocations - Average Allocation time (no fail)	8351.30 Ticks (±393.67 Ticks)	6554.81 Ticks (±92.86 Ticks)	1.27 ❗
Allocations - Average Deallocation time	1428.52 Ticks (±333.49 Ticks)	1805.01 Ticks (±250.35 Ticks)	0.79
mutex_benchmark Build Time	78.05 s	79.82 s	0.98 ❗
mutex_benchmark File Size	0.86 MB	0.86 MB	1.00 ❗
Mutex Stress Test Average Time per Iteration - 1 Threads	12.14 ns (±0.45 ns)	12.10 ns (±0.41 ns)	1.00
Mutex Stress Test Average Time per Iteration - 2 Threads	41.58 ns (±2.64 ns)	40.26 ns (±1.68 ns)	1.03

This comment was automatically generated by workflow using github-action-benchmark.

[mkroening]

This alone does not seem to fix the issue: https://github.com/hermit-os/kernel/actions/runs/29735468922/job/88329640752?pr=2293

[stlankes]

If remember correctly, this issue was fixed by 2f10654