busybox 初始化进程的 PID 错误答案

【问题标题】：Wrong PID for busybox init processbusybox 初始化进程的 PID 错误
【发布时间】：2014-07-16 22:18:02
【问题描述】：

我已经建立了一个使用busybox的小型嵌入式Linux。我面临一个问题，我不确定它是由busybox还是内核引起的。

问题是，init 进程没有进程 ID 1。这是ps 的输出：

1 root       0:26 [swapper/0]
2 root       0:00 [kthreadd]
3 root       0:00 [ksoftirqd/0]
4 root       0:00 [kworker/0:0]
5 root       0:00 [kworker/0:0H]
6 root       0:00 [kworker/u4:0]
7 root       0:00 [rcu_preempt]
8 root       0:00 [rcu_sched]
...
549 root       0:00 {linuxrc} init
...

我猜init之前的其他进程都是内核进程。这是一个问题的原因是孤立进程的父进程 ID 为 1，它应该是 init 进程，但现在这个 swapper 进程正在接收它们。

当我观察到很多僵尸进程时，我注意到出了点问题。

因此，必须以某种方式将 init 强制设置为 PID 1，或者必须将孤立进程分配给正确的 init PID。

有人知道怎么做吗？

非常感谢！

更新：关于我的设置的更多信息

目标是带有 Xilinx Zynq 芯片的 ARM 板。我使用的是 Xilinx linux Kernel，并自己编译了busybox（v1.20.2）。

命令行是：

ramdisk_size=65536 console=ttyPS0,115200 earlyprintk

以下是启动 init 脚本之前的引导日志：

Uncompressing Linux... done, booting the kernel.
[    0.000000] Booting Linux on physical CPU 0x0
[    0.000000] Linux version 3.13.0-xilinx (cone@cone-ubuntu) (gcc version 4.8.1 (Sourcery CodeBench Lite 2013.11-53) ) #5 SMP PREEMPT Sun J4
[    0.000000] CPU: ARMv7 Processor [413fc090] revision 0 (ARMv7), cr=18c5387d
[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
[    0.000000] Machine model: Xilinx Zynq
[    0.000000] bootconsole [earlycon0] enabled
[    0.000000] Memory policy: Data cache writealloc
[    0.000000] PERCPU: Embedded 8 pages/cpu @c101e000 s10176 r8192 d14400 u32768
[    0.000000] Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 130048
[    0.000000] Kernel command line: ramdisk_size=65536 console=ttyPS0,115200 earlyprintk
[    0.000000] PID hash table entries: 2048 (order: 1, 8192 bytes)
[    0.000000] Dentry cache hash table entries: 65536 (order: 6, 262144 bytes)
[    0.000000] Inode-cache hash table entries: 32768 (order: 5, 131072 bytes)
[    0.000000] Memory: 501272K/524288K available (4781K kernel code, 307K rwdata, 1692K rodata, 197K init, 5345K bss, 23016K reserved, 0K hi)
[    0.000000] Virtual kernel memory layout:
[    0.000000]     vector  : 0xffff0000 - 0xffff1000   (   4 kB)
[    0.000000]     fixmap  : 0xfff00000 - 0xfffe0000   ( 896 kB)
[    0.000000]     vmalloc : 0xe0800000 - 0xff000000   ( 488 MB)
[    0.000000]     lowmem  : 0xc0000000 - 0xe0000000   ( 512 MB)
[    0.000000]     pkmap   : 0xbfe00000 - 0xc0000000   (   2 MB)
[    0.000000]     modules : 0xbf000000 - 0xbfe00000   (  14 MB)
[    0.000000]       .text : 0xc0008000 - 0xc065a600   (6474 kB)
[    0.000000]       .init : 0xc065b000 - 0xc068c7c0   ( 198 kB)
[    0.000000]       .data : 0xc068e000 - 0xc06dac78   ( 308 kB)
[    0.000000]        .bss : 0xc06dac84 - 0xc0c13230   (5346 kB)
[    0.000000] Preemptible hierarchical RCU implementation.
[    0.000000]  RCU lockdep checking is enabled.
[    0.000000]  Dump stacks of tasks blocking RCU-preempt GP.
[    0.000000]  RCU restricting CPUs from NR_CPUS=4 to nr_cpu_ids=2.
[    0.000000] NR_IRQS:16 nr_irqs:16 16
[    0.000000] ps7-slcr mapped to e0802000
[    0.000000] zynq_clock_init: clkc starts at e0802100
[    0.000000] Zynq clock init
[    0.000000] sched_clock: 32 bits at 325MHz, resolution 3ns, wraps every 13215283196ns
[    0.000000] ps7-ttc #0 at e0804000, irq=43
[    0.000000] Console: colour dummy device 80x30
[    0.000000] Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar
[    0.000000] ... MAX_LOCKDEP_SUBCLASSES:  8
[    0.000000] ... MAX_LOCK_DEPTH:          48
[    0.000000] ... MAX_LOCKDEP_KEYS:        8191
[    0.000000] ... CLASSHASH_SIZE:          4096
[    0.000000] ... MAX_LOCKDEP_ENTRIES:     16384
[    0.000000] ... MAX_LOCKDEP_CHAINS:      32768
[    0.000000] ... CHAINHASH_SIZE:          16384
[    0.000000]  memory used by lock dependency info: 3695 kB
[    0.000000]  per task-struct memory footprint: 1152 bytes
[   13.207599] Calibrating delay loop... 1292.69 BogoMIPS (lpj=6463488)
[   13.207606] pid_max: default: 32768 minimum: 301
[   13.207607] Mount-cache hash table entries: 512
[   13.207609] CPU: Testing write buffer coherency: ok
[   13.207610] CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
[   13.207611] Setting up static identity map for 0x489b98 - 0x489bf0
[   13.207612] L310 cache controller enabled
[   13.207613] l2x0: 8 ways, CACHE_ID 0x410000c8, AUX_CTRL 0x72760000, Cache size: 512 kB
[   13.207627] CPU1: Booted secondary processor
[   13.207641] CPU1: thread -1, cpu 1, socket 0, mpidr 80000001
[   13.207642] Brought up 2 CPUs
[   13.207644] SMP: Total of 2 processors activated.
[   13.207644] CPU: All CPU(s) started in SVC mode.
[   13.207646] devtmpfs: initialized
[   13.207647] VFP support v0.3: implementor 41 architecture 3 part 30 variant 9 rev 4
[   13.207650] regulator-dummy: no parameters
[   13.207651] NET: Registered protocol family 16
[   13.207651] DMA: preallocated 256 KiB pool for atomic coherent allocations
[   13.207654] cpuidle: using governor ladder
[   13.207654] cpuidle: using governor menu
[   13.207658] syscon f8000000.ps7-slcr: regmap [mem 0xf8000000-0xf8000fff] registered
[   13.207660] hw-breakpoint: found 5 (+1 reserved) breakpoint and 1 watchpoint registers.
[   13.207662] hw-breakpoint: maximum watchpoint size is 4 bytes.
[   13.207663] zynq-ocm f800c000.ps7-ocmc: ZYNQ OCM pool: 256 KiB @ 0xe0880000
[   13.207672] bio: create slab <bio-0> at 0
[   13.207674] vgaarb: loaded
[   13.207674] SCSI subsystem initialized
[   13.207675] usbcore: registered new interface driver usbfs
[   13.207676] usbcore: registered new interface driver hub
[   13.207677] usbcore: registered new device driver usb
[   13.207678] media: Linux media interface: v0.10
[   13.207679] Linux video capture interface: v2.00
[   13.207680] pps_core: LinuxPPS API ver. 1 registered
[   13.207681] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <giometti@linux.it>
[   13.207682] PTP clock support registered
[   13.207683] EDAC MC: Ver: 3.0.0
[   13.207685] DMA-API: preallocated 4096 debug entries
[   13.207686] DMA-API: debugging enabled by kernel config
[   13.207687] Switched to clocksource arm_global_timer
[   13.207696] NET: Registered protocol family 2
[   13.207697] TCP established hash table entries: 4096 (order: 2, 16384 bytes)
[   13.207698] TCP bind hash table entries: 4096 (order: 5, 147456 bytes)
[   13.207699] TCP: Hash tables configured (established 4096 bind 4096)
[   13.207700] TCP: reno registered
[   13.207701] UDP hash table entries: 256 (order: 2, 20480 bytes)
[   13.207702] UDP-Lite hash table entries: 256 (order: 2, 20480 bytes)
[   13.207703] NET: Registered protocol family 1
[   13.207704] RPC: Registered named UNIX socket transport module.
[   13.207705] RPC: Registered udp transport module.
[   13.207706] RPC: Registered tcp transport module.
[   13.207707] RPC: Registered tcp NFSv4.1 backchannel transport module.
[   13.207708] Trying to unpack rootfs image as initramfs...
[   13.207709] rootfs image is not initramfs (no cpio magic); looks like an initrd
[   13.207717] Freeing initrd memory: 6004K (df551000 - dfb2e000)
[   13.207718] hw perfevents: enabled with ARMv7 Cortex-A9 PMU driver, 7 counters available
[   13.207722] jffs2: version 2.2. (NAND) (SUMMARY)  © 2001-2006 Red Hat, Inc.
[   13.207723] msgmni has been set to 990
[   13.207724] io scheduler noop registered
[   13.207724] io scheduler deadline registered
[   13.207725] io scheduler cfq registered (default)
[   13.207728] dma-pl330 f8003000.ps7-dma: unable to set the seg size
[   13.207729] dma-pl330 f8003000.ps7-dma: Loaded driver for PL330 DMAC-2364208
[   13.207731] dma-pl330 f8003000.ps7-dma:      DBUFF-128x8bytes Num_Chans-8 Num_Peri-4 Num_Events-16
[   13.207733] e0001000.serial: ttyPS0 at MMIO 0xe0001000 (irq = 82, base_baud = 3125000) is a xuartps
[   13.207734] console [ttyPS0] enabled
[   13.207734] console [ttyPS0] enabled
[   13.207735] bootconsole [earlycon0] disabled
[   13.207735] bootconsole [earlycon0] disabled
[   13.207737] xdevcfg f8007000.ps7-dev-cfg: ioremap 0xf8007000 to e0866000
[   13.207743] brd: module loaded
[   13.207746] loop: module loaded
[   13.207748] zynq-qspi e000d000.ps7-qspi: master is unqueued, this is deprecated
[   13.207749] zynq-qspi e000d000.ps7-qspi: at 0xE000D000 mapped to 0xE0868000, irq=51
[   13.207752] e1000e: Intel(R) PRO/1000 Network Driver - 2.3.2-k
[   13.207753] e1000e: Copyright(c) 1999 - 2013 Intel Corporation.
[   13.207754] libphy: XEMACPS mii bus: probed
[   13.207755] xemacps e000b000.ps7-ethernet: pdev->id -1, baseaddr 0xe000b000, irq 54
[   13.207757] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
[   13.207758] ehci-pci: EHCI PCI platform driver
[   13.207759] ULPI transceiver vendor/product ID 0x0424/0x0007
[   13.207760] Found SMSC USB3320 ULPI transceiver.
[   13.207761] ULPI integrity check: passed.
[   13.207761] zynq-ehci zynq-ehci.0: Xilinx Zynq USB EHCI Host Controller
[   13.207763] zynq-ehci zynq-ehci.0: new USB bus registered, assigned bus number 1
[   13.207769] zynq-ehci zynq-ehci.0: irq 53, io mem 0x00000000
[   13.207772] zynq-ehci zynq-ehci.0: USB 2.0 started, EHCI 1.00
[   13.207773] usb usb1: New USB device found, idVendor=1d6b, idProduct=0002
[   13.207774] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[   13.207775] usb usb1: Product: Xilinx Zynq USB EHCI Host Controller
[   13.207776] usb usb1: Manufacturer: Linux 3.13.0-xilinx ehci_hcd
[   13.207777] usb usb1: SerialNumber: zynq-ehci.0
[   13.207779] hub 1-0:1.0: USB hub found
[   13.207779] hub 1-0:1.0: 1 port detected
[   13.207781] usbcore: registered new interface driver usb-storage
[   13.207782] mousedev: PS/2 mouse device common for all mice
[   13.207783] i2c /dev entries driver
[   13.207784] cdns-i2c e0004000.ps7-i2c: 400 kHz mmio e0004000 irq 57
[   13.207787] xadcps f8007100.ps7-xadc: enabled:       yes     reference:      external
[   13.207788] cdns-wdt f8005000.ps7-wdt: Xilinx Watchdog Timer at e0876000 with timeout 10s
[   13.207790] zynq-edac f8006000.ps7-ddrc: ecc not enabled
[   13.207791] Xilinx Zynq CpuIdle Driver started
[   13.207590] sdhci: Secure Digital Host Controller Interface driver
[   13.207591] sdhci: Copyright(c) Pierre Ossman
[   13.207592] sdhci-pltfm: SDHCI platform and OF driver helper
[   13.207593] sdhci-arasan e0100000.ps7-sdio: dummy supplies not allowed
[   13.207594] mmc0: no vqmmc regulator found
[   13.207595] sdhci-arasan e0100000.ps7-sdio: dummy supplies not allowed
[   13.207596] mmc0: no vmmc regulator found
[   13.207603] mmc0: SDHCI controller on e0100000.ps7-sdio [e0100000.ps7-sdio] using ADMA
[   13.207608] usbcore: registered new interface driver usbhid
[   13.207608] usbhid: USB HID core driver
[   13.207609] TCP: cubic registered
[   13.207610] NET: Registered protocol family 17
[   13.207611] Registering SWP/SWPB emulation handler
[   13.207612] drivers/rtc/hctosys.c: unable to open rtc device (rtc0)
[   13.207614] mmc0: new high speed SDHC card at address 59b4
[   13.207615] mmcblk0: mmc0:59b4 USD   14.7 GiB 
[   13.207617]  mmcblk0: p1 p2
[   13.207618] RAMDISK: gzip image found at block 0
[   13.207691] usb 1-1: new high-speed USB device number 2 using zynq-ehci
[   13.207707] VFS: Mounted root (ext2 filesystem) on device 1:0.
Starting rcS...

@sawdust：我没有/init 文件。我认为/linuxrc 是第一个被执行的东西，它只是busybox 的符号链接。

【问题讨论】：

首先要做的是查看目标文件 /init 中的内容。
我认为你需要把更多的信息，比如内核命令行参数，你嵌入式Linux系统的引导日志，以便分析。
“这是启动脚本之前的引导日志” -- 你漏掉了最重要的部分！硬件初始化（您发布的）对此问题不感兴趣。您是如何构建 rootfs 的？

标签： linux embedded-linux busybox

【解决方案1】：

我想我解决了这个问题。显然，将root=/dev/ram 添加到引导参数就可以了。我看到有人在网上某处推荐过，但我再也找不到链接了。我不完全确定为什么这是必要的，但它有效:-)

【讨论】：

如果有人通过 google 偶然发现了这个问题：这样做的原因是您不再使用 initrd，而是使用普通的 init。这里将tmpfs 挂载为rootfs，并从那里运行init。此外，您应该将 init=/linuxrc 参数传递给内核，或者将 init 移动到默认位置（如 /sbin/init）以使其实际工作。