核心：“迴聲 0 > /proc/sys/kernel/hung_task_timeout_secs”

我在系統日誌中遇到了這個錯誤。知道這是什麼意思嗎？系統在Ubuntu 12.04上執行，核心：3.8.0-35-generic #52~precise1

在我看來，嘗試寫入磁碟時失敗了……

[151850.317166] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[151850.318428]  ffff8803640f5be8 0000000000000082 0000000034c733da ffff88040e233ec0
[151850.318444]  ffff880408149740 ffff880403c6c5c0 0000000000000001 ffff8803edae80a8
[151850.318468]  [<ffffffff816f41c9>] schedule+0x29/0x70
[151850.318481]  [<ffffffff816f30b7>] __mutex_lock_slowpath+0xd7/0x150
[151850.318497]  [<ffffffff816f2cca>] mutex_lock+0x2a/0x50
[151850.318510]  [<ffffffff811aa006>] path_lookupat+0x236/0x7a0
[151850.318523]  [<ffffffff811aade0>] ? getname_flags.part.31+0x30/0x150
[151850.318537]  [<ffffffff811aaf6e>] ? getname_flags+0x6e/0x80
[151850.318552]  [<ffffffff813141f4>] ? apparmor_inode_getattr+0x54/0x60
[151850.318565]  [<ffffffff811bb929>] ? mntput_no_expire+0x49/0x160
[151850.318578]  [<ffffffff811ab711>] user_path_at+0x11/0x20
[151850.318588]  [<ffffffff811a0c3e>] vfs_lstat+0x1e/0x20
[151850.318602]  [<ffffffff816fdf5d>] system_call_fastpath+0x1a/0x1f
[151850.319634] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[151850.376552]  [<ffffffff816f41c9>] schedule+0x29/0x70
[151850.376565]  [<ffffffff816f30b7>] __mutex_lock_slowpath+0xd7/0x150
[151850.376579]  [<ffffffff816f2cca>] mutex_lock+0x2a/0x50
[151850.376590]  [<ffffffff811aa006>] path_lookupat+0x236/0x7a0
[151850.376602]  [<ffffffff811aade0>] ? getname_flags.part.31+0x30/0x150
[151850.376616]  [<ffffffff811aaf6e>] ? getname_flags+0x6e/0x80
[151850.376680]  [<ffffffff813141f4>] ? apparmor_inode_getattr+0x54/0x60
[151850.376691]  [<ffffffff811bb929>] ? mntput_no_expire+0x49/0x160
[151850.376704]  [<ffffffff811ab711>] user_path_at+0x11/0x20
[151850.406554] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[151850.465132] sftp-server     D ffff880403bfdf60     0 15199      1 0x00000000
[151850.465158]  ffff8803d2c87fd8 ffff8803d2c87fd8 ffff8803d2c87fd8 0000000000013ec0
[151850.465173]  ffffffff81c15440 ffff88040583ae80 0000000000000001 ffff8803edae80a8
[151850.465263]  [<ffffffff811aa006>] path_lookupat+0x236/0x7a0
[151850.465269]  [<ffffffff81186441>] ? kmem_cache_alloc+0x31/0x140
[151850.465275]  [<ffffffff811aade0>] ? getname_flags.part.31+0x30/0x150
[151850.465283]  [<ffffffff811aa5a4>] filename_lookup+0x34/0xc0
[151850.465289]  [<ffffffff811aaf6e>] ? getname_flags+0x6e/0x80
[151850.465296]  [<ffffffff811ab6b9>] user_path_at_empty+0x59/0xa0
[151850.465303]  [<ffffffff813141f4>] ? apparmor_inode_getattr+0x54/0x60
[151850.465309]  [<ffffffff81087e9a>] ? lg_local_unlock+0x1a/0x20
[151850.465315]  [<ffffffff811bb929>] ? mntput_no_expire+0x49/0x160
[151850.465320]  [<ffffffff811a0946>] ? cp_new_stat+0x116/0x130
[151850.465327]  [<ffffffff811ab711>] user_path_at+0x11/0x20
[151850.465332]  [<ffffffff811a0bc1>] vfs_fstatat+0x51/0xb0
[151850.465337]  [<ffffffff811a0c3e>] vfs_lstat+0x1e/0x20
[151850.465343]  [<ffffffff811a0dea>] sys_newlstat+0x1a/0x40
[151850.465350]  [<ffffffff816fdf5d>] system_call_fastpath+0x1a/0x1f

如果某個程序（在這種情況下sftp-server）在 120 秒（預設限制）內沒有獲得 CPU，則會出現該消息。這可能是由系統上的高負載引起的。通常這可能是由於等待任何資源，最有可能的候選者是 CPU、磁碟和網路。

在調試此類問題時，您可以測試磁碟上的寫入速度：

$ dd if=/dev/zero of=/tmp/output conv=fdatasync bs=384k count=1k; rm -f /tmp/output
1024+0 records in
1024+0 records out
402653184 bytes (403 MB) copied, 2753.13 s, 146 kB/s

您應該期望以 MB/s 為單位的值，例如50-230 MB/s取決於硬碟驅動器。在這種情況下，吞吐量146 kB/s極低，可能會導致此類核心消息。

您還可以使用它iostat -x 5來監視磁碟使用率。

引用自：https://unix.stackexchange.com/questions/114712