标题: swapper process can not be stopped. [打印本页] 作者: edwinrong 时间: 2008-12-23 17:05 标题: swapper process can not be stopped.
[01] swapper process can not be stops.
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Description:
Recently, I do some work related to PM subsystem. My aim is to put system into sleep mode. Some hardware-dependent work has been implemented in “pm.c” and “sleep.S”.
As is known to all, PM subsystem provides interface “pm_suspend()” to achieve this goal, which can be invoked by issuing:
“echo mem > /sys/power/state”
But, after issuing the above command, it comes out something abnormal as follows:
# echo mem > /sys/power/state
Stopping tasks: ===============
stopping tasks timed out after 20 seconds (1 tasks remaining):
swapper
Restarting tasks... Strange, swapper not stopped
Done
The above logs tell that there is one process called “swapper” cannot be stopped.
My question is “What’s this “swapper” process is?”, “Under what condition, the process will be spawned?”
Thanks in advance!
To see what’s the process, execute ps command:
# ps aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 2.4 0.5 1500 560 ? Ss 00:00 0:01 init [3]
root 2 0.0 0.0 0 0 ? S 00:00 0:00 [posix_cpu_tim]
root 3 0.0 0.0 0 0 ? S 00:00 0:00 [softirq-high/]
root 4 0.0 0.0 0 0 ? S 00:00 0:00 [softirq-timer]
root 5 0.0 0.0 0 0 ? S 00:00 0:00 [softirq-net-t]
root 6 0.0 0.0 0 0 ? S 00:00 0:00 [softirq-net-r]
root 7 0.0 0.0 0 0 ? S 00:00 0:00 [softirq-block]
root 8 0.0 0.0 0 0 ? S 00:00 0:00 [softirq-taskl]
root 9 0.0 0.0 0 0 ? S 00:00 0:00 [softirq-rcu/0]
root 10 0.1 0.0 0 0 ? S< 00:00 0:00 [desched/0]
root 11 0.0 0.0 0 0 ? S< 00:00 0:00 [events/0]
root 12 0.1 0.0 0 0 ? S< 00:00 0:00 [khelper]
root 13 0.0 0.0 0 0 ? S< 00:00 0:00 [kthread]
root 22 0.0 0.0 0 0 ? S< 00:00 0:00 [kblockd/0]
root 23 0.0 0.0 0 0 ? S< 00:00 0:00 [kseriod]
root 57 0.0 0.0 0 0 ? S 00:00 0:00 [pdflush]
root 58 0.0 0.0 0 0 ? S 00:00 0:00 [pdflush]
root 59 0.0 0.0 0 0 ? S< 00:00 0:00 [kswapd0]
root 60 0.0 0.0 0 0 ? S< 00:00 0:00 [aio/0]
root 174 0.0 0.0 0 0 ? S 00:00 0:00 [mtdblockd]
root 188 0.0 0.0 0 0 ? S< 00:00 0:00 [EVB1226-SPI.0]
root 204 0.0 0.0 0 0 ? D 00:00 0:00 [swapper] ?-----------------------------------------------
root 207 5.0 0.0 0 0 ? S< 00:00 0:02 [rpciod/0]
root 284 2.5 0.5 1704 556 ? S<s 00:00 0:01 udevd --daemon
bin 926 0.3 0.3 1656 368 ? Ss 00:00 0:00 /sbin/portmap
root 960 1.5 0.6 1576 584 ? Ss 00:00 0:00 /sbin/syslogd -
root 968 0.3 0.4 1500 392 ? Ss 00:00 0:00 /sbin/klogd -x
solution:
It's due to VSP(virtual serial port) driver in the case of my kernel.
Choosing VSP as module, instead of compiling it into kernel while configure kernel, could solve the problem.
conclusion:
Just as the author of the following article said, the D state process (swapper), which is in uninterruptable sleep conditon, usually is caused by device driver.
http://hychen.wuweig.org/?p=307