在内核中使用读写锁的死锁
在内核中使用读写锁的死锁
提问于 2015-05-20 05:23:13
我试图用读写文件操作编写一个简单的调试器。代码如下。
static ssize_t foo_read(struct file *fp, char __user *user,
size_t size, loff_t *loff)
{
ssize_t retval;
up_read(&foo_sem);
retval = simple_read_from_buffer(user, size, loff, fooBuffer,
fooBufferSize);
down_read(&foo_sem);
return retval;
}
static ssize_t foo_write(struct file *fp, const char __user *data,
size_t size, loff_t *loff)
{
ssize_t retval;
pr_debug("foo Write Funcion data %s=,size=%zu\n", data, size);
up_write(&foo_sem);
retval = simple_write_to_buffer(fooBuffer, sizeof(fooBuffer)-1, loff,
data, size);
if (retval > 0) {
fooBufferSize = size + *loff;
fooBuffer[fooBufferSize] = '\0';
}
down_write(&foo_sem);
return retval;
}并将读写锁初始化为
static DECLARE_RWSEM(foo_sem);当我编译代码并在没有锁的情况下运行时，它可以正常工作。
但是，当我使用锁运行时，程序似乎被调度程序杀死了。
[ 8640.104388] INFO: task a.out:6387 blocked for more than 120 seconds.
[ 8640.104398] Tainted: G OE 3.17.0-rc5+ #1
[ 8640.104402] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 8640.104407] a.out D ffff88007fc14580 0 6387 1 0x00000004
[ 8640.104415] ffff880075497df0 0000000000000002 ffff88007a0e9900 ffff880075497fd8
[ 8640.104422] 0000000000014580 0000000000014580 ffffffff81c1d480 ffff88007a0e9900
[ 8640.104428] ffff88007a0e9900 ffffffffa013b018 ffffffffa013b000 ffffffff00000000
[ 8640.104434] Call Trace:
[ 8640.104450] [<ffffffff8174a8a9>] schedule+0x29/0x70
[ 8640.104460] [<ffffffff8174d62d>] rwsem_down_write_failed+0x1ed/0x390
[ 8640.104472] [<ffffffff81381d03>] call_rwsem_down_write_failed+0x13/0x20
[ 8640.104482] [<ffffffff8174cf7d>] ? down_write+0x2d/0x40
[ 8640.104492] [<ffffffffa013906e>] foo_write+0x6e/0xa0 [firstmodule]
[ 8640.104503] [<ffffffff811d42f7>] vfs_write+0xb7/0x1f0
[ 8640.104513] [<ffffffff811d4e96>] SyS_write+0x46/0xb0
[ 8640.104523] [<ffffffff8174f47f>] tracesys+0xe1/0xe6回答 1
Stack Overflow用户
回答已采纳
发布于 2015-05-20 05:43:33
您正在反向使用up和down操作。当您想要访问资源时调用down，然后在访问完成后调用up。
例如：
down_read(&foo_sem);
retval = simple_read_from_buffer(user, size, loff, fooBuffer,
fooBufferSize);
up_read(&foo_sem);页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/30340881
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