这几天测试的时候发现个很奇怪的问题　如果将ＴＦ卡插到读卡里然后在插到板子上　热插拔后都可以挂载上　但是使用Ｕ盘只有第一次插上去的时候能挂载上　拔下来后　在插上就挂载不上了　驱动里可以识别到Ｕ盘已经插入　研究了MountService和Vold　最后通过查看/proc/mounts文件发现　Ｕ盘第一次插上后是正常挂载　但是拔掉后没有卸载　多么纠结的事件 主要涉及文件system/vold/DirectVolume.cpp

分析log发现　拔掉带有ＴＦ卡的读卡器时　状态是这样的

4(Mounted) -> 5(Unmounting)

5(Unmounting) -> 1(Idle-Unmounted)

1(Idle-Unmounted) -> 0(No-Media)

而U盘拔掉状态是这样的

4(Mounted) ->0(No-Media)

拔掉带有ＴＦ卡的读卡器时最后执行了这样两个函数

先执行了

handlePartitionRemoved

然后执行了

handleDiskRemoved

拔掉U盘时最后执行了函数只执行了

handleDiskRemoved

而卸载的函数是在handlePartitionRemoved里执行的所以修改handleDiskRemoved函数

修改后如下

void DirectVolume::handleDiskRemoved(const char *devpath, NetlinkEvent *evt) {
    int major = atoi(evt->findParam("MAJOR"));
    int minor = atoi(evt->findParam("MINOR"));
    char msg[255];
    SLOGD("Volume %s %s disk %d:%d removed\n", getLabel(), getMountpoint(), major, minor);
    snprintf(msg, sizeof(msg), "Volume %s %s disk removed (%d:%d)",
             getLabel(), getMountpoint(), major, minor);
    mVm->getBroadcaster()->sendBroadcast(ResponseCode::VolumeDiskRemoved,
                                             msg, false);
	if(getState() == Volume::State_Mounted) {//add by hclydao for udisk
        if (Volume::unmountVol(true, false)) {
            SLOGE("Failed to unmount volume on bad removal (%s)", 
                 strerror(errno));
            // XXX: At this point we're screwed for now
        } else {
            SLOGD("Crisis averted");
        }
	} 
    setState(Volume::State_NoMedia);
}

	if(getState() == Volume::State_Mounted) {//add by hclydao for udisk
        if (Volume::unmountVol(true, false)) {
            SLOGE("Failed to unmount volume on bad removal (%s)", 
                 strerror(errno));
            // XXX: At this point we're screwed for now
        } else {
            SLOGD("Crisis averted");
        }
	}

初步测试是没问题了

android4.0 U盘热插拔后挂载不上bug解决