On Fri, Aug 29, 2014 at 09:30:54AM +0800, Zhang, Yanmin wrote: > On 2014/8/28 23:10, Greg KH wrote: > > >On Thu, Aug 28, 2014 at 06:09:09PM +0800, Chen LinX wrote: > >>From: "Chen, LinX" <linx.z.c...@intel.com> > >> > >>When mount debugfs with no mode specifed after it's mounted, the mount > >>point mode will change to default mode(0700) even the mount operation was > >>fail, > >>this will cause some issues like can't get binder info in android. > >I don't understand, what did you do to get into this state? > > Greg, > > Thanks for your kind quick comments. The patch description can be improved. > > We hit the issue when debugging a UIWDT issue. Android framework has a good > method to detect userspace hang and reports UIWDT issues. Android uses > client/server model. Clients communicates with servers by binder. binder has > debugfs interfaces. Some files show what threads are communicating with what > other threads. If one thread is blocked for a long time, we can find the > blocking chain from the binder info. > > Since the error dumping process has no root access, booting process changes > debugfs mount dir mode to 0755. When UIWDT happens, the error dumping > process can read the info. > > Unfortunately, some other scripts at booting try to mount debugfs for many > times. > No matter if the double mounting fails or succeeds, debugfs_parse_options > changes > the root inode's mode back to the default 0700. It means the effect of > previous > mode changing to 0755 is lost. At UIWDT, the dumping process can't save binder > info to disk log files.
Then fix those other scripts, don't try to work around broken userspace scripts by changing the kernel. Sorry, I can't take this patch. greg k-h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
