On Thu, Sep 20, 2012 at 02:42:19PM -0400, Vivek Goyal wrote:
> On Thu, Sep 20, 2012 at 11:31:53AM -0700, Tejun Heo wrote:
> > Hello,
> >
> > On Wed, Sep 19, 2012 at 03:42:31PM -0400, Vivek Goyal wrote:
> > > On Thu, Sep 20, 2012 at 04:20:42AM +1000, Joseph Glanville wrote:
> > > > Hi,
> > > >
> > > > I booted the machine under bare metal to continue bisecting.
> > > > Thankfully this allowed me to locate the commit that causes the
> > > > problem.
> > > >
> > >
> > > I tested it and I am also noticing the hang. I can see this hang on
> > > dm devices also.
> > >
> > > I suspect this issue is related to bio based drivers. We exit the
> > > bypass mode in blk_init_allocated_queue() and that will be called
> > > only for request based drivers. So for bio based drivers may be
> > > we never exit the bypass mode and this issue is somehow side
> > > affect of that.
> >
> > Can you please trigger sysrq-t and post the result?
>
> Sorry, I had taken the sysrq-t output yesterday itself. Got distracted
> in other things and could never look through the code. Here it is.
>
> [ 418.685015] bash D ffff880037aa4e88 4720 2898 2847
> 0x00000080
> [ 418.685015] ffff88007c777cd8 0000000000000082 ffff880037aa4b00
> ffff88007c777fd8
> [ 418.685015] ffff88007c777fd8 ffff88007c777fd8 ffffffff81c13440
> ffff880037aa4b00
> [ 418.685015] ffff88007c777ce8 ffffffff81e05e40 ffff88007c777d18
> 000000010001d5e4
> [ 418.685015] Call Trace:
> [ 418.685015] [<ffffffff817a2fa9>] schedule+0x29/0x70
> [ 418.685015] [<ffffffff817a1570>] schedule_timeout+0x130/0x250
> [ 418.685015] [<ffffffff8140bbcb>] ? kobj_lookup+0x10b/0x160
> [ 418.685015] [<ffffffff8104a9b0>] ? usleep_range+0x50/0x50
> [ 418.685015] [<ffffffff817a16ae>] schedule_timeout_uninterruptible+0x1e/0x20
> [ 418.685015] [<ffffffff8104c310>] msleep+0x20/0x30
> [ 418.685015] [<ffffffff812ccaa8>] blkg_conf_prep+0x118/0x140
> [ 418.685015] [<ffffffff812cd400>] ? tg_set_conf_uint+0x20/0x20
> [ 418.685015] [<ffffffff812cd33a>] tg_set_conf.isra.20+0x2a/0xd0
> [ 418.685015] [<ffffffff810021ff>] ? do_signal+0x3f/0x610
> [ 418.685015] [<ffffffff812cd417>] tg_set_conf_u64+0x17/0x20
> [ 418.685015] [<ffffffff8109de6f>] cgroup_file_write+0x1bf/0x2c0
> [ 418.685015] [<ffffffff812864bc>] ? security_file_permission+0x2c/0xb0
> [ 418.685015] [<ffffffff811325cc>] vfs_write+0xac/0x180
> [ 418.685015] [<ffffffff811328fa>] sys_write+0x4a/0x90
> [ 418.685015] [<ffffffff817ab8d2>] system_call_fastpath+0x16/0x1b
I suspect we are looping in retry code because bio based queues never come
out of bypass mode.
/*
* If queue was bypassing, we should retry. Do so after a
* short msleep(). It isn't strictly necessary but queue
* can be bypassing for some time and it's always nice to
* avoid busy looping.
*/
if (ret == -EBUSY) {
msleep(10);
ret = restart_syscall();
}
Thanks
Vivek
--
To unsubscribe from this list: send the line "unsubscribe cgroups" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
